The Effect of Probiotic Lactobacillus Strains on Porphyromonas gingivalis, the Etiological Factor of Periodontal Diseases—A Systematic Review

Abstract

Periodontal diseases are multifactorial, involving dysbiotic microbial communities and impaired immune responses. Porphyromonas gingivalis is considered the critical bacterium in their pathogenesis. Periodontal diseases are related to biofilm formation; therefore, their antimicrobial treatment is difficult. The review’s aim was to summarize the effect of probiotic Lactobacillus strains on P. gingivalis. A structured research of bibliographic databases was conducted according to PRISMA 2020 guidelines. We included all eligible records from 2014 to 2024. Seventy-two studies and seventeen Lactobacillus species were analyzed. According to fifty-two in vitro studies, various Lactobacillus strains affect P. gingivalis. Their ability to inhibit P. gingivalis growth and biofilm formation, auto-aggregate and co-aggregate with P. gingivalis, to alleviatie P. gingivalis-induced inflammation, to produce anti-microbial compounds and to protect gingival epithelial cells affected by P. gingivalis, are highlighted. In animal studies, Lactobacillus strains decrease oral load of P. gingivalis and control bone resorption and inflammation in experimental periodontitis. However, the results of twelve clinical trials assessing the efficacy of adjunctive probiotic therapy are ambiguous. Some of them present the ability of Lactobacillus strains to reduce P. gingivalis load in subgingival plaque, saliva, and crevicular fluid of both healthy volunteers and patients with periodontal diseases, while others show no positive impact. What is important, strain specificity is particularly emphasized. Therefore, detailed in vivo experimental models and clinical studies are necessary to verify in vitro findings, asses their actual effect on P. gingivalis in the human oral cavity, as well as make sure of their safety.

Introduction

Oral diseases pose a significant social and economic burden, affecting about 3.5 billion people worldwide and ranking among the most non-communicable diseases [1]. Following untreated caries of permanent teeth (2 billion cases), severe periodontal diseases are the second most prevalent oral diseases with approximately 1 billion cases. Over the last 30 years, the global case number of untreated oral diseases significantly increased, pointing out the need for appropriate oral health care [1].

Several pathologies can affect the oral cavity. Diseases such as dental caries and periodontal diseases are often associated with changes in the oral microbiome such as an increase or a decrease in the abundance of individual bacterial species. The oral microbiome is a community of microorganisms comprising bacteria, fungi, viruses, archaea, and protozoa from up to 1000 microbial species that colonize the human oral cavity [2]. According to eHOMD (Human Oral Microbiome Database), there are 774 species of bacteria living in the oral cavity (accessed on 9 September 2024) [3]. Typically, in a healthy microbiome, about 100 to 200 bacteria can be found. Between the microorganisms in the oral cavity, there is a symbiotic relationship that is based on mutual benefits. What is important is that the commensal bacteria control pathogenic species and prevent their adhesion to the mucosa. If this barrier is broken, infection and disease develop [4].

Periodontal diseases are multifactorial, involving dysbiotic microbial communities and impaired immune responses, contributing to the destruction of the teeth-supporting tissues [5, 6]. Porphyromonas gingivalis is considered the critical bacterium in the pathogenesis of periodontal diseases including periodontitis and alveolar bone loss, producing a variety of virulence factors, including fimbriae, endotoxins, collagenase, proteases, hemolysins, and fatty acids, that are crucial for its ability to cause inflammation and the development of periodontal diseases [7, 8]. It is a Gram-negative anaerobic bacterium that can be found in periodontal pockets, both in health and disease [9]. P. gingivalis is able to damage the tissue, invade the epithelial cells, and cause systemic diseases [10]. It can simultaneously induce the production of inflammatory mediators and downregulate the immune response of the host [11].

Periodontal diseases are related to biofilm formation [12]. Biofilm is a layer of bacteria, both Gram-positive and Gram-negative, adhering to a firm surface and growing, surrounded by a self-created, adhesive matrix [13, 14]. Biofilms can be described as a shield that protects bacteria from environmental stresses and enables them to form complex communities [15]. Biofilms are characterized by a surprising ability to adapt to a changing environment [16]. The biofilm is a predisposing factor to various oral diseases such as dental caries, gingivitis, periodontitis, and peri-implantitis [17]. Normally, the oral cavity is characterized by a diverse, nonetheless stable, oral microbiota. Any imbalance in the microbiota may lead to the proliferation of pathogenic oral microorganisms and the development of oral diseases [18]. The growth of pathogenic, Gram-negative bacteria is normally controlled by antagonistic interactions of beneficial Gram-positive, aerobic species. When these interactions are not sufficient, the loss of proper biofilm proportions begins [11]. The shift from predominantly Gram-positive bacteria to mostly Gram-negative species in the oral biofilm leads to periodontal diseases [10]. With the maturation of the biofilm, the occurrence of anaerobic pathogens increases due to environmental changes. Bacteria from the “orange complex” (Prevotella intermedia, Fusobacterium nucleatum, Campylobacter rectus, Eubacterium spp.) act as a bridge between the “early colonizers” (Gram-positive facultative anaerobic bacteria) and the “red complex” (P. gingivalis, Tannerella forsythia, and Treponema denticola). They create living conditions for highly pathogenic, strictly anaerobic bacteria from the “red complex” which are crucial for the progression of periodontal diseases and their chronicization [10, 186]. There are many similarities between periodontal diseases and peri-implant infections; however, recent molecular techniques highlight important microbial differences. The periodontal microbiota is qualitatively superior (in terms of diversity) but quantitatively inferior for some bacterial genera compared to the peri-implant microbiota [187].

Bacteria within a biofilm exhibit a high level of antibiotic resistance. Because of a favorable environment for horizontal gene transfer, antibiotic-resistant genes are easily spread amongst the inhabitants of the biofilm [19]. Moreover, penetration of the antibiotic into the biofilm is significantly hindered [16]. There are also other factors contributing to the antimicrobial tolerance of the biofilms such as the following: slow growth rate, presence of persistent bacterial cells with non-proliferative phenotype, presence of multidrug efflux pumps, and specific microenvironment that reduces susceptibility to antibiotics [20]. Consequently, antimicrobial treatment often cannot completely eliminate pathogenic bacteria within the biofilm [21].

Mechanical debridement, the traditional treatment of periodontal diseases, may be insufficient in many cases [22]. Nowadays, as an adjunct to conventional mechanical debridement, broad-spectrum antibacterial agents are mainly used to treat periodontal diseases, which can harm beneficial species essential for oral health [10]. Precise elimination of pathogens, without affecting the natural flora of the mouth, is still a problem [16]. Therefore, more targeted antimicrobial agents are needed to control pathogenic species in the polymicrobial environment of the oral cavity [10]. Currently, the use of antimicrobial peptides, plant-derived compounds, and probiotics has been proposed as potential solutions [23]. Several studies have shown that probiotics may be effective as an adjunctive therapy for periodontitis [24]. According to in vivo studies with microbiological analysis, they can significantly reduce the bacterial load of both “orange complex,” which creates living conditions for highly pathogenic, strictly anaerobic bacteria from the “red complex” and “red complex” itself [186].

To qualify as a probiotic, a live microorganism must provide beneficial effects in a host organism [25]. Probiotics are defined by WHO as “living microorganisms that, when administered in adequate amounts, exert a positive effect on the host’s health by strengthening the gut ecosystem” [26]. By definition, probiotics must meet certain requirements: they should be safe for use, able to survive the human gastrointestinal tract environment, and viable at the target site in sufficient quantities to deliver beneficial effects [27]. The list of probiotics’ useful roles in inflammatory diseases is still expanding [28]. It seems that probiotics can also be used in dentistry as adjuncts in the management of oral diseases, including periodontitis [29].

Probiotics’ ability to inhibit pathogens adhesion to host tissues, modulate immune responses, produce various antimicrobial compounds, inhibit biofilm formation, and disrupt bacterial communication are particularly relevant in dentistry [30]. Over the past two decades, the use of probiotics to fight oral diseases related to biofilms was studied, and the therapeutic potential of some lactobacilli has been reported [31]. Due to the significant genotypic, phenotypic, and ecological diversity within the genus, 261 species of Lactobacillus were reclassified into 25 genera in 2020. In this review, we will use the terms ‘Lactobacillus’ and ‘lactobacilli’ to refer to the species classified as Lactobacillus prior to March 2020 [32]. Probiotic Lactobacillus strains are able to persist and multiply in the human organism, reduce or exclude adherence of pathogens, adhere to cells, produce organic acids, bacteriocins, and hydrogen peroxide, which support the formation of a balanced microbial flora [33]. They hold “Generally Recognized As Safe” (GRAS) and “Qualified Presumption of Safety” (QPS) status, making them widely accepted as probiotics [34]. Moreover, they are nonpathogenic, noncarcinogenic, and noninvasive [35]. Lactobacilli have proven effective in treating various health conditions [33], and they are now also being considered for managing oral diseases, including periodontal diseases.

The aim of this review was to summarize the effect of probiotic Lactobacillus strains on Porphyromonas gingivalis, the main etiological factor of periodontal diseases.

Material and Methods

We conducted the analysis following the PRISMA 2020 guidelines (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) [36]. Our review was based on three databases: PubMed, Web of Science and Scopus. We included records from 2014 to 2024.

To define the search objectives we utilized MeSH (Medical Subject Heading) terms and keywords combined with Boolean operators (“and”). Due to the changes in the classification of lactobacilli, we used both the old genus name—Lactobacillus and 23 newly classified genera. Results were found for four genera in particular: Lactiplantibacillus, Lacticaseibacillus, Levilactobacillus, Ligilactobacillus, Limosilactobacillus, and Latilactobacillus.

Our search strategy included the following keyword combinations: (1) Lactobacillus AND Porphyromonas gingivalis, (2) Lactiplantibacillus AND Porphyromonas gingivalis, (3) Lacticaseibacillus AND Porphyromonas gingivalis, (4) Levilactobacillus AND Porphyromonas gingivalis, (5) Ligilactobacillus AND Porphyromonas gingivalis, (6) Limosilactobacillus AND Porphyromonas gingivalis, (7) Latilactobacillus AND Porphyromonas gingivalis. These terms most accurately aligned with the goals of our study.

The selection process was divided into two stages: (1) title and abstract screening and (2) full-text examination. Articles meeting the following inclusion criteria were considered: (1) original research articles, (2) human intervention studies (clinical trials), animal studies, laboratory or in vitro studies, (3) articles published in English in a peer-reviewed journal. The exclusion criteria were as follows: (1) publications that do not include original data (e.g., meta-analyses), (2) studies not in English, (3) full text not available.

Titles and abstracts of the initial search were downloaded and assessed for relevance. For additional review, we obtained full publications from relevant studies. The studies were assessed by two independent reviewers, who used the above-presented criteria.

An independent search of the database was conducted by two researchers in order to find studies meeting the inclusion criteria and not meeting the exclusion criteria. Any discrepancies between these reviewers were discussed and resolved with the senior researcher. We selected studies that explored the effects of lactobacilli with probiotic properties on Porphyromonas gingivalis, the key pathogen of periodontal diseases.

Eight hundred and thirty-four records were found, but only seventy-two met the PRISMA’s guidelines. We excluded duplications and studies that did not meet the criteria of inclusion. Additionally, six studies were not available as full-size text, and three were not written in English. The selection process was presented in Fig. 1.

Fig. 1.

Studies included in this review—the selection process

Among the studies analyzed, there were fifty-two in vitro studies (fourteen in vitro studies on cell lines), eight animal studies, and twelve clinical trials. Based on these studies, the influence of seventeen Lactobacillus species on P. gingivalis was analyzed.

Two researchers independently assessed the quality of the studies which were included in the systematic review. Considering the type of study, the following tools were used: the Revised Cochrane risk-of-bias tool for randomized trials (RoB2), the Risk Of Bias In Non-randomized Studies of Interventions tool (ROBINS-I), SYRCLE’s risk-of-bias tool for animal studies, and the Quality Assessment Tool For In Vitro Studies (QUIN Tool) [188–191]. Any discrepancies in the assessment were discussed by both reviewers to reach consensus.

Results

Levilactobacillus Brevis

Levilactobacillus brevis (formerly known as Lactobacillus brevis) is a microaerophilic, Gram-positive, obligately heterofermentative lactic acid bacterium with probiotic properties [37]. It grows well in low pH and at 30 °C and can be found both in fermented products (dairy food, fermented vegetables) and the human gastrointestinal tract [38, 39]. The safety of L. brevis has been scientifically confirmed. It has Generally Recognized As Safe status and has been approved as safe to add to food (Qualified Presumption of Safety (QPS)) [40]. As L. brevis has antimicrobial properties against some pathogenic bacteria, it most likely produces compounds with antibacterial activity [41]. Moreover, L. brevis is able to improve the microbiota condition and modulate the immune system, alleviating inflammation [42]. Strains of L. brevis have various probiotic properties such as the following: the ability of co-aggregation and adherence to oral epithelial cells [43]. Some strains of L. brevis produce only small amounts of lactic acid making them suitable for oral application, as lactic acid is able to weaken the enamel [43, 44]. Moreover, some strains produce hydrogen peroxide [43]. L. brevis is resistant to various antibiotics, allowing it to be used during antibiotic therapy to support recovery and maintain microbial balance [45].

In the case of L. brevis, 7 studies were analyzed in the review: 6 in vitro studies (2 in vitro studies on cell lines) and 1 clinical trial. A summary of studies available in the literature concerning the impact of L. brevis strains on P. gingivalis is presented in Table 1.

Table 1.

The studies that concern the impact of Levilactobacillus brevis strains on Porphyromonas gingivalis

Authors, year	Type of study	P. gingivalis strain	L. brevis strain	Results
Maekawa et al., 2014 [46]	In vitro, model: THP-1 cells	N/A	CD2	Soluble L. brevis CD2 extracts inhibit the production of inflammatory mediators in THP-1 cells activated by P. gingivalis-derived LPS (p < 0.05)
Fang et al., 2018 [43]	In vitro	GIM 1.851	BBE-Y52	L. brevis BBE-Y52 reduces P. gingivalis GIM 1.851 aggregation. It produces 0.06–0.15 mM hydrogen peroxide, can auto-aggregate and co-aggregate
Mohd-Zubri et al., 2022 [47]	In vitro	ATCC 33277	FT 6	L. brevis FT 6 can inhibit the growth of P. gingivalis ATCC 33277 (inhibition zone (mean ± SD (mm)): 10.44 ± 1.10; MIC = 50 µl/µl, MBC = 50 µl/µl, biofilm reduction at MIC concentration: 78.12%). It can auto-aggregate (auto-aggregation rate: > 80%) and co-aggregate with P. gingivalis (co-aggregation rate: 65–70%)
Choi et al., 2021 [48]	In vitro	KCTC 5352	Unknown	L. brevis can inhibit the growth of P. gingivalis KCTC 5352 (inhibition zone (mean ± SD): 1.9 ± 0.0 mm)
Lai et al., 2021 [49]	In vitro	ATCC 33277	18 strains	6 of 18 L. brevis strains can inhibit the growth of P. gingivalis ATCC 33277
Pudgar et al., 2021 [50]	Clinical trial	N/A	CECT7480	When compared to placebo, 3-month adjunctive treatment with L. brevis CECT7480 and L. plantarum CECT7481 (probiotic gel: 6.0 × 109 CFU/ml of each bacterium; probiotic lozenges: 1.2 × 109 CFU/ml of each bacterium) in patients with chronic periodontitis reduces the number of P. gingivalis in subgingival microbiologic samples after scaling and root planning
Mahdizade Ari et al., 2024 [51]	In vitro, model: HGFC	ATCC 33277	205	L. brevis 205 can form biofilms, aggregate and co-aggregate with P. gingivalis ATCC 33277 (co-aggregation rate = 7.15%) L. brevis 205 introduced before P. gingivalis significantly reduces its ability to produce biofilms (HGFC model)

N/A not applicable, HGFC human gingival fibroblast cells, THP-1 human leukemia monocytic cell line, SD standard deviation, MIC minimum inhibitory concentration, MBC minimum bactericidal concentration, LPS lipopolysaccharide, CFU colony-forming unit

Lactobacillus Acidophilus

Lactobacillus acidophilus is a microaerobic, Gram-positive, homofermentative lactic acid bacterium that grows optimally at pH 5.5–6.0 and 35–38 °C. Compared with other probiotic bacteria, L. acidophilus demonstrates greater resistance to acid and bile salt, along with the ability to survive and grow in an environment unsuitable for other lactic acid bacteria [52, 53]. It is well-known for its beneficial probiotic properties and is commonly used in the dairy industry [54]. As a dietary supplement, L. acidophilus is among the most commonly recommended microorganisms [55]. It has various essential properties such as tolerance to low pH, antimicrobial activity, bile resistance, lactase activity, and adhesion to human cells. Strains of L. acidophilus are able to produce lactic acid and bacteriocins with antimicrobial properties [56]. Moreover, they can regulate immune responses, prevent and treat infections, and regulate the balance of the intestinal flora [57]. The beneficial effects of L. acidophilus have been documented in various clinical situations.

In the case of L. acidophilus, 8 studies were analyzed in the review: 6 in vitro studies (3 in vitro studies on cell lines) and 2 animal studies. A summary of studies available in the literature that concern the impact of L. acidophilus strains on P. gingivalis is presented in Table 2.

Table 2.

The studies that concern the impact of Lactobacillus acidophilus strains on Porphyromonas gingivalis

Authors, year	Type of study	P. gingivalis strain	L. acidophilus strain	Results
Ma et al., 2018 [58]	In vitro	ATCC 33277	FomA and pMG36e	L. acidophilus FomA (recombinant strain expressing FomA, a receptor protein of Fusobacterium nucleatum used in co-aggregation) and L. acidophilus pMG36e (strain containing an empty plasmid pMG36e) can inhibit the growth of P. gingivalis ATCC 33277 L. acidophilus FomA has a significantly better ability to adhere than L. acidophilus pMG36e
Albuquerque-Souza et al., 2018 [59]	In vitro, model: GEC	W83 and ATCC 33277	LA-5	L. acidophilus LA-5/P. gingivalis W83 co-infection maintains GECs viability, reduces P. gingivalis W83 adhesion and invasion to GECs L. acidophilus LA-5/P. gingivalis ATCC 33277 co-infection increases GECs viability, reduces P. gingivalis ATCC 33277 adhesion to GECs, and does not alter its invasion
			NCFM	L. acidophilus NCFM/P. gingivalis W83 co-infection maintains GECs viability and reduces P. gingivalis W83 adhesion and invasion to GECs L. acidophilus NCFM/P. gingivalis ATCC 33277 co-infection maintains GECs viability, reduces P. gingivalis ATCC 33277 adhesion, and does not alter its invasion
Zhao et al., 2019 [60]	In vitro, model: HGEC	ATCC 33277	ATCC 4356	In dose dependent manner L. acidophilus ATCC 4356 protects the proliferation of HGECs affected by P. gingivalis ATCC 33277 In dose dependent manner L. acidophilus ATCC 4356 reduces the proapoptotic effect of P. gingivalis ATCC 33277 on HGECs
Chen et al., 2020 [61]	In vitro	BCRC 17689, BCRC 17688	TYCA02	Viable, but not heat killed, L. acidophilus TYCA02 can strongly inhibit the growth of P. gingivalis BCRC 17689 and BCRC 17688 (inhibition zone: 2–3 cm)
Ishikawa et al., 2020 [62]	In vitro, model: multi- and mono-species biofilms, GEC	W83 and ATCC 33277	LA-5	In mono-species biofilms L. acidophilus LA5 CFS does not change the number of P. gingivalis cells In multi-species biofilm, L. acidophilus LA5 CFS lowers the abundance of P. gingivalis ATCC 33277 (p < 0.05) but not P. gingivalis W83; L. acidophilus LA5 living cells affect both strains of P. gingivalis (p < 0.05) L. acidophilus LA5 CFS decreases the expression of various virulence-associated factors of P. gingivalis ATCC 33277 and W83 both in biofilms and under GECs co-infection
Lai et al., 2021 [49]	In vitro	ATCC 33277	27 strains	15 of 27 L. acidophilus strains can inhibit the growth of P. gingivalis ATCC 33277
You et al., 2022 [63]	In vivo, animal model: dog	N/A	MJCD175	4-week treatment with L. acidophilus MJCD175 (108–109 CFU, daily oral administration) significantly decreases DNA copies of P. gingivalis in intraoral swab samples
Cataruci et al., 2024 [64]	In vivo, animal model: mouse, experimental periodontitis	W83 and ATCC 33277	LA-5	Oral administration of L. acidophilus LA-5 elevates bone volume (mean: 26.7%) and decreases bone porosity (mean: 73.27%) in mice (experimental periodontitis caused by inoculated bacteria, including P. gingivalis W83 and ATCC 33277)

N/A not applicable, GEC gingival epithelial cell, HGEC human gingival epithelial cell, CFS cell-free supernatant, CFU colony-forming unit

Lacticaseibacillus Rhamnosus

Lacticaseibacillus rhamnosus (old name: Lactobacillus rhamnosus) is a facultatively anaerobic, Gram-positive, facultatively heterofermentative, lactic acid bacterium with antimicrobial properties that can be found in the human gastrointestinal tract and dairy products [65]. Strains of L. rhamnosus are widely used as probiotics, both in food production and in the prevention and treatment of numerous diseases such as antibiotic-associated diarrhea and inflammation-associated diseases [66]. L. rhamnosus has a remarkable ability to adapt to diverse ecological niches and is resistant to low pH and bile [67, 68]. It is able to colonize the epithelial cells, modulate the microbiota, and strengthen the immune system [69]. Strains of L. rhamnosus can secrete antimicrobial compounds such as lactic acid, bacteriocins, and biosurfactant with antibiofilm properties [70–72]. It holds “Generally Recognized As Safe (GRAS)” status and is added to the list of “Qualified Presumption of Safety” (QPS) [73, 74].

In the case of L. rhamnosus, 21 studies were analyzed in the review: 18 in vitro studies (7 in vitro studies on cell lines) and 3 clinical trials. A summary of studies available in the literature that concern the impact of L. rhamnosus strains on P. gingivalis is presented in Table 3.

Table 3.

The studies that concern the impact of Lacticaseibacillus rhamnosus strains on Porphyromonas gingivalis

Authors, year	Type of study		P. gingivalis strain	L. rhamnosus strain	Results
Mendi et al., 2016 [24]		In vitro, model: G-MSSC	ATCC 33277	ATCC9595	L. rhamnosus ATCC9595 modulates inflammatory signals, induces CXCL8 secretion in G-MSSCs, and introduces P. gingivalis ATCC 33277 to immune system L. rhamnosus ATCC9595 can co-aggregate with P. gingivalis
Albuquerque-Souza et al., 2018 [59]	In vitro, model: GEC		W83 and ATCC 33277	Lr-32	L. rhamnosus Lr-32/P. gingivalis W83 co-infection maintains GECs viability and reduces P. gingivalis adhesion and invasion to GECs L. rhamnosus Lr-32/P. gingivalis ATCC 33277 co-infection increases GECs viability, reduces P. gingivalis adhesion to GECs, and does not alter its invasion L. rhamnosus Lr-32/P. gingivalis (both W83 and ATCC 33277) co-infection does not change IL-1beta production, but decreases TNF-alfa and increases CXCL8 production
				HN001	L. rhamnosus HN001/P. gingivalis W83 co-infection maintains GECs viability, reduces P. gingivalis adhesion, and does not alter its invasion L. rhamnosus HN001/P. gingivalis ATCC 33277 co-infection maintains GECs viability, reduces P. gingivalis adhesion, and does not alter its invasion
Morales et al., 2018 [75]	Clinical trial		N/A	SP1	There is no significant difference in the percentage of P. gingivalis and total cultivable microbiota from subgingival plaque samples between the 3-month adjunctive therapy with L. rhamnosus SP1 (2 × 107 CFU/day) and only scaling and root planning
Alanzi et al., 2018 [76]	Clinical trial		N/A	GG	When compared to placebo, 4-week treatment with L. rhamnosus GG and Bifidobacterium lactis BB-12 lozenges in children reduces the microbial counts of P. gingivalis in the dental plaque (p < 0.001)
Gatej et al., 2018 [77]	In vitro		ATCC 33277	GG	L. rhamnosus GG does not have an antimicrobial activity against P. gingivalis ATCC 33277
Chen et al., 2020 [61]	In vitro		BCRC 17689 and BCRC 17688	CT-53	Viable L. rhamnosus CT-53 has a strong antimicrobial activity against P. gingivalis BCRC 17689, BCRC 17688 (inhibition zone: 2–3 cm). Heat-killed L. rhamnosus CT-53 can inhibit the growth of P. gingivalis (inhibition rate: 60–80%)
				F-1	Viable L. rhamnosus F-1 has a strong antimicrobial activity against P. gingivalis BCRC 17689, BCRC 17688 (inhibition zone: 2–3 cm). Heat-killed L. rhamnosus F-1 can inhibit the growth of P. gingivalis (inhibition rate: 60–80%)
Moman et al., 2020 [78]	In vitro		ATCC 33277	ATCC 7469	L. rhamnosus ATCC 7469 can inhibit the growth of P. gingivalis ATCC 33277
Ishikawa et al., 2020 [62]	In vitro, model: multi- and mono-species biofilms		W83 and ATCC 33277	HN001	In mono-species biofilms L. rhamnosus HN001 CFS does not change the number of P. gingivalis cells In multi-species biofilms, L. rhamnosus HN001 CFS lowers the abundance of P. gingivalis ATCC 33277 (p < 0.05) but not W83 In multi-species biofilm, L. rhamnosus HN001 living cells lower the abundance of P. gingivalis ATCC 33277 and W83 (p < 0.05)
Lai et al., 2021 [49]	In vitro		ATCC 33277	13 strains	13 of 13 L. rhamnosus strains can inhibit the growth of P. gingivalis ATCC 33277
Choi et al., 2021 [48]	In vitro		KCTC 5352	GG	L. rhamnosus GG can inhibit the growth of P. gingivalis KCTC 5352 (inhibition zone: 1.4 ± 0.5 mm)
Michaylova et al., 2021 [79]	In vitro		DSM 20709	I-1/13, I-4/1, NBIMCC 507	Milk fermented with L. rhamnosus I-1/13 (but not I-4/1, NBIMCC 507) can inhibit the growth of P. gingivalis DSM 20709. Freeze-dried preparations of all strains can inhibit the growth of P. gingivalis
Vale et al., 2021 [80]	In vitro, model: GEC		ATCC 33277	Lr-32	L. rhamnosus Lr-32 lysate upregulates the transcription of inflammatory mediators (IL-1 beta, TNF-alpha, IL6, CXCL8) in GECs challenged with P. gingivalis ATCC 33277. Cells’ components of L. rhamnosus Lr-32 can increase GEC’s response to P. gingivalis Both L. rhamnosus Lr-32 lysate and spent media can inhibit the growth of P. gingivalis
Kim et al., 2022 [81]	In vitro, model: HGF-1		N/A	MG4706, MG4709, MG4711	L. rhamnosus MG4706, MG4709, and MG4711 can inhibit the production of IL-1beta, IL6, MMP8, and MMP9 in HGF-1 stimulated by P. gingivalis-derived LPS
Kim et al., 2022 [82]	In vitro, model: RAW 264.7 cells		N/A	GG	Bacterial lysate from L. rhamnosus GG can inhibit inflammatory responses in RAW 264.7 cells induced by P. gingivalis-derived LPS
Thananimit et al., 2022 [83]	In vitro		ATCC 33277	SD4	Short-chain fatty acids of L. rhamnosus SD4 can inhibit the growth of P. gingivalis ATCC 33277 (inhibition zone (mean ± SD): 14.0 ± 0.0 mm; MIC (mean ± SD): 368.8 ± 0.0 µg/mL)
				SD11	Short-chain fatty acids of L. rhamnosus SD11 can inhibit the growth of P. gingivalis ATCC 33277 (inhibition zone (mean ± SD): 17.0 ± 0.4 mm; MIC (mean ± SD): 358.6 ± 0.0 µg/mL)
				GG	Short-chain fatty acids of L. rhamnosus GG can inhibit the growth of P. gingivalis ATCC 33277 (inhibition zone (mean ± SD): 15.5 ± 0.4 mm)
Mohd-Zubri et al., 2022 [47]	In vitro		ATCC 33277	ATCC 7469	L. rhamnosus ATCC 7469 can inhibit the growth of P. gingivalis ATCC 33277 (inhibition zone (mean ± SD (mm)): 10.64 ± 0.44 mm; MIC = 25 μl/μl, MBC = 25 µl/µl, biofilm reduction at MIC concentration: 76.63%). It can auto-aggregate (auto-aggregation rate: > 70%) and co-aggregate with P. gingivalis (co-aggregation rate: 65–70%)
Van Holm et al., 2023 [84]	In vitro		ATCC 33277	GG	L. rhamnosus GG can inhibit the growth of P. gingivalis ATCC 33277 (inhibition ratio (± SD): 0.672 ± 0.071)
Patil et al., 2023 [85]	In vitro		ATCC 43037	GG	L. rhamnosus ATCC 53103 can inhibit the growth of P. gingivalis ATCC 43037
Oda et al., 2023 [86]	Clinical trial		N/A	L8020	When compared to placebo, 84-day treatment with L. rhamnosus L8020 (yogurt) in patients with an intellectual disability, it reduces the relative abundance of P. gingivalis in dental plaque
Van Holm et al., 2024 [87]	In vitro, model: human oral keratinocytes and THP-1 cells		ATCC 33277	T7	L. rhamnosus T7 reduces the prevalence of periodontal pathobionts (including P. gingivalis ATCC 33277) on the keratinocytes by ~ 40% L. rhamnosus T7 significantly suppresses IL-8 and TNF-alpha production and increases IL-10 production by THP-1 cells stimulated by P. gingivalis-derived LPS
				GG	L. rhamnosus GG reduces the prevalence of periodontal pathobionts (including P. gingivalis ATCC 33277) on the keratinocytes by < 20% L. rhamnosus GG and T7 can inhibit the growth of P. gingivalis
Mahdizade Ari et al., 2024 [51]	In vitro, model: HGFC		ATCC 33277	195	L. rhamnosus 195 can form biofilms, aggregate and co-aggregate with P. gingivalis ATCC 33277 (5.12%). L. rhamnosus 195 introduced before P. gingivalis ATCC 33277, significantly reduces its ability to produce biofilm (HGFC model)

N/A not applicable, THP-1 human leukemia monocytic cell line, RAW 264.7 murine macrophage cell line, HGFC human gingival fibroblast cells, GECs gingival epithelial cells, G-MSSCs gingival stromal stem cells, CFS cell-free supernatant, CFU colony-forming unit, MIC minimum inhibitory concentration, MBC minimum bactericidal concentration, LPS lipopolysaccharide, CXCL8 interleukin 8, IL-8 interleukin 8, IL-10 interleukin 10, IL-6 interleukin 6, IL-1beta interleukin 1-beta, TNF-alpha tumor necrosis factor-alpha, MMP8 matrix metalloproteinase 8, MMP9 matrix metalloproteinase 9

Limosilactobacillus Fermentum

Limosilactobacillus fermentum (old name: Lactobacillus fermentum) is a Gram-positive, obligately heterofermentative lactic acid bacterium with a promising probiotic potential [88]. It is normally found in the human gastrointestinal tract [89]. L. fermentum can survive in low pH [90]. L. fermentum, known for its ability to form biofilms, affects the immune system and produces metabolites such as bacteriocins and bio-surfactants that can inhibit pathogens [91]. It can regulate the levels of different cytokines and interact with immune cells, and therefore act as an immunomodulatory and anti-inflammatory agent [92]. The antimicrobial properties of L. fermentum strains can be attributed to the production of organic acids and antimicrobial peptides. Moreover, some strains can provide protection against oxidative stress [93]. Beneficial effects of several strains of L. fermentum have been described in many researches, both in preclinical studies and human trials [93]. L. fermentum has a potential role in diseases related to inflammation such as intestinal inflammation, hepatic injury, and infections of the respiratory tract [92].

In the case of L. fermentum, 6 studies were analyzed in the review: 5 in vitro studies and 1 animal study. A summary of studies available in the literature that concern the impact of L. fermentum strains on P. gingivalis is presented in Table 4.

Table 4.

The studies that concern the impact of Limosilactobacillus fermentum strains on Porphyromonas gingivalis

Authors, year	Type of study	P. gingivalis strain	L. fermentum strain	Results
Hirasawa et al.,. 2020 [94]	In vitro	FDC 381 and ATCC 33277	2 strains	2 strains of L. fermentum isolated from saliva of periodontally healthy people can inhibit the growth of P. gingivalis FDC 381 and ATCC 33277 (inhibition zone > 12 mm)
Lai et al., 2021 [49]	In vitro	ATCC 33277	21 strains	9 of 21 L. fermentum strains can inhibit the growth of P. gingivalis ATCC 33277
Zhang et al., 2021 [95]	In vivo, animal model: rat, experimental periodontitis	ATCC 33277	CCFM1139	L. fermentum CCFM1139 reduces the levels of P. gingivalis in the oral cavity (p < 0.05) and decreases the levels of IL-1beta, TNF-alpha, IL-8 in periodontal tissue (p < 0.05) in rats with periodontitis induced with P. gingivalis ATCC 33277 and F. nucleatum ATCC25586
Mann et al., 2021 [96]	In vitro	KCOM 2796	OK	L. fermentum OK can inhibit the growth of P. gingivalis KCOM 2796, produce hydrogen peroxide and co-aggregate with P. gingivalis
Kawai et al., 2022 [97]	In vitro	ATCC 33277	ALAL020	A dipeptide from L. fermentum ALAL020 (cyclo (Hyp-Leu)) can inhibit the growth of P. gingivalis ATCC 33277 (MIC = 2.5 g/L, MBC ≤ 5 g/L, no tissue toxicity at 10 g/L) L. fermentum ALAL020 has a very strong antimicrobial activity against P. gingivalis ATCC 33277
Van Holm et al., 2023 [84]	In vitro	ATCC 33277	V001	L. fermentum V001 cannot inhibit the growth of P. gingivalis ATCC 33277

MIC minimum inhibitory concentration, MBC minimum bactericidal concentration, IL-1beta interleukin 1-beta, IL-8 interleukin 8, TNF-alpha tumor necrosis factor-alpha

Lactiplantibacillus Plantarum

Lactiplantibacillus plantarum (old name: Lactobacillus plantarum) is a microaerophilic, Gram-positive, facultatively heterofermentative lactic acid bacterium [98]. Unlike other Lactobacillus species, L. plantarum can be found in various foods and on the mucous membranes of animals and humans [99]. It is characterized by good acid and cold resistance and a moderate ability to produce organic acids [100]. L. plantarum produces various substances such aslactic acid, diacetyl, hydrogen peroxide, and bacteriocin [101]. Its physiological functions and beneficial health properties make it one of the most common probiotics [98]. L. plantarum is known for its antimicrobial properties and inhibitory effect on various pathogenic bacteria [102]. Moreover, it has the ability to influence the immune system and alleviate inflammation [103]. It is used both in the food industry and in human medicine. It is used as a part of the treatment of various diseases such as cardiovascular diseases, diabetes, liver disorders, urogenital disorders, and cancer [104]. Postbiotic metabolites of L. plantarum have anti-biofilm activity and act against oral pathogens such as P. gingivalis [105]. L. plantarum has the Generally Recognized As Safe status and has the Qualified Presumption of Safety (QPS) status [106, 107].

In the case of L. plantarum, 13 studies were analyzed in the review: 13 in vitro studies (4 in vitro studies on cell lines). A summary of studies available in the literature that concerns the impact of L. plantarum strains on P. gingivalis is presented in Table 5.

Table 5.

The studies that concern the impact of Lactiplantibacillus plantarum subsp. plantarum strains on Porphyromonas gingivalis

Authors, year	Type of study	P. gingivalis strain	L. plantarum strain	Results
Khalaf et al., 2016 [108]	In vitro	ATCC 33277 and W50	44,048 and NC8	L. plantarum 44,048 and NC8 can inhibit the growth of P. gingivalis ATCC 33277 and W50 A two-peptide bacteriocin from L. plantarum NC8 (PLNC8 αβ) is effective against P. gingivalis
Lin et al., 2021 [101]	In vitro	ATCC 33277	NRIC 149	Plantaricin 149 from L. plantarum NRIC 149 (Pln 149) can inhibit the growth of P. gingivalis ATCC 33277 (MIC and MBC: 125 µg/ml). Pln 149 strongly inhibits P. gingivalis biofilm formation
Lee et al., 2021 [109]	In vitro	ATCC 33277	5 strains	L. plantarum lipoteichoic acid (Lp.LTAs) has an anti-biofilm activity, but does not affect P. gingivalis biofilms
Lai et al., 2021 [49]	In vitro	ATCC 33277	21 strains	16 of 21 L. plantarum strains can inhibit the growth of P. gingivalis ATCC 33277
Kim et al., 2022 [81]	In vitro, model: RAW 264.7 cells	NA	ATCC 14917	Bacterial lysate from L. plantarum ATCC 14917 can inhibit inflammatory responses in RAW 264.7 cells induced by P. gingivalis-derived LPS
Karaca et al., 2022 [110]	In vitro	ATCC 33277, AHN 24155	EIR/IF-1	Exopolysaccharides (EPSs) from L. plantarum EIR/IF-1 postbiotics have antibiofilm properties against oral bacteria. They inhibit auto-aggregation and co-aggregation of bacteria and their hydrocarbon binding
Lin et al., 2022 [111]	In vitro	BCRC 17689, BCRC 17688	LPL28	Postbiotics of L. plantarum LPL28 have an antimicrobial effect against P. gingivalis BCRC 17689 and BCRC 17688
Mohd-Zubri et al., 2022 [47]	In vitro	ATCC 33277	FT 12	L. plantarum FT 12 can inhibit the growth of P. gingivalis ATCC 33277 (inhibition zone (mean ± SD): 10.22 ± 0.49 mm, MIC = 25 μl/μl, MBC = 25 µl/µl, biofilm reduction at MIC concentration: 76.12%). It can autoaggregate (auto-aggregation rate: > 80%) and co-aggregate with P. gingivalis (co-aggregation rate: 65–70%)
Van Holm et al., 2023 [84]	In vitro	ATCC 33277	WCFS1	L. plantarum WCFS1 can inhibit the growth of P. gingivalis ATCC 33277 (inhibition ratio (± SD): 0.931 ± 0.089)
Butrungrod et al., 2023 [105]	In vitro	ATCC 33277	PD18	A postbiotic metabolite from L. plantarum PD18 (PD18 PM) has an antagonistic effect against P. gingivalis ATCC 33277 and an anti-biofilm activity (biofilm inhibition rate: PD18 PM = 89.68%; diluted PD18 (dilution 1:2) = 90.24%)
Choi et al., 2023 [112]	In vitro, model: RAW 264.7 cells	NA	ATCC 14917	Genomic DNA of L. plantarum ATCC 14917 can inhibit inflammatory responses in RAW264.7 cells stimulated by P. gingivalis-derived LPS
Van Holm et al., 2024 [87]	In vitro, model: human oral keratinocytes	ATCC 33277	DSM 33662	L. plantarum DSM 33662 cannot reduce the prevalence of pathobionts on the keratinocytes (including P. gingivalis ATCC 33277) L. plantarum DSM 33662 does not have any antimicrobial activity against P. gingivalis ATCC 33277
Mahdizade Ari et al., 2024 [51]	In vitro, model: HGFC	ATCC 33277	42	L. plantarum 42 can form biofilms, aggregate, co-aggregate with P. gingivalis ATCC 33277 (22.7%) and increase IL-10 levels L. plantarum 42 introduced before P. gingivalis, significantly reduces its ability to produce biofilms (HGFC model) L. plantarum 42 has the ability to inhibit the transcription of P. gingivalis genes involved in colonization, aggregation, interaction, and biofilm formation
			156	L. plantarum 156 can form biofilms, aggregate and co-aggregate with P. gingivalis ATCC 33277 (8.5%) L. plantarum 156 introduced before P. gingivalis significantly reduces its ability to produce biofilms (HGFC model)

RAW 264.7 murine macrophage cell line, HGFC human gingival fibroblast cell, MIC minimum inhibitory concentration, MBC minimum bactericidal concentration, LPS lipopolysaccharide, SD standard deviation, IL-10 interleukin 10

Limosilactobacillus Reuteri

Limosilactobacillus reuteri (old name: Lactobacillus reuteri) is a gram-positive, obligately heterofermentative lactic acid bacterium that is considered a microorganism with probiotic properties [113]. It normally colonizes the gastrointestinal tract, which can explain its great probiotic properties [114]. L. reuteri is known for its tolerance to low pH, salt, and ethanol as well as for a wide temperature range [115]. Various mechanisms are responsible for its ability to effectively inhibit the growth of pathogenic microorganisms and change the host’s composition of commensal microbiota [116]. The antibacterial activity of L. reuteri depends mainly on reuterin, a low molecular bacteriocin with antimicrobial properties produced by glycerol fermentation [117]. Reuterin is a mixture consisting of various forms of 3-hydroxypropionaldehyde (3-HPA). The antimicrobial mechanism involves the transformation of 3-HPA into a cytotoxic electrophile, acrolein [114]. Moreover, L. reuteri produces other substances with antimicrobial properties such as the following: lactic acid, ethanol, reutericyclin, and acetic acid [114]. Due to its immunomodulatory and anti-inflammatory properties, L. reuteri can influence the immune system of the host [118]. Some strains are able to decrease pro-inflammatory cytokines’ levels and promote the development and function of regulatory T cells [114]. Supplementation with L. reuteri may be a promising approach for the prevention and treatment of various inflammatory diseases affecting the gut and other tissues [114]. The safety of L. reuteri in humans has been widely studied in various populations including infants, children, and HIV-positive patients. According to the results, even high doses of L. reuteri are safe and well tolerated [116, 119–121].

In the case of L. reuteri, 22 studies were analyzed in the review: 18 in vitro studies (7 in vitro studies on cell lines) and 4 clinical trials. A summary of studies available in the literature that concern the impact of L. reuteri strains on P. gingivalis was presented in Table 6.

Table 6.

The studies that concern the impact of Limosilactobacillus reuteri strains on Porphyromonas gingivalis

Authors, year	Type of study	P. gingivalis strain	L. reuteri strain	Results
Jang et al., 2016 [122]	In vitro	ATCC 33277	unknown	L. reuteri can inhibit the growth of P. gingivalis ATCC 33277 (growth inhibition > 95%) and reduces the production of hydrogen sulfide and methyl mercaptan by P. gingivalis
Albuquerque-Souza et al., 2018 [59]	In vitro, model: GEC	ATCC 33277, W83	DSM 17938 DSM 17938	L. reuteri DSM 17938/P. gingivalis W83 co-infection maintains GECs viability, does not alter P. gingivalis adhesion to GECs and reduces its invasion L. reuteri DSM 17938/P. gingivalis ATCC 33277 co-infection maintains GECs viability, reduces P. gingivalis adhesion to GECs, and does not alter its invasion
Widyarman et al., 2018 [123]	In vitro, model: HaCat cells	ATCC 33277	ATCC-55730	L. reuteri ATCC-55730 (glycerol added) reduces the production of IL-8 and human-beta-defensin-2 by HaCat cells exposed to P. gingivalis ATCC 33277
Galofré et al., 2018 [124]	Clinical trial	N/A	ATCC PTA 5289	30-day therapy with L. reuteri ATCC PTA 5289 in patients with mucositis or peri-implantitis leads to significant reduction in P. gingivalis counts in crevicular fluid (p = 0.031) at 30 days and 90 days
Geraldo et al., 2020 [125]	In vitro	ATCC 33277	ATCC PTA 5289 and DSM 17938	Both live L. reuteri and its cell-free culture supernatant reduce the number of P. gingivalis cells ATCC 33277, leading to 76.81% and 86.6% CFU/mL decrease, respectively
Chen et al., 2020 [61]	In vitro	BCRC 17689, BCRC 17688	GL-104	Viable L. reuteri GL-104 has a strong antimicrobial activity against P. gingivalis BCRC 17689, BCRC 17688 (inhibition zone: 1–2 cm). Heat-killed L. reuteri GL-104 can inhibit the growth of P. gingivalis (inhibition rate: 60–80%)
Ishikawa et al., 2020 [62]	In vitro	ATCC 33277, W83	DSM 17938	In mono-species biofilms, L. reuteri DSM 17938 CFS does not change the number of P. gingivalis cells In multi-species biofilm, L. reuteri DSM 17938 CFS lowers the abundance of P. gingivalis ATCC 33277 (p < 0.05) but not W83 In multi-species biofilm, L. reuteri DSM 17938 living cells lower the abundance of P. gingivalis ATCC 33277 and W83 (p < 0.05)
Han et al., 2020 [126]	In vitro, model: MSC	ATCC 33277	ATCC 11284	Reuterin from L. reuteri ATCC 11284 neutralizes LPS in P. gingivalis ATCC 33277, inhibits inflammation and promotes wound healing, and maintains homeostatis of MSCs
Elsadek et al., 2020 [127]	Clinical trial	N/A	DSM-17938, ATCC PTA5289	When compared to only root surface debridement, 3-week adjunctive treatment with L. reuteri (2 × 108 CFU/tablet (DSM-17938 and ATCC PTA5289), 2 tablets/day) in type 2 diabetic patients reduces P. gingivalis counts in subgingival plaque
Jebin et al., 2021 [128]	Clinical trial	N/A	UBLRu-87	When compared to only scaling and root planing, 1-month adjunctive treatment with L. reuteri UBLRu-87 tablet (0.5 × 109 CFU) leads to a greater reduction in P. gingivalis levels in subgingival plaque at 1 month and 3 months
El-Bagoory et al., 2021 [129]	Clinical trial	N/A	DSM 17938	When compared to only scaling and root planing, 6-month adjunctive treatment with L. reuteri DSM 17938 suspension (1 × 108 CFU) in patients with chronic periodontitis significantly reduces P. gingivalis load in the subgingival plaque (p < 0.05)
Mulla et al., 2021 [130]	In vitro	NA	unknown	L. reuteri can inhibit the growth of P. gingivalis isolated from the dental plaque (MIC = 25 mg/mL)
Lai et al., 2021 [49]	In vitro	ATCC 33277	17 strains	14 of 17 L. reuteri strains can inhibit the growth of P. gingivalis ATCC 33277
Yang et al., 2021 [131]	In vitro	BAA-308	AN417	L. reuteri AN417 culture supernatant can reduce the growth rate, viability and biofilm formation of P. gingivalis BAA-308 (minimal inhibitory volume: 10% (v/v))
Jansen et al., 2021 [132]	In vitro	ATCC 33277	ATCC PTA 5289	L. reuteri ATCC PTA 5289 with added glicerol significantly reduces the genome numbers of P. gingivalis ATCC 33277 (p < 0.01). This property disappears in the absence of glycerol
Widyarman et al., 2022 [117]	In vitro	ATCC 33277	N/A	Reuterin at a concentration of 12.5 μg/ml reduces P. gingivalis ATCC 33277 biofilm (p < 0.05) Reuterin at a concentration of 100 μg/ml is the most effective against P. gingivalis biofilm—reduces up to 50% of the biofilm
Widyarman et al., 2022 [133]	In vitro, model: HaCat cells	ATCC 33277	BEA 230424	Reuterin from L. reuteri BEA 230424 decreases the expression of IL8 and increases the expresion of human beta-defensin-2 by HaCat cells stimulated by P. gingivalis ATCC 33277
Widyarman et al., 2023 [134]	In vitro; ex vivo, model: root canal infection	ATCC 33277	LC 382 415	Reuterin from L. reuteri LC 382 415 can inhibit the growth of P. gingivalis ATCC 33277 (MIC = 12.5 µg/mL, MBC = 25 μg/mL) Reuterin at a concentration 100 µg/mL can effectively prevent the development of P. gingivalis biofilm in vitro and in ex vivo root canal infection model
Kim et al., 2023 [135]	In vitro, model: RAW 264.7 cells	NA	KCTC 3594	L. reuteri KCTC 3594 peptidoglycan (LrPGN) can inhibit the inflammatory response induced by P. gingivalis LPS
Van Holm et al., 2023 [84]	In vitro	ATCC 33277	V038	L. reuteri V038 cannot inhibit the growth of P. gingivalis ATCC 33277
			F471	L. reuteri F471 can inhibit the growth of P. gingivalis ATCC 33277 (inhibition ratio (± SD): 0.716 ± 0.242)
Van Holm et al., 2024 [87]	In vitro, model: human oral keratinocytes and THP-1 cells	ATCC 33277	9 strains	All assessed L. reuteri strains are effective against periodontal pathogens (including P. gingivalis ATCC 33277) and can produce reuterin (glycerol is necessary). Total reuterin production does not show significant correlation with the inhibition of P. gingivalis Eight L. reuteri strains reduce the prevalence of periodontal pathobionts (including P. gingivalis ATCC 33277) on the keratinocytes L. reuteri DSM 33633 cannot reduce the prevalence of pathobionts on the keratinocytes (including P. gingivalis ATCC 33277) Four L. reuteri strains significantly suppress IL-8 and TNF-alpha production and increase IL-10 production by THP-1 cells stimulated by P. gingivalis ATCC 33277-derived LPS
Mahdizade Ari et al., 2024 [51]	In vitro, model: HGFC	ATCC 33277	100	L. reuteri 100 can biofilms, aggregate and co-aggregate with P. gingivalis ATCC 33277 (co-aggregation rate: 46.1%) In the model using human gingival fibroblast cells, L. reuteri 100 introduced before P. gingivalis significantly reduces its ability to produce biofilm (HGFC model)

HaCat immortalized human keratinocyte cell line, MSC mesenchymal stem cells, RAW 264.7 murine macrophage cell line, THP-1 human leukemia monocytic cell line, GEC gingival epithelial cell, HGFC human gingival fibroblast cell, CFS cell-free supernatant, MIC minimum inhibitory concentration, MBC minimum bactericidal concentration, LPS lipopolysaccharide, IL-8 interleukin 8, IL-10 interleukin 10, TNF-alpha tumor necrosis factor-alpha, CFU colony-forming unit

Ligilactobacillus Salivarius

Ligilactobacillus salivarius (old name: Lactobacillus salivarius) is a Gram-positive, lactic acid bacterium that can be found naturally in the oropharyngeal-gastrointestinal tract of healthy humans [136]. It is capable of both parthenogenic heterotypic and homotypic fermentation [137]. L. salivarius is amongst the most important species in human saliva. It has various probiotic and health-promoting properties and has been generally recognized as safe (GRAS) status [138, 139]. L. salivarius is resistant to low pH and is able to efficiently colonize the host, improving the microflora composition [140]. Strains of L. salivarius produce organic acids, hydrogen peroxide, and bacteriocins, which are able to inhibit the growth and proliferation of pathogenic bacteria [141]. L. salivarius is able to regulate both oral and intestinal flora and create a microbial community with a domination of beneficial bacteria [138]. Strains of L. salivarius, like many other lactic acid bacteria, have an immunomodulatory potential influencing the production of cytokines [137]. Therefore, it can be used to improve the host’s immunity, limit the spread of infection, and prevent infections [142]. It is widely used both in the food industry and in medicine to treat chronic diseases such as cancer, colitis, and asthma [143]. Also, its role in the treatment of dental diseases was suggested [130].

In the case of L. salivarius, 22 studies were analyzed in the review: 10 in vitro studies and 2 clinical trials. A summary of studies available in the literature that concern the impact of L. salivarius strains on P. gingivalis is presented in Table 7.

Table 7.

The studies that concern the impact of Ligilactobacillus salivarius strains on Porphyromonas gingivalis

Authors, year	Type of study	P. gingivalis strain	L. salivarius strain	Results
Jang et al., 2016 [122]	In vitro	ATCC 33277	Unknown	L. salivarius can inhibit the growth of P. gingivalis ATCC 33277 (growth inhibition: > 95%) and reduces the production of hydrogen sulfide and methyl mercaptan by P. gingivalis
Higuchi et al., 2019 [144]	In vitro	ATCC 33277 and JCM 8525	WB21	When compared to the negative control, a filtrate of L. salivarius WB21 culture solution can inhibit the growth of P. gingivalis ATCC 33277 and JCM 8525 (p < 0.001)
Mousquer et al., 2020 [145]	In vitro	Unknown	G60	L. salivarius G60 can inhibit the growth of P. gingivalis after 72 h
Chen et al., 2020 [61]	In vitro	BCRC 17689, BCRC 17688	AP-32	Viable L. salivarius AP-32 has a strong antimicrobial activity against P. gingivalis BCRC 17689, BCRC 17688 (inhibition zone: 2–3 cm). Heat-killed L. salivarius AP-32 can inhibit the growth of P. gingivalis (inhibition rate: 80–100%)
Kucia et al., 2020 [136]	In vitro	ATCC 33277	SGL03	Salistat SGL03 (L. salivarius SGL03, lactoferrin, essential oils) has a bactericidal effect agains P. gingivalis ATCC 33277
Lin et al., 2021 [101]	In vitro	BCRC 17689 and BCRC 17688	AP-32	An oral lozenge containing viable L. salivarius subsp. salicinius AP-32, L. paracasei ET-66, L. plantarum LPL28 can inhibit the growth of P. gingivalis BCRC 17689 and BCRC 17688 (inhibition rate: 100%)
Lai et al., 2021 [49]	In vitro	ATCC 33277	78 strains	55 of 78 L. salivarius strains can inhibit the growth of P. gingivalis ATCC 33277
Mulla et al., 2021 [130]	In vitro	NA	unknown	L. salivarius can inhibit the growth of P. gingivalis isolated from the dental plaque (MIC = 50 mg/mL)
Lin et al., 2022 [111]	In vitro	BCRC 17689 and BCRC 17688	AP-32	An oral lozenge containing heat-killed L. salivarius subsp. salicinius AP-32 and L. paracasei ET-66 can significantly inhibit the growth of P. gingivalis BCRC 17689 and BCRC 17688 in vitro by 86.91% (p < 0.01) and 95.32% (p < 0.05), respectively
Sakata et al., 2023 [146]	Clinical trial	N/A	CP3365	When compared to placebo, 8-week treatment with tablets containing heat-killed L. salivarius CP3365 (4.4 × 109 cells) in healthy volunteers does not change the relative abundance of P. gingivalis in supragingival plaque and saliva
Zanetta et al., 2023 [147]	In vitro	DSM 20709	LS03	L. salivarius LS03 is very efficient in inhibiting biofilm formation and growth of P. gingivalis DSM 20709
Motta et al., 2024 [148]	Clinical trial	N/A	WB21	When compared to placebo, 2-week treatment with L. salivarius WB21 (6.7 × 108 CFU) capsules in young adults with a diagnosis of halitosis does not influence the amount of P. gingivalis on the dorsum of the tongue after 7, 14, and 30 days

N/A not applicable, MIC minimum inhibitory concentration, CFU colony-forming units

Lacticaseibacillus Paracasei

Lacticaseibacillus paracasei (old name: Lactobacillus paracasei) is a Gram-positive, heterofermentative lactic acid bacterium that is a part of the normal intestinal microbiota. It exhibits high levels of acid and bile tolerance and is resistant to lysozyme [149]. L. paracasei is characterized by antibiofilm and antimicrobial activity. It can stimulate the immune system, has anti-inflammatory properties, and can modulate the microbiota [150]. The beneficial properties of L. paracasei are associated with its presence and the production of effector molecules such as lactic acid, lactate, exopolysaccharides, and bacteriocins [150]. L. paracasei has demonstrated various beneficial effects in patients with digestive diseases, infections, depression, and obesity [151].

In the case of L. paracasei, 5 studies were analyzed in the review: 5 in vitro studies. A summary of studies available in the literature that concerns the impact of L. paracasei strains on P. gingivalis is presented in Table 8.

Table 8.

The studies that concern the impact of Lacticaseibacillus paracasei strains on Porphyromonas gingivalis

Authors, year	Type of study	P. gingivalis strain	L. paracasei strain	Results
Liu et al., 2018 [152]	In vitro	BCRC 14417	NTU-101	NTU101 FM (fermented skim milk produced using Lactobacillus paracasei subsp. paracasei NTU-101) ethanol extract can inhibit the growth of P. gingivalis BCRC 14417
Chen et al., 2020 [61]	In vitro	BCRC 17689, BCRC 17688	ET-66	Viable L. paracasei ET-66 has a strong antimicrobial activity against P. gingivalis BCRC 17689, BCRC 17688 (inhibition zone: ≥ 3 cm) Heat killed L. paracasei ET-66 can inhibit the growth of P. gingivalis (inhibition rate: 80–100%)
			GL-156	Viable L. paracasei GL-156 has a strong antimicrobial activity against P. gingivalis BCRC 17689, BCRC 17688 (inhibition zone: ≥ 3 cm). Heat-killed L. paracasei GL-156 can inhibit the growth of P. gingivalis (inhibition rate: 40–60%)
Lai et al., 2021 [49]	In vitro	ATCC 33277	44 strains	39 of 44 assessed strains of L. paracasei can inhibit the growth of P. gingivalis
			141	Among 308 assessed strains of lactic acid bacteria with an inhibitory effect on P. gingivalis, L. paracasei 141 has the greatest antimicrobial activity (inhibition zone (mean ± SE): 32.56 ± 0.84 mm)
Lin et al., 2022 [111]	In vitro	BCRC 17689, BCRC 17688	ET-66	Postbiotics of L. paracasei ET-66 can inhibit the growth of P. gingivalis BCRC 17689 and BCRC 17688
Thananimit et al., 2022 [83]	In vitro	ATCC 33277	SD1	Short-chain fatty acids of L. paracasei SD1 can inhibit the growth of P. gingivalis ATCC 33277 (inhibition zone (mean ± SD): 17.0 ± 0.4 mm; MIC (mean ± SD): 358.6 ± 0.0 µg/mL)

SD standard deviation, SE standard error, MIC minimum inhibitory concentration

Lactobacillus Gasseri

Lactobacillus gasseri is a Gram-positive, obligately homofermentative lactic acid bacterium. It is one of the most common strains of lactic acid bacteria that can be found in the human gastrointestinal and genital tracts [153]. It has the ability to inhibit some pathogenic bacteria and regulate the immune system [154]. L. gasseri produces gassericin A that can inhibit the growth of many pathogens [155]. L. gasseri has been defined as generally recognized as safe (GRAS) by the US Food and Drug Administration [156].

In the case of L. gasseri, 5 studies were analyzed in the review: 3 in vitro studies and 2 animal studies. A summary of studies available in the literature that concern the impact of L. gasseri strains on P. gingivalis is presented in Table 9.

Table 9.

The studies that concern the impact of Lactobacillus gasseri strains on Porphyromonas gingivalis

Authors, year	Type of study	P. gingivalis strain	L. gasseri strain	Results
Kobayashi et al., 2017 [157]	In vitro, model: THP-1 cells	381	N/A	β-defensin-14 inhibits the production of IL-1beta and TNF-alpha by THP-1 monocytes stimulated with P. gingivalis 381
	In vivo, model: mouse	381	SBT2055 (LG2055)	Oral administration of L. gasseri SBT2055 can control bone resorption and oral inflammation caused by P. gingivalis 381 infection (decrease of the TNF-alpha and IL6 levels, increase of mouse β-defensin-14 level)
Hirasawa et al.,. 2020 [94]	In vitro	FDC 381 and ATCC 33277	Unknown	1 strain of L. gasseri isolated from the saliva od periodontally healthy people can inhibit the growth of P. gingivalis FDC 381 and ATCC 33277 (inhibition zone > 12 mm)
Kobayashi et al., 2021 [158]	In vivo, animal model: mouse	JCM8525	O3-2	3-week treatment with L. gasseri O3-2 in mice infected with P. gingivalis JCM8525 reduces the alveolar bone loss and restores normal intestinal flora
Mann et al., 2021 [96]	In vitro	KCOM 2796	HHuMIN D	5% L. gasseri HHuMIN D supernatant can inhibit the growth of P. gingivalis KCOM 2796 (inhibition rate: 88 ± 1%) L. gasseri HHuMIN D can produce hydrogen peroxide, but does not co-aggregate with P. gingivalis KCOM 2796
Lai et al., 2021 [49]	In vitro	ATCC 33277	12 strains	7 of 12 L. gasseri strains can inhibit the growth of P. gingivalis ATCC 33277

THP-1 human leukemia monocytic cell line, TNF-alpha tumor necrosis factor-alpha, IL-1beta interleukin 1-beta, IL-6 interleukin 6

Other Lactobacillus Strains

In the case of other Lactobacillus strains, 5 studies were analyzed in the review: 12 in vitro studies (3 in vitro studies on cell lines), 3 animal studies, and 2 clinical trials. A summary of studies available in the literature that concern the impact of other Lactobacillus strains (Lacticaseibacillus casei, Lactobacillus delbrueckii, Lactiplantibacillus pentosus, Lactobacillus helveticus, Latilactobacillus curvatus , Lactobacillus crispatus, Limosilactobacillus mucosae, Latilactobacillus sakei) on P. gingivalis is presented in Table 10.

Table 10.

The studies that concern the impact of other Lactobacillus strains on Porphyromonas gingivalis

Authors, year	Type of study	P. gingivalis strain	Probiotic strain	Results
Lacticaseibacillus casei
Imran et al., 2015 [159]	Clinical trial	NA	L. casei Shirota	1-month daily consumption of a probiotic drink with L. casei Shirota in adult patients with mild/moderate periodontitis reduces P. gingivalis levels at 1-month and 2-month intervals
Hirasawa et al., 2020 [94]	In vitro	FDC 381 and ATCC 33277	L. casei, 3 strains	3 strains of L. casei isolated from the saliva of periodontally healthy people can inhibit the growth of P. gingivalis FDC 381 and ATCC 33277 (inhibition zone > 12 mm)
Lai et al., 2021 [49]	In vitro	ATCC 33277	L. casei, 43 strains	26 of 43 L. casei strains can inhibit the growth of P. gingivalis ATCC 33277
Albuquerque-Souza et al., 2021 [160]	In vitro, model: GEC	W83	L. casei 324 m	L. casei 324 m can enhance the re-epithelialization of gingival epithelial cells wounds and reverse/attenuate harmful effects of P. gingivalis W83
Lactobacillus delbrueckii
Cornacchione et al., 2019 [161]	In vitro	W83	L. delbrueckii STYM1, GVKM1, SYB7, SYB13	L. delbrueckii STYM1 and GVKM1 (but not SYB7 and SYB13) can inhibit the growth of P. gingivalis W83 L. delbrueckii STYM1 can produce hydrogen peroxide that can inhibit the growth of P. gingivalis
Michaylova et al., 2021 [79]	In vitro	DSM 20709	L. delbrueckii ssp. bulgaricus B1054, C3/2, LBB.B120, LBB.B130, 69/6P	Milk fermented with L. delbrueckii ssp. bulgaricus B1054, C3/2 and LBB.B120 (in contrast to strains LBB.B130 and 69/6P) can inhibit the growth of P. gingivalis DSM 20709. Freeze-dried preparations of these strains can inhibit the growth of P. gingivalis
Lai et al., 2021 [49]	In vitro	ATCC 33277	L. delbrueckii subsp. bulgaricus, 17 strains	13 of 17 Lactobacillus delbrueckii ssp. bulgaricus strains can inhibit the growth of P. gingivalis ATCC 33277
			L. delbrueckii subsp. lactis, 9 strains	8 of 9 Lactobacillus delbrueckii ssp. lactis strains can inhibit the growth of P. gingivalis ATCC 33277
Tennert et al., 2023 [162]	In vitro	ATCC 33277, Be-TR 4/5, Be-TR 602/9	L. delbrueckii ssp. bulgaricus, unknown	Lactobacillus delbrueckii ssp. bulgaricus can inhibit the growth of P. gingivalis ATCC 33277, Be-TR 4/5, Be-TR 602/9 (MIC, MBC ≤ 0.78%)
Lactiplantibacillus pentosus
Choi et al., 2021 [48]	In vitro	KCTC 5352	L. pentosus, unknown	L. pentosus can inhibit the growth of P. gingivalis KCTC 5352 (inhibition zone: 2.1 ± 0.2 mm)
Van Holm et al., 2023 [84]	In vitro	ATCC 33277	L. pentosus KCA1	L. pentosus KCA1 can inhibit the growth of P. gingivalis ATCC 33277 (inhibition ratio (± SD): 0.631 ± 0.058)
Ma et al., 2023 [163]	In vivo, animal model: mouse, experimental periodontitis	ATCC 33237	L. pentosus NK357	Oral administration of L. pentosus NK357 can alleviate periodontitis caused by P. gingivalis ATCC 33237 and systemic inflammation
Lactobacillus helveticus
Kobatake et al., 2019 [164]	In vitro, model: GEC	381 (JCM8525)	L. helveticus SBT2171 (LH2171)	L. helveticus SBT2171 (LH2171) upregulates the expression of beta-defensin in GECs, alleviates the inflammation in GECs stimulated by P. gingivalis 381 (JCM8525)
	In vivo, animal model: mouse, experimental periodontitis			L. helveticus LH2171 increases the expression of beta-defensin in the oral cavity and alleviates periodontal disease caused by P. gingivalis in mice
Chen et al., 2020 [61]	In vitro	BCRC 17689, BCRC 17688	L. helveticus RE-78	Viable L. helveticus RE-78 has a strong antimicrobial activity against P. gingivalis BCRC 17689, BCRC 17688 (inhibition zone: 2–3 cm). Heat killed L. helveticus RE-78 cannot inhibit the P. gingivalis growth
Lai et al., 2021 [49]	In vitro	ATCC 33277	L. helveticus, 42 strains	30 of 42 L. helveticus strains can inhibit the growth of P. gingivalis ATCC 33277
Latilactobacillus curvatus
Choi et al., 2021 [48]	In vitro	KCTC 5352	L. curvatus SMFM 2016-NK	L. curvatus SMFM2016-NK can inhibit the growth of P. gingivalis KCTC 5352 (inhibition zone: 1.0 ± 0.0 mm)
Jung et al., 2021 [165]	In vitro, model: HGFC	N/A	L. curvatus MG5246	L. curvatus MG5246 CFS has an anti-inflammatory effect on HGFCs stimulated by P. gingivalis derived LPS (decrease in the expression of PGE3, COX-2, MMPs, TNF-alpha, IL6, CXCL12, CXCL4, ICAM1)
	In vivo, animal model: rat, experimental periodontitis			8-week treatment with L. curvatus MG5246 (2 × 108 CFU/day) reduces alveolar bone loss in periodontitis (rat model)
Others: Lactobacillus crispatus, Limosilactobacillus mucosae, Latilactobacillus sakei
Tobita et al., 2018 [166]	Clinical trial	N/A	L. crispatus KT-11	When compared to the placebo group, 4-week treatment with L. crispatus KT-11 tablets (1.2 × 1010 cells) in healthy volunteers decreases the number of P. gingivalis in saliva
Li et al., 2023 [167]	In vitro	ATCC 3327	L. sakei MS103	L. sakei MS103 can auto-aggregate, co-aggregae with P. gingivalis ATCC 3327 and inhibit P. gingivalis biofilm formation
Van Holm et al., 2024 [87]	In vitro, model: human oral keratinocytes	ATCC 33277	L. mucosae DSM 33291	L. mucosae DSM 33291 cannot reduce the prevalence of pathobionts on the keratinocytes (including P. gingivalis ATCC 33277) L. mucosae DSM 33291 does not have any antimicrobial activity against P. gingivalis ATCC 33277

N/A not applicable, GEC gingival epithelial cell, HGFC human gingival fibroblast cell, SD standard deviation, MIC minimum inhibitory concentration, MBC minimum bactericidal concentration, LPS lipopolysaccharide, CFU colony-forming unit, PGE3 prostaglandin E3, COX-2 cyclooxygenase-2, MMP matrix metalloproteinase, TNF-alpha tumor necrosis factor-alpha, IL6 interleukin 6, CXCL12 C-X-C motif chemokine ligand 12, CXCL4 platelet factor 4 (PF4), ICAM1 intercellular adhesion molecule 1

Risk of Bias Assessment

The results of the risk of bias assessment were presented in Figs. 2, 3, 4, 5, 6, and 7.

Fig. 2.

Risk of Bias assessment of randomized controlled trials. For the evaluation, theRevised Cochrane risk-of-bias tool for randomized trials (RoB2) was used. D1, bias arising from the randomization process; D2, bias due to deviations from intended intervention; D3, bias due to missing outcome data; D4, bias in measurement of the outcome; D5, bias in selection of the reported results

Fig. 3.

Risk of Bias assessment of non-randomized study in humans. For the evaluation, the Risk Of Bias InNon-randomized Studies of Interventions (ROBINS-I) tool was used. D1, bias due to confounding; D2, bias due to selection of participants; D3, bias in classification of interventions; D4, bias due to deviations from intended interventions; D5, bias due to missing data; D6, bias in measurement of outcomes; D7, bias in selection of the reported results

Fig. 4.

Risk of biasassessment of animal trials. For the evaluation, the SYRCLE’s risk-of-bias tool for animal studies was used. D1, sequence generation; D2, baseline characteristics; D3, allocation concealment; D4, random housing; D5, blinding of caregivers; D6: random outcome assessment; D7, blinding of outcome assessment; D8, incomplete outcome data; D9, selective outcome reporting; D10, other bias

Fig. 5.

Risk of Bias assessment of in vitro studies. For the evaluation, the Quality Assessment Tool For In Vitro Studies (QUIN Tool) was used. D1, clearly stated objectives; D2, sample size calculation; D3, sampling technique; D4, details of comparison group; D5, explanation of methodology; D6, operator details; D7, randomization; D8, measurement of outcome; D9, outcome assessor details; D10, blinding; D11, presentation of results; D12, statistical analysis; D13, overall risk (%)

Fig. 6.

Risk of Bias assessment of in vitro studies using cell lines. For the evaluation, the Quality Assessment Tool For In Vitro Studies (QUIN Tool) was used. D1, clearly stated objectives; D2, sample size calculation; D3, sampling technique; D4, details of comparison group; D5, explanation of methodology; D6, operator details; D7, randomization; D8, measurement of outcome; D9, outcome assessor details; D10, blinding; D11, presentation of results; D12, statistical analysis; D13, overall risk (%)

Fig. 7.

Risk of bias assessment of in vitro studies. For the evaluation, the Quality Assessment Tool For In Vitro Studies (QUIN Tool) was used

Summary of Results

Seventy-two studies showed that various Lactobacillus strains are active against P. gingivalis. The following bacteria were included: L. brevis, L. acidophilus, L. rhamnosus, L. fermentum, L. plantarum, L. reuteri, L. salivarius, L. paracasei, L. gasseri, L. casei, L. delbrueckii, L. pentosus, L. helveticus, L. curvatus, L. crispatus, L. sakei, and L. mucosae. In in vitro studies, individual strains showed the following properties: (1) inhibition of P. gingivalis growth and biofilm formation, (2) auto-aggregation and co-aggregation with P. gingivalis, (3) alleviation of P. gingivalis LPS-induced inflammation, (4) reduction of P. gingivalis adhesion and invasion to gingival epithelial cells and maintenance of their viability, (5) protection of gingival epithelial cells affected by P. gingivalis, (6) influence on multi-species biofilms containing P. gingivalis, (7) influence on the immune response to P. gingivalis, (8) reduction of the prevalence of P. gingivalis on keratinocytes, (9) production of anti-microbial compounds active against P. gingivalis. In animal studies, individual strains were able to (1) decrease the oral load of P. gingivalis, (2) control bone resorption, elevate bone volume, and decrease bone porosity in experimental periodontitis, and (3) decrease inflammation in periodontal tissue from animals with experimental periodontitis. Lactobacillus strains evaluated in clinical trials were characterized by the ability to reduce P. gingivalis load in subgingival plaque, saliva, and crevicular fluid of both healthy volunteers and patients with chronic periodontal diseases. The studies emphasized that the above-presented features apply only to selected Lactobacillus strains and are strain specific; therefore, some Lactobacillus strains analyzed in the researches showed no effect on P. gingivalis.

Discussion

The literature review revealed a significant rise in publications on probiotic therapy and dental health, with most research originating within the past decade. Nonetheless, as a trending topic, probiotic therapy is a subject to a clear risk of publishing bias. This is evidenced by the predominance of favorable findings in the conclusions and the near equivalence of subjective or narrative reviews to original investigations. Additionally, the studies reviewed vary widely in terms of methodology and strains tested, making interpretation, and especially comparison, challenging.

This review sought to address the question of whether lactobacilli with probiotic properties can affect P. gingivalis, a major factor in periodontal diseases. To the best of our knowledge, our study is the first to examine this particular topic in detail. Contrary to other researchers, we wanted to present the results of both in vitro and in vivo studies, including clinical trials and animal models. Considering the small number of clinical trials that assess the effect of lactobacilli with probiotic properties on periodontal diseases and even fewer studies including microbiological aspects related to P. gingivalis, in vitro studies seem crucial for future researchers to expand knowledge in this field.

The findings of this review align with the current understanding that strain selection is crucial, as different strains of the same species may exhibit completely distinct properties [161]. Probiotics are highly strain-specific and disease-specific; therefore, the clinical choice is challenging [168]. In vitro studies have indicated that among tested potential probiotic strains, the properties and effectiveness differ from strain to strain. Analyzing the literature, we have found that various lactobacilli have an antimicrobial activity against P. gingivalis [47–49, 58, 61, 78–80, 83–85, 87, 94, 96, 97, 101, 108, 111, 122, 130, 134, 144, 145, 152, 161, 162]. However, within a given species, some strains can inhibit P. gingivalis growth, while others lack this ability. The inhibitory effects of different strains are quantified using the inhibition zone in the Agar Diffusion Test. Contradictory results have also been observed, particularly in studies of L. rhamnosus GG, where some studies report inhibition of P. gingivalis growth, while others do not. Today, the use of strain designations in research is recommended to accurately determine the strain-specific efficacy [169]. However, this guideline is not always followed.

We found that the ability of lactobacilli strains to auto-aggregate and co-aggregate with P. gingivalis has been frequently highlighted [24, 47, 51, 96]. Probiotics need to possess the ability to auto-aggregate to achieve the required cell mass, which is essential for exerting beneficial effects and enhancing their activity [24]. The ability of probiotics to co-aggregate with other microorganisms is also important for the development and maintenance of biofilm communities, particularly in the oral environment [24]. Co-aggregation with pathogenic strains prevents the pathogen’s adhesion, eliminates already adhering pathogens, and replaces them with probiotic bacteria [170]. It is crucial to form a barrier inhibiting further pathogenic bacterial colonization [171]. Several in vitro studies have shown that lactobacilli strains can change the abundance of P. gingivalis in multi-species biofilms and reduce the ability of P. gingivalis to produce biofilms [47, 51, 62, 101, 105, 109, 110, 117, 131, 134, 147, 167]. These properties are important in the context of periodontal diseases, as biofilm is the primary etiological factor in their initiation and progression [172].

The analysis has shown that various Lactobacillus strains are able to produce compounds with antimicrobial properties. Short-chain fatty acids of L. rhamnosus strains and L. paracasei SD1, a dipeptide of L. fermentum ALAL020, plantarcin 149 from L. plantarum NRIC 149, exopolysaccharides from L. plantarum EIR/IF-1, and a bacteriocin from L. plantarum NC8 have inhibited the growth of P. gingivalis in vitro [83, 97, 101, 108, 110].

Special attention in the literature is given to reuterin produced by L. reuteri for its antibacterial properties, as this compound can inhibit both the growth of P. gingivalis and its biofilm formation. Additionally, reuterin has anti-inflammatory properties, promotes wound healing, and neutralizes LPS produced by P. gingivalis [117, 123, 126]. Two in vitro studies have evaluated the effects of L. reuteri ATCC-55730 and reuterin from L. reuteri BEA 230424 on the production of human-β-defensin-2 by HaCat cells exposed to P. gingivalis [117, 123]. The study from 2018 has shown that L. reuteri supplemented with glycerol reduces the expression of human-beta-defensin-2 as well as the expression of IL-8 on HaCat cells. L. reuteri requires glycerol to produce reuterin with anti-inflammatory properties, capable of inhibiting pathogenic oral bacteria and acting [123]. Conversely, the 2022 study reported the opposite effect on the production of human-β-defensin-2 on HaCat cells with a similar effect on IL-8 expression [117]. The inconsistent results between these studies may indicate potential methodological differences or variations in experimental conditions, which could account for the differing outcomes. β-defensins are active against Gram-negative and Gram-positive bacteria and play a crucial role in the immune response against pathogenic bacteria in gingival tissues [173]. β-defensins are implicated in periodontal diseases, and their functions are complex, showing both pro- and anti-inflammatory properties. In vitro human β-defensins are generally induced in response to microbial pathogens in buccal and gingival epithelial cells [174]. Several in vitro studies have shown that probiotics induce antimicrobial beta-defensins [175]. Upregulation of β-defensin levels has also been demonstrated in three animal studies assessing the impact of L. gasseri, L. pentosus, and L. helveticus strains on the inflammation caused by P. gingivalis in mice [157, 163, 164].

Additionally, some lactobacilli (L. brevis, L. fermentum, L. gasseri, L. delbrueckii) have been shown to produce hydrogen peroxide [43, 96, 161]. Strictly anaerobic bacteria such as P. gingivalis are adapted to grow in the absence of free oxygen and in reduced conditions. Oxidizing agents, such as hydrogen peroxide, inhibit the growth of P. gingivalis and negatively influence its biological properties [176].

The ability of probiotics to produce organic acids contributes to their antimicrobial activity by activation of bacteriocin-like compounds in acidic conditions or through the direct antagonistic effects of the acids [177]. Organic acids can rupture and neutralize bacterial cells’ cytoplasmic membrane, interfere with biofilm formation by influencing the quorum sensing of bacteria [178, 179]. However, the acid production should not be influenced by sugar supplementation, as it may lead to dental caries [180]. In fact, lactobacilli are considered cariogenic, as lactic acid produced by them is able to weaken the enamel. It is generally believed that strains producing excessive amounts of organic acids should be avoided, while probiotics that are weak lactic acid producers may be more suitable for oral application [43, 44]

The analysis has shown that certain Lactobacillus strains can modify the immune response, as demonstrated in several studies [24, 46, 59, 80–82, 87, 112, 135, 165]. These properties are important because P. gingivalis activate inflammatory responses in affected periodontium [181]. The ability of probiotics to modulate the immune response leads to a reduction of inflammation and tissue destruction. They are known to be able to enhance the host immune responses (for example IgA production), inhibit the production of pro-inflammatory cytokines induced by pathogens, and decrease the production of matrix metalloproteinases [33]. Various Lactobacillus species exhibit these properties. Certain strains or their products (including L. brevis, L. rhamnosus, L. plantarum, L. reuteri, L. curvatus, L. helveticus) can inhibit inflammatory responses in cells activated by P. gingivalis by decreasing pro-inflammatory cytokine levels and increasing anti-inflammatory cytokine ones [46, 81, 82, 87, 112, 135, 165].

However, research findings are sometimes contradictory for certain species. For instance, three studies indicate that L. rhamnosus strains (T7, GG, MG4706, MG4709, MG4711) alleviate inflammation caused by P. gingivalis by reducing pro-inflammatory molecule production [81, 82, 87]. Furthermore, three other studies show that L. rhamnosus strains (Lr-32, ATCC9595) upregulate the transcription of inflammatory mediators, such as CXCL8, thereby increasing the immune system’s recognition of P. gingivalis [24, 59, 80]. The effect of L. rhamnosus on the immune system appears complex and sometimes inconsistent. While most studies suggest immunomodulatory functions, a certain number of studies have explored its immunostimulatory potential [63]. A possible dual role of L. rhamnosus strains in maintaining immune homeostasis has been suggested [182]. The strain-specific nature of probiotics’ effects on immune functions has been highlighted in previous studies. The impact on the immune function depends clearly on the probiotic strain and immune parameters assessed [183]. In this case, more research is needed to explain this phenomenon. It would be valuable to include different strains of L. rhamnosus and different parameters of the immune system. Moreover, it would be important to characterize these strains, determine in detail their effect on the immune system and the mechanisms that underlie it. Then, testing these strains in vivo would allow us to know their actual action in the human body.

Bacterial colonization of soft tissue structures is crucial for the pathogenesis of periodontal disease [184]. P. gingivalis has an ability to invade gingival epithelial cells and induce apoptosis [184, 185]. It possesses various virulence factors, such as fimbriae, lipopolysaccharide, capsule, proteases, and hemagglutinins, potentially significant in the pathogenesis of periodontal disease [184]. Several in vitro studies on cell lines have demonstrated that Lactobacillus strains can interfere with the invasion process of P. gingivalis. Various strains reduce P. gingivalis prevalence on cells and inhibit its adhesion and invasion. They can maintain cell viability, protect the proliferation of cells affected by P. gingivalis, reduce its proapoptotic effect, and enhance the re-epithelialization [59, 60, 87, 160].

Our analysis shows that despite numerous in vitro studies with promising results, clinical studies evaluating the effects of probiotic therapy on P. gingivalis are limited, and their results are ambiguous. Nine clinical trials have demonstrated promising results with probiotic therapy using strains of L. crispatus, L. casei, L. reuteri, L. rhamnosus, L. brevis, and L. plantarum. Therapy with these probiotics has led to a significant reduction in the amount of P. gingivalis in dental plaque compared to placebo [50, 76, 86, 124, 127–129, 159, 166]. Consequently, three clinical studies found that strains of L. salivarius and L. rhamnosus had no effect on the P. gingivalis abundance [75, 146, 148]. Once again, the strain specificity of probiotics needs to be carefully considered. It is essential to keep in mind that these studies involved various bacterial strains. Analyzing and comparing the results of these clinical trials is challenging not only due to the variety of strains used but also due to the diverse patient profiles. The studies were conducted both in healthy volunteers and in patients with various characteristics including adults and children, individuals with different oral diseases (e.g., periodontitis, mucosistis, peri-implantitis, halitosis), and patients with comorbidities (type 2 diabetes, intellectual disability). The results of the clinical trials provide some insight into the possibility of using probiotics in oral diseases associated with P. gingivalis. However, before this type of practice can be widely adopted, it is necessary to conduct extensive, multicenter, randomized placebo-controlled clinical trials with well-characterized strains and carefully selected patient groups.

From a clinical point of view, the use of probiotics is suggested in chronic periodontitis patients as an adjunctive therapy to scaling and root planning. It can improve their clinical outcome and reduce periodontitis pathogens level [192]. Their effectiveness as an additional therapy to mechanical plaque management techniques was assessed compared to traditional antimicrobial agents such as chlorhexidine. This is particularly important due to the side effects associated with the use of this substance. According to Soares et al., probiotics may be an alternative to chlorhexidine in enhancing periodontal health; however, more high-quality studies are needed to assess the clinical use of probiotics. They should be focused on, among others, the selection of the most appropriate strains of probiotics, their concentration, and the method of application [193]. According to clinical observations, the regular use of probiotics can also be used in the prevention of periodontal disease. By increasing the amount of beneficial bacteria and hindering the growth of pathogenic species, such as P. gingivalis, they can minimize the risk of development of periodontal diseases [194]. However, probiotic therapy is still a novel concept in dentistry. Therefore, to recommend their use at a clinical level, some questions need to be answered. Aspects such as selection of the appropriate strain, dose, and frequency of probiotic use, as well as the method of administration require detailed examination [195]. Our analysis showed that there were significant differences between the studies in the following aspects: probiotics used (L. reuteri, L. rhamnosus, L. brevis, L. plantarum, L. casei, L. crispatus), frequency of administration (from once to twice daily), doses (from 2 × 10⁷ to 6 × 10⁹ CFU/day), duration of the treatment (from 3 weeks to 6 months) and mode of application (tablets, suspension, lozenge, gel, yogurt). The appropriate strain, dose, and frequency of administration are extremely important to ensure effectiveness and safety of use. Moreover, in order to prevent or treat oral diseases, probiotics have to be administered in specific ways which ensure their gradual release. Specially designed formulas, applications, and devices such as lozenges, toothpastes, chewable tablets, mouthwashes, mousses, chewing gums, and local delivery have been proposed [186, 196]. The results we have obtained clearly indicate the need to expand knowledge on the use of probiotics in the fight against periodontal diseases before such methods of treatment and prevention can be widely used.

Conclusions and Future Aspects

This review has shown that various therapeutic advantages of Lactobacillus strains in relation to P. gingivalis have been demonstrated in both in vitro and in vivo studies. It seems that probiotics may find application in the treatment of periodontal diseases, as well as in their prevention. By using them in the healthy population, it may be possible to minimize the risk of development of periodontal diseases and the burden of disease. Although promising results have been observed, the studies analyzed here can only be a prelude to further research. Various Lactobacillus strains have the potential to promote oral health, but to thoroughly understand their effect, each strain should be evaluated separately in numerous, reliable studies. Future research is needed to fully understand the long-term effects of probiotic bacteria in the oral cavity and their ability to control P. gingivalis.

What Is Novelty?

In this review, we tried to answer the question of whether lactobacilli with probiotic properties can affect P. gingivalis, a major etiologic factor in periodontal diseases, and summarize the current knowledge on this topic. Despite numerous papers published over the last years, we found points that were still worth expanding. We focused on analyzing the influence of a specific group of bacteria—lactobacilli, on a specific aspect of periodontal disease—P. gingivalis, and analyzed the influence of as many as seventeen species of Lactobacillus. We summarized the results not only of clinical trials using probiotics as an adjunctive therapy to periodontal therapy but also of in vitro and in vivo studies (including animal models) addressing the effects of lactobacilli on P. gingivalis. In our review, we focused on a detailed analysis of microbiological aspects that are often omitted in clinical studies.

Limitations

The studies presented above highlight the potential use of selected Lactobacillus strains in managing oral diseases associated with P. gingivalis. Many strains are capable of inhibiting the growth of P. gingivalis and positively affecting cells infected with this pathogen. However, these results obtained in in vitro studies require verification in in vivo studies and clinical trials. Also, some strains show the desired effects in clinical trials, but these studies are relatively few and cover a small number of strains. Therefore, additional in vivo experimental models and clinical studies should be conducted to provide stronger evidence for the potential of Lactobacillus strains to control P. gingivalis in the context of oral cavity diseases.

It is important to note that the above analyzed studies include different bacterial strains (of both lactobacilli and P. gingivalis) or even the same strains but assessed in different conditions. Moreover, the presented studies differ significantly in their methodology. These elements can have a significant impact on their results and the extent to which they are useful in clinical practice. What is more, in several studies, the probiotic strains, especially those isolated from patients, were not described in detail. In order to explain their interaction with P. gingivalis and the potential inhibitory effect against this pathogen, further examination of their composition and released products is necessary.

Special attention should also be paid to the safety of the probiotics. Issues such as antibiotic resistance, invasive infections, probiotic-drug compatibility, vulnerable populations, long-term colonization, probiotic quality, and adverse events must be taken into consideration.

Conclusions

It appears that a significant proportion of Lactobacillus strains may possess probiotic properties and positively affect P. gingivalis. However, detailed in vivo experimental models and clinical studies are necessary to verify in vitro findings, assess their actual effect on P. gingivalis in the human oral cavity, as well as make sure of their safety.

Author Contribution

All authors contributed to the study conception and design. Material preparation and data collection was performed by C.K., J.N., T.M.T. and K.K.. The first draft of the manuscript was written by A.K. and edited by T.S. and M.K.. Authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Data Availability

No datasets were generated or analysed during the current study.

Declarations

Ethics Approval

This was a review study; no ethical approval was required.

Competing Interests

All authors declare no financial or non-financial competing interests.