Abstract
Purpose
Osteoradionecrosis (ORN) and medication-related osteonecrosis of the jaw (MRONJ) are relatively rare and refractory, and there is no consensus regarding the bacteria associated with their development. This study was conducted to identify the bacteria associated with refractory ORN and MRONJ, including severe cases.
Methods
Patients who underwent surgery for osteonecrosis of the jaw were included in this study. Bacterial culture specimens were obtained from tissue as deeply as possible. Severe cases of ORN and MRONJ were defined as stage IV of Lyon’s classification and stage III of the AAOMS classification, respectively. Demographic data, clinical features, antimicrobials usage, and bacteria detected were analysed to determine the factors associated with severe disease.
Results
Seventy-seven patients (ORN, n = 22; MRONJ, n = 55) were analysed. Penicillins were the most commonly used antimicrobials. A total of 311 bacterial strains were detected in tissue culture (detection rate = 100%). Streptococcus spp. were the most common bacteria (37.0%), followed by anaerobes (33.8%). Gram-negative rods were detected in 10.3% of the patients, antimicrobial-resistant bacteria in 78.4%, and ampicillin resistance in 60.8%. Factors associated with severe disease were ampicillin resistance and malignancy in MRONJ, with odds ratios of 8.74 (95% confidence interval, 1.20–63.4; p = 0.032) and 13.5 (1.09–168, p = 0.043), respectively. Enterobacter spp. were detected only in severe cases.
Conclusion
Bacteria associated with osteonecrosis of the jaw are similar in composition to those responsible for common odontogenic infections, but with a higher proportion of gram-negative rods. Ampicillin-resistant bacteria, including Enterobacter spp., are implicated in severe disease.
Supplementary Information
The online version contains supplementary material available at 10.1007/s00784-025-06547-3.
Keywords: Osteoradionecrosis of the jaw, Medication-related osteonecrosis of the jaw, Microorganism, Antimicrobial resistance, Gram-negative rod, Ampicillin
Introduction
Osteonecrosis of the jaw typically follows a chronic course and is often refractory to treatment, especially when managed conservatively. Osteoradionecrosis (ORN) and medication-related osteonecrosis of the jaw (MRONJ) are types of osteonecrosis that affect the jaw; however, neither occurs with high frequency, with their reported prevalence rates ranging from 5.4 to 13.2% [1] and 0.58 to 7.21% [2], respectively. The most current accepted mechanism for the pathogenesis of ORN is radiation-induced fibrosis of the tissue; that is, the radiation-induced fibroatrophic theory [3]. MRONJ is believed to be caused by the inhibition of bone remodelling through the suppression of osteoclasts [4]; however, the exact mechanism underlying its development remains unclear. Although the pathogeneses of ORN and MRONJ are believed to be different, they have similar clinical and histological features [5, 6] and are both refractory to antibacterial treatment.
Some studies have indicated that Actinomyces spp [7]. and common odontogenic infection-causing organisms are involved in the development of osteonecrosis of the jaw [8]. However, the methods used for specimen analysis in these studies were not consistent; some samples were assessed histopathologically [7], some were collected using swabs [9], and some were collected from tissues [10]. Collection of samples from the mouth for identification of causative organisms is associated with a high risk of contamination owing to the presence of indigenous bacteria in the oral cavity. Therefore, the optimal methods for collection of specimens from the oral cavity remain controversial. Notably, although there have been reports on specimen collection from the oral cavity in otolaryngology cases [11], no case of such specimen collection for oral maxillofacial surgery has been reported.
Narrow-range penicillins are the first choice antimicrobials for odontogenic infections. Clindamycin (CLDM) is also commonly used for the treatment of odontogenic infections [12]. However, β-lactamase-producing and CLDM-resistant bacteria have been frequently detected in osteonecrosis of the jaw [13, 14]. Moreover, osteonecrosis of the jaw may require frequent or long-term antimicrobial treatment [15], and information on the target bacteria is essential for effective empirical therapy. However, there is no consensus on the bacterial species associated with osteonecrosis of the jaw.
Factors that contribute to the severity of osteonecrosis of the jaw include age, hypoalbuminaemia, amount of exposure, and diabetes mellitus [16–19]. However, no study has been conducted to analyse the association between the causative organism and severity of osteonecrosis of the jaw. Therefore, the aim of this study was to analyse bacteria in tissue samples from patients with osteonecrosis of the jaw and determine the association between the severity of osteonecrosis of the jaw and the identified bacteria species, including resistant bacteria.
Materials and methods
Study design and patients
This was a retrospective case-control study of patients who underwent surgery for ORN or MRONJ at the Department of Oral and Maxillofacial Surgery, Kobe University Hospital between January 2016 and December 2023.
ORN was defined according to the Common Terminology Criteria for Adverse Events v5.0 (CTCAE ver. 5) [20]. The diagnostic criteria for ORN were devitalisation and exposure of bone through the overlying mucosa within the irradiated area (grade ≥ 2, CTCAE ver. 5) that persisted without healing for three months in the absence of tumour recurrence [21, 22]. MRONJ was diagnosed based on the following diagnostic criteria proposed by the American Association of Oral and Maxillofacial Surgeons (AAOMS) [23]: (1) previous or current treatment with anti-resorptive agents (ARAs) alone or in combination with immunomodulatory or angiogenesis inhibitors, (2) bone exposed through an intraoral or extraoral fistula in the maxillofacial region lasting for more than 8 weeks or capable of exploration, and (3) no history of radiation therapy to the jaws or disease metastasis to the jaws. The inclusion criterion was tissue culture of surgical specimens.
Specimens were collected from the deepest part of the lesion. In addition, the specimens were collected from multiple tissues (necrotic bone, granulation tissue, periosteal reaction, and pus) if possible. Pus samples were collected using sampling swabs. The tissues were stored in sterile spits filled with saline solution immediately after collection. Samples from different types of tissues were stored separately. The exclusion criteria were missing laboratory data and unavailable data on antimicrobial usage.
Data collection
Patient medical data were extracted from electronic medical records. The data collated for analysis included patient characteristics (age, sex, body mass index, smoking and drinking history, immunocompromised status [diabetes mellitus, corticosteroid usage], cancer-bearing status), data on haematological examination performed just before surgery (albumin [g/dL], haemoglobin [g/dL], estimated glomerular filtration rate [mL/min/1.73 m2], white blood cell count [/µL] and its fractions [number of neutrophils and lymphocytes]), osteonecrosis characteristics (site [maxilla, mandible], type of osteonecrosis [ORN, MRONJ], stage classification, history of cellulitis), the period from diagnosis of osteonecrosis of the jaw to surgery, presence and frequency of antimicrobial use before surgery, duration of antimicrobial use (oral, intravenous) before surgery, and bacteria detected in tissue culture. For patients with MRONJ, we also investigated whether ARAs were administered for osteoporosis or malignancy.
The severity of ORN was categorised according to Lyon’s classification [24]: stage I, affected (damaged or exposed) bone < 2.5 cm; stage II, affected bone > 2.5 cm, asymptomatic; stage III, affected bone > 2.5 cm, symptomatic; and stage IV, affected bone with pathological fracture, orocutaneous fistula, or involvement of the inferior alveolar nerve. The severity of MRONJ was categorised using the AAOMS stage classification [23]: stage I, exposed and necrotic bone or fistula that probes to the bone in patients who are asymptomatic and have no evidence of infection/inflammation; stage II, exposed and necrotic bone or fistula that probes to the bone, with evidence of infection/inflammation; and stage III, exposed and necrotic bone or fistulae that probe to the bone, with evidence of infection, and one or more of the following: exposed necrotic bone extending beyond the region of alveolar bone (i.e., inferior border and ramus in the mandible, maxillary sinus, and zygoma in the maxilla), pathologic fracture, extraoral fistula, oral antral/oral-nasal communication, and osteolysis extending to the inferior border of the mandible or sinus floor. Severe cases were defined as stage IV for ORN and stage III for MRONJ.
Our institution has been accredited to ISO 15,189 (certification number, RML00980), with standard operating procedures established and implemented for all inspection processes. Following the methods outlined in a previous report [25], antimicrobial susceptibility testing was performed using microbiological laboratory records according to the Clinical and Laboratory Standards Institute recommendations.
Endpoints
The primary endpoint was confirmation of the relationship between the severity of osteonecrosis of the jaw and bacterial species, including resistant bacteria. The secondary endpoint was identification of the bacteria associated with osteonecrosis of the jaw and confirmation of potential differences in the bacteria associated with ORN and MRONJ. The third endpoint was identification of other factors associated with the severity of osteonecrosis of the jaw.
Statistical analysis
Representative values are presented as medians with the first and third quartiles. Fisher’s exact test was used for comparisons of nominal variables across disease stages. The Brunner–Munzel test was used for two-group comparisons of continuous variables. The variables associated with disease severity in the univariate analysis were included in a multivariate logistic regression model. All statistical analyses were performed using the R software version 4.1.0 (R Development Core Team, 2021; R Foundation for Statistical Computing, Austria). The significance level was set at p < 0.05.
Results
Patient and osteonecrosis characteristics
Of 84 patients who were diagnosed with ORN or MRONJ and underwent surgical treatment, 77 patients met the inclusion criteria and seven were excluded (Fig. 1). Of the 77 patients, 22 had ORN and 55 had MRONJ. Approximately half of the patients were immunosuppressed. Osteonecrosis of the jaw occurred in the mandible in most cases. All the 22 patients with ORN (28.6%) received radiation therapy of 60 Gy or higher (local radiation dose unknown). Of the 55 patients with MRONJ (71.4%), 33 developed the disease due to use of osteoporosis medications, whereas 22 developed the disease due to treatment for malignant tumours. Of the 77 patients in the entire cohort, 36 (46.8%) had severe disease. In addition, approximately half of the patients had a history of cellulitis. The median period from diagnosis of osteonecrosis of the jaw to surgery was 136 days. Most of the patients were treated with antimicrobials, which were administrated intravenously in half of the cases (Table 1).
Fig. 1.
Flowchart of data collection and cleaning MRONJ, medication-related osteonecrosis of the jaw; ORN, osteoradionecrosis of the jaw
Table 1.
Characteristics of the patients
| Variables | Number of patients (n = 77) |
|---|---|
| Patient characteristics | |
| Age (years) | 73 (68, 82) |
| Sex (male) | 27 (35.1%) |
| Body mass index | 20.9 (19.1, 23.4) |
| History of smoking | 15 (19.5%) |
| Alcohol consumption | 20 (26.0%) |
| Immunocompromise | 43 (55.8%) |
| Cancer-bearing | 23 (29.9%) |
| Haematologic examination | |
| Albumin (g/dL) | 3.8 (1.6, 4.9) |
| Haemoglobin (g/dL) | 11.6 (6.3, 15.6) |
| eGFR (mL/min/1.73m2) | 59.9 (46.6, 72.3) |
| White blood cell (/µL) | 6250 (2400, 14400) |
| Neutrophil (%) | 66 (25, 92) |
| Cell count | 4019 (2989, 5398) |
| Lymphocyte (%) | 23 (3, 54) |
| Cell count | 1402 (903, 1818) |
| Osteonecrosis characteristics | |
| Location | |
| Maxilla | 13 (16.9%) |
| Mandible | 64 (83.1%) |
| Type of osteonecrosis | |
| ORN | 22 (28.6%) |
| MRONJ | 55 (71.4%) |
| Underlying osteoporosis | 33 (60.0%) |
| Underlying malignancy | 22 (40.0%) |
| ORN stage | |
| Stage III | 5 (22.7%) |
| Stage IV | 17 (77.3%) |
| MRONJ stage | |
| Stage II | 36 (65.5%) |
| Stage III | 19 (34.5%) |
| Severe condition | 36 (46.8%) |
| Cellulitis | 38 (49.4%) |
| Duration from diagnosis to surgery (days) | 136 (61, 441) |
| Use of antimicrobials before surgery | 68 (88.3%) |
| Intravenous administration | 34 (44.2%) |
Data are presented as median (first quartile, third quartile) or n (%)
Characteristics of antimicrobials
Antimicrobials were administered during the acute inflammatory phase and continued when symptoms persisted, even after objective signs of inflammation had disappeared. The penicillin-based antimicrobials were mostly administered orally, especially amoxicillin with clavulanic acid (CVA/AMPC), a beta-lactamase inhibitor (Fig. 2A). Sulbactum/ampicillin (SBT/ABPC), a combination penicillin-derived beta-lactamase inhibitor, was the most commonly used injectable drug, followed by ceftriaxon, a third-generation cephem antibacterial (Fig. 2B). Regarding duration of use, the median duration of use per dose was more than one month for oral macrolides (roxithromycine, RXM; clarithromycine, CAM) (Fig. 2C). SBT/ABPC was the most commonly administered intravenous antimicrobial, with a median duration of use of 6 days per dose (Fig. 2D).
Fig. 2.
Types and quantity of antimicrobials used before surgery (A) Usage rate for oral antimicrobials. (B) Usage rate for intravenous antimicrobials. (C) Duration of use (number of days) for each oral antimicrobial. (D) Duration of use (number of days) for each intravenous antimicrobial
AMPC, amoxicillin; AZM, azithromycine; CAM, clarithromycine; CEZ, cefazorin; CLDM, clindamycine; CMZ, cefmetazole; CTRX, ceftriaxon; CVA/AMPC, clavulanic acid/amoxicillin; LVFX, levofloxacin; RXM, roxithromycine; SBT/ABPC, sulbactam/ampicillin; STFX, sitafloxacine
Bacteria detected in tissue culture
The bacterial detection rate in this study was 100%. Multiple tissue samples were collected from 39 patients (50%), and the bacteria detected in the multiple tissues were consistent for 31 patients (80%). A total of 311 bacterial strains were detected in the tissue cultures. Gram-positive cocci were the most common, accounting for 145 strains (46.6%), 78% of which were Streptococcus spp. (particularly S. anginosus). A total of 105 strains (33.8%) of obligate anaerobes were detected, 37% of which were Prevotella spp. Five strains of Candida spp. were detected. Actinomyces spp. were detected less frequently, with only seven isolates identified (2.3%). Notably, the composition of the bacteria detected in this study was similar to that previously reported for bacteria detected in abscesses [26]; however, a higher proportion of gram-negative rods was detected in this study (Fig. 3A; Table 2). Regarding types of osteonecrosis, the composition of bacteria detected in patients with ORN and MRONJ was almost the same; however, a higher proportion of gram-negative rods was detected in patients with ORN (Fig. 3B). There was no significant difference in the period from diagnosis of osteonecrosis of the jaw to surgery in cases where obligate anaerobes were detected (p = 0.992). In contrast, cases in which Gram-negative rods were detected had a significantly longer period from diagnosis of osteonecrosis to surgery (p = 0.037), as well as a longer duration of antimicrobial use (median 55 days vs. 18 days, p = 0.025).
Fig. 3.
Bacterial species detected in tissue cultures (A) Comparison of bacteria species detected with common odontogenic infection-causing bacteria. As a reference, bacteria detected in abscesses caused by odontogenic infections other than osteomyelitis were shown (partly modified from Ref. 26). Among the gram-positive cocci, Streptococcus spp. were detected in 37.3%. (B) Percentage of bacteria detected in specimens from patients with ORN and MRONJ
MRONJ, medication-related osteonecrosis of the jaw; ORN, osteoradionecrosis of the jaw
Table 2.
Bacteria detection rate categorised according to type of osteonecrosis
| GPC | No. (%) | GPR | No. (%) | GNC | No. (%) | GNR | No. (%) | Obligate anaerobe | No. (%) | |
|---|---|---|---|---|---|---|---|---|---|---|
| [ORN] | ||||||||||
|
Stage III (N = 12) |
Streptococcus spp. | 6 (50%) | Lactobacillus spp. | 1 (8.3%) | Neisseria spp. | 1 (8.3%) | Prevotella spp. | 1 (8.3%) | ||
| Bacillus spp. | 1 (8.3%) | Others | 2 (16.7%) | |||||||
|
Stage IV (N = 66) |
Streptococcus spp. | 21 (31.8%) | Actinomyces spp. | 1 (1.5%) | - | Enterobacter spp. | 5 (7.6%) | Prevotella spp. | 9 (13.6%) | |
| Staphylococcus spp. | 5 (7.6%) | Lactobacillus spp. | 1 (1.5%) | Klebsiella spp. | 2 (2.8%) | Parvimonas micra | 2 (3.0%) | |||
| Enterococcus spp. | 1 (1.5%) | Corynebacterium spp. | 1 (1.5%) | Escherichia coli | 1 (1.5%) | Fusobacterium spp. | 2 (3.0%) | |||
| Gemella spp. | 1 (1.5%) | Pseudomonas spp. | 1 (1.5%) | Bacteroides spp. | 1 (1.5%) | |||||
| Others | 4 (6.1%) | Others | 8 (12.1%) | |||||||
| [MRONJ] | ||||||||||
|
Stage II (N = 144) |
Streptococcus spp. | 57 (39.6%) | Actinomyces spp. | 5 (3.5%) | Neisseria spp. | 3 (2.1%) | Eikenella spp. | 4 (2.8%) | Prevotella spp. | 17 (11.7%) |
| Staphylococcus spp. | 7 (4.9%) | Bacillus spp. | 2 (1.4%) | Klebsiella spp. | 2 (1.4%) | Parvimonas micra | 8 (5.6%) | |||
| Granulicatella spp. | 2 (1.4%) | Corynebacterium spp. | 1 (0.7%) | Escherichia coli | 1 (0.7%) | Fusobacterium spp. | 6 (4.2%) | |||
| Enterococcus spp. | 1 (0.7%) | Citrobacter spp. | 1 (0.7%) | Bacteroides spp. | 2 (1.4%) | |||||
| Others | 3 (2.1%) | Haemophilus spp. | 1 (0.7%) | Others | 21 (14.6%) | |||||
|
Stage III (N = 84) |
Streptococcus spp. | 29 (34.5%) | Lactobacillus spp. | 2 (2.4%) | Neisseria spp. | 2 (2.4%) | Enterobacter spp. | 5 (6.0%) | Prevotella spp. | 12 (14.3%) |
| Staphylococcus spp. | 6 (7.1%) | Actinomyces spp. | 1 (1.2%) | Escherichia coli | 2 (2.4%) | Fusobacterium spp. | 5 (6.0%) | |||
| Enterococcus spp. | 2 (2.4%) | Corynebacterium spp. | 1 (1.2%) | Pseudomonas spp. | 1 (1.2%) | Parvimonas micra | 2 (2.4%) | |||
| Granulicatella spp. | 1 (1.2%) | Bacillus spp. | 1 (1.2%) | Haemophilus spp. | 1 (1.2%) | Bacteroides spp. | 1 (1.2%) | |||
| Others | 3 (3.6%) | Rahnella spp. | 1 (1.2%) | Others | 6 (7.1%) |
Candida spp. were excluded from this table (N = 5, stage IV ORN 4, stage II MRONJ 1)
Abbreviations: GPC, gram-positive cocci; GPR, gram-positive rods; GNC, gram-negative cocci; GNR, gram-negative rods; MRONJ, medication-related osteonecrosis of the jaw; ORN, osteoradionecrosis of the jaw
Fifty-one patients were tested for antimicrobial susceptibility. Acquired resistant bacteria were detected in 40 patients (78.4%). The resistance rates for ABPC (AMPC), CLDM, macrolide antimicrobials, and quinolones commonly used in oral and maxillofacial surgery were investigated. The results showed that 31 (60.8%) patients were ABPC-resistant, 19 (37.4%) were CLDM-resistant, 30 (58.8%) were macrolide-resistant, and 16 (31.4%) were quinolone-resistant. A total of 197 bacterial strains were detected, 62 (31.5%) and 42 (21.3%) of which were completely resistant and ABPC-resistant strains, respectively (Table 3).
Table 3.
Detection rates for resistant bacteria
| Variables | Antimicrobial resistance | No effect of ABPC |
|---|---|---|
| Patients with resistant bacteria (N = 51) | 40 (78.4%) | 31 (60.8%) |
| Bacteria species (N = 197) | 62 (31.5%) | 42 (21.3%) |
| Gram positive cocci (92) | 46 (50.0%) | 15 (16.3%) |
| Streptococcus spp. (71) | 30 (42.3%) | 2 (2.8%) |
| Staphylococcus spp. (13) | 11 (84.6%) | 11 (84.6%) |
| Enterococcus spp. (4) | 4 (100%) | 2 (50.0%) |
| Others (4) | 1 (25.0%) | 0 |
| Gram positive rods (7) | 2 (28.6%) | 1 (14.3%) |
| Actinomyces spp. (2) | 0 | 0 |
| Corynebacterium spp. (2) | 1 (50.0%) | 1 (50.0%) |
| Others (3) | 1 (33.3%) | 0 |
| Gram negative cocci (3) | 0 | 0 |
| Gram negative rods (28) | 5 (17.9%) | 19 (67.9%) |
| Enterobacter spp. (10) | 2 (20.0%) | 10 (100%) |
| Escherichia coli (5) | 1 (20.0%) | 0 |
| Klebsiella spp. (4) | 0 | 4 (100%) |
| Pseudomonas spp. (2) | 1 (50.0%) | 2 (100%) |
| Citrobacter spp. (2) | 0 | 2 (100%) |
| Others (5) | 1 (20.0%) | 1 (20%) |
| Obligate anaerobes (67) | 9 (13.4%) | 7 (10.4%) |
| Prevotella spp. (30) | 6 (20.0%) | 5 (16.7%)* |
| Fusobacterium spp. (10) | 0 | 0 |
| Parvimonas micra (6) | 0 | 0 |
| Bacteroides spp. (2) | 2 (100%) | 2 (100%) |
| Orthers (19) | 1 (5.3%) | 0 |
Data are shown as median (first quartile, third quartile) or n (%)
Abbreviations: ABPC, ampicillin
*Beta-lactamase production
Factors associated with severity
Factors associated with disease severity were investigated in 51 patients who had results of susceptibility testing. Univariate analysis revealed statistically significant differences in age, type of osteonecrosis, history of cellulitis, period from diagnosis of osteonecrosis of the jaw to surgery, presence of gram-negative rods (Enterobacter spp.), and antimicrobial resistance (ABPC-resistant) between the severe disease (stage IV of ORN and stage III of MRONJ) and non-severe disease groups (Table 4). Therefore, a multivariate analysis was conducted using these variables as explanatory variables. The results showed statistically significant differences in MRONJ (underlying malignancy) and ABPC resistance between the two groups, with odds ratios of 13.5 (95% confidence interval [CI], 1.09–168; p = 0.043) and 8.74 (95% CI, 1.20–63.4; p = 0.032), respectively (Table 5). Enterobacter spp. were detected only in the severe disease group.
Table 4.
Univariate analysis of factors that affect the severity of osteonecrosis of the jaw
| Variables | Severe (n = 29) | Not severe (n = 22) | p value |
|---|---|---|---|
| Patient characteristics | |||
| Age (years) | 70 (66, 74) | 82 (67, 86) | 0.038* |
| Sex (male) | 13 (44.8%) | 4 (18.2%) | 0.072 |
| Body mass index | 20.4 (19.2, 23.1) | 20.9 (19.8, 23.2) | 0.216 |
| History of smoking | 6 (20.7%) | 4 (18.2%) | 1.000 |
| Alcohol consumption | 10 (34.5%) | 5 (22.7%) | 0.536 |
| Immunocompromised status | 16 (44.8%) | 12 (54.4%) | 0.577 |
| Cancer-bearing | 9 (31.0%) | 5 (22.7%) | 0.546 |
| Haematologic examination | |||
| Albumin (g/dL) | 3.8 (3.3, 4.1) | 3.7 (3.4, 3.9) | 0.793 |
| Haemoglobin (g/dL) | 12.0 (10.4, 13.1) | 11.3 (10.3, 13.2) | 0.620 |
| eGFR (mL/min/1.73m2) | 63.8 (57.7, 78.7) | 58.8 (46.3, 72.6) | 0.221 |
| White blood cell (/µL) | 5550 (4500, 7100) | 5900 (5100, 8300) | 0.515 |
| Neutrophil (/µL) | 3900 (2959, 5043) | 4213 (2968, 5760) | 0.613 |
| Lymphocyte (/µL) | 1160 (896, 1592) | 1475 (1263, 1718) | 0.275 |
| Osteonecrosis characteristics | |||
| Location | 0.728 | ||
| Maxilla | 5 (17.2%) | 5 (22.7%) | |
| Mandible | 24 (82.8%) | 17 (77.3%) | |
| Type of osteonecrosis | 0.010* | ||
| ORN | 13 (44.8%) | 4 (18.2%) | |
| MRONJ | |||
| For osteoporosis | 6 (20.7%) | 14 (63.6%) | |
| For malignancy | 10 (34.5%) | 4 (18.2%) | |
| Cellulitis | 21 (72.4%) | 8 (36.4%) | 0.021* |
| Duration from diagnosis to surgery (days) | 324 (77, 823) | 90 (46, 344) | 0.018* |
| Bacteria characteristics | |||
| Gram-negative rod | 17 (58.6%) | 5 (22.7%) | 0.013* |
| Enterobacter spp. | 10 (34.5%) | 0 | 0.003* |
| Others | 7 (24.1%) | 5 (22.7%) | 1.000 |
| Antimicrobial resistance | |||
| ABPC | 23 (79.3%) | 8 (36.4%) | 0.003* |
| CLDM | 9 (31.0%) | 10 (45.5%) | 0.383 |
| Macrolide | 15 (51.7%) | 15 (68.2%) | 0.266 |
| Quinolone | 9 (31.0%) | 7 (31.8%) | 1.000 |
Data are shown as median (first quartile, third quartile) or n (%)
* Statistically significant (p < 0.05)
ABPC, ampicillin; CLDM, clindamycin; eGFR, estimated glomerular filtration rate; MRONJ, medication-related osteonecrosis of the jaw; ORN, osteoradionecrosis of the jaw
Table 5.
Multivariate logistic regression analysis of factors that affect the severity of osteonecrosis of the jaw
| Variables | β | OR | 95% CI | p value | |
|---|---|---|---|---|---|
| Lower | Upper | ||||
| Age | -0.04 | 0.96 | 0.87 | 1.05 | 0.389 |
| Cellulitis | 0.94 | 2.57 | 0.40 | 16.7 | 0.322 |
|
Type of osteonecrosis (Ref. MRONJ [osteoporosis]) |
|||||
| MRONJ (malignancy) | 2.61 | 13.5 | 1.09 | 168 | 0.043* |
| ORN | 1.32 | 3.76 | 0.31 | 45.8 | 0.299 |
| Duration from diagnosis to surgery | < 0.01 | 1.00 | 1.00 | 1.00 | 0.508 |
| Gram-negative rods | 1.01 | 2.75 | 0.39 | 19.4 | 0.310 |
| ABPC resistance | 2.17 | 8.74 | 1.20 | 63.4 | 0.032* |
* Statistically significant (p < 0.05)
Abbreviations: ABPC, ampicillin; CI, confidence interval; MRONJ, medication-related osteonecrosis of the jaw; OR, odds ratio; ORN, osteoradionecrosis
Discussion
In this study, we analysed tissue cultures of bacteria associated with osteonecrosis of the jaw and evaluated the association between the identified bacteria species and the severity of osteonecrosis of the jaw. The results of this study indicated that the bacteria associated with osteonecrosis of the jaw have a similar composition to that of bacteria associated with common odontogenic infections, but a higher proportion of gram-negative rods (especially in samples from patients with ORN). In addition, we observed that Enterobacter spp. were detected only in severe cases. Furthermore, the severity of osteonecrosis of the jaw was associated with the presence of ABPC-resistant bacteria (an approximately 9-fold increased risk) and the type of osteonecrosis of the jaw (underlying malignancy in MRONJ) (an approximately 14-fold increased risk). To our knowledge, the present study is the first study conducted to examine the association between bacteria and the severity of osteonecrosis of the jaw.
The oral cavity has endemic flora, and contamination during bacteriological examinations is unavoidable. Therefore, it is important to reduce the risk of contamination to ensure accurate identification of causative agents. Current guidelines indicate that in the management of diabetic foot lesions, which is a leading chronic infectious disease, the specimens should be taken from tissue as deeply as possible for bacterial testing before initiation of antimicrobial therapy [27]. In addition, it is recommended that tissue culture be performed in such cases instead of swab testing [28]. As we considered that bacterial testing should also be adopted for osteonecrosis of the jaw, the specimens in this study were obtained from tissue as deeply as possible.
In this study, oral Streptococcus spp. and obligate anaerobes were the bacteria predominantly detected in tissue cultures, with a composition similar to that observed in common odontogenic infections [13, 26, 29]; however, a higher proportion of gram-negative rods was detected in the present study. The bacteria detected in the present study are similar to those reported in previous studies [10, 14, 30, 31]. Among the gram-negative rods, Enterobacter spp. were most frequently detected in the present study. Notably, similar findings have been reported in previous studies [32]. The high proportion of gram-negative rods detected in the present study could be attributed to a long-term medical history of treatment of the primary disease and microbial substitution due to long-term use of antimicrobials [31]. However, narrow-range penicillins such as ABPC are typically the first choice for odontogenic infections because Streptococcus spp. are the primary causative organisms in such cases [12]. As Streptococcus spp. were also detected in most specimens in the present study, penicillins were the first choice of treatment for the patients. However, the detection rate for ABPC-resistant bacteria was as high as approximately 60%, which is comparable to that reported in a previous study [31]. In addition, Enterobacter spp. and Klebsiella spp., which were detected in the present study, are naturally resistant to penicillins. Moreover, many gram-negative rods (e.g. Pseudomonas spp.) are not in the ABPC spectrum. Therefore, if antimicrobial treatment is necessary, empirical treatment should be started with a penicillin-based antimicrobial combined with a beta-lactamase inhibitor; thereafter, the drug can be changed to a suitable antimicrobial based on the bacterial culture results.
Factors associated with the severity of osteonecrosis of the jaw were examined in this study, and the results suggested that ABPC-resistant bacteria are associated with osteonecrosis of the jaw. Necrotic bones have poor blood flow and are difficult to treat using antimicrobials. Therefore, it is necessary to physically remove the necrotic tissue to reduce the quantity of the bacteria present. However, complete debridement is often difficult if the patient’s general condition and the boundaries of the necrotic bone are unclear. Therefore, conservative treatments such as washing and administering antimicrobials are often used in clinical practice [33]. Frequent use of the oral antimicrobials CVA/AMPC and AMPC was observed in the present study. However, macrolides and quinolones may have been used in a diffuse manner. Therefore, accumulation of resistant bacteria in the necrotic bone and difficulty achieving complete debridement may have contributed to the spread of the lesions. This indicates that it is important to remove necrotic bone whenever possible and encourage the appropriate use of antimicrobials, even in cases of osteonecrosis of the jaw [34]. In a recent study, aggressive surgical treatment yielded good results, particularly for patients with MRONJ [35].
Factors associated with severe ORN have been reported previously. These factors include age, irradiation dose, postoperative radiation, diabetes, heavy smoking, and heavy drinking [16, 17]. Notably, none of these factors were identified in the present study. The factors associated with MRONJ include younger age, hypoalbuminaemia (< 4.0 g/dL), maxillary onset, and chemotherapy (cancer-bearing) [18, 19]. In addition, failure to cure has been reported in patients with underlying disease (cancer) [19]. The results of the present study indicated that MRONJ resulting from the treatment of a malignancy is a critical factor associated with the severity of osteonecrosis of the jaw, a finding that is consistent with the results of previous studies. However, the wide range of the 95% CIs indicates that the results should be interpreted with caution. In this study, the number of surgically treated MRONJ cases was lower in patients with malignancy-related disease than in those with osteoporosis-related disease. This may be attributed to the poor general condition and limited prognosis of patients with malignancy, which often precludes surgical intervention.
This study has some limitations. First, the retrospective design of the study may have introduced observer and recorder bias into the data collection process. To reduce this bias, the data were collected and recorded by three independent observers (JK, MY, and MM). Second, as the risk of specimen contamination could not be completely eliminated, the true relevance of the detected bacteria remains unclear. This is the greatest limitation in the analysis of specimens obtained from the oral cavity. To combat this issue, samples were collected from multiple tissues as deeply as possible, thereby improving the reliability of the detected bacteria being the causative organism. Third, susceptibility testing was not performed in all cases. This means that susceptibility testing may have been actively conducted for bacteria with a high likelihood of becoming resistant; therefore, the risk of selection bias cannot be completely ruled out. Although the dosage and duration of antibiotic use may contribute to the development of resistant bacteria, this study did not investigate these factors, as they could not be determined from the current data alone. This remains an important area for future research. Fourth, all the patients included in this study underwent surgical treatment. Therefore, whether the results of this study can be directly applied to patients who have not undergone surgery is unclear. Nevertheless, it is advisable to actively perform tissue culture at any stage of osteonecrosis of the jaw to ensure the appropriate use of antimicrobials. As this was a retrospective study, future prospective studies with sufficient sample sizes are needed to validate the findings.
Conclusions
This study demonstrated that common odontogenic pathogenic bacteria such as Streptococcus spp. and obligate anaerobes are associated with both ORN and MRONJ. Notably, gram-negative rods, particularly Enterobacter spp., were detected more frequently only in severe cases. The results of this study suggest that ABPC-resistant bacteria are involved in severe osteonecrosis of the jaw. Furthermore, the results indicate that MRONJ caused by the use of ARAs for the treatment of malignant tumours have a high likelihood of being severe.
Statements and Declarations.
Supplementary Information
Below is the link to the electronic supplementary material.
Acknowledgements
Mari Kusuki at Kobe University.
Abbreviations
- eGFR
estimated glomerular filtration rate
- MRONJ
medication-related osteonecrosis of the jaw
- ORN
osteoradionecrosis of the jaw
Author contributions
This study was designed by JK. Data collection was performed by JK, MY, and MM. Most of the statistical analyses were performed by JK. The initial draft of the manuscript was written by JK. The manuscript was critically reviewed by EI, SF, and MA. All the authors read and approved the final manuscript and agree to be accountable for all aspects of this study.
Funding
Open access funding provided by Kagoshima University. The authors declare that no funds, grants, or other support were received during the preparation of this manuscript. Competing interests. The authors have no relevant financial or non-financial interests to disclose.
Data availability
The datasets used and analysed in the current study are available from the corresponding author upon reasonable request.
Declarations
Competing interests
The authors declare no competing interests.
Footnotes
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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Supplementary Materials
Data Availability Statement
The datasets used and analysed in the current study are available from the corresponding author upon reasonable request.