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. 2025 Feb 28;15:35. doi: 10.1186/s13568-025-01847-z

Best among the key molecular diagnostic markers of bacterial vaginosis

Tongyang Deng 1,#, Xiangquan Song 2,#, Qiumei Liao 4,✉, Ying Zheng 3, Hong Sun 1, Lianzhen Zhang 1, Xuejia Chen 5,✉
PMCID: PMC11871275  PMID: 40021583

Abstract

To assess bacterial vaginosis (BV)-related primary molecular diagnostic markers of Lactobacillus crispatus, Gardnerella vaginalis, Fannyhessea vaginae, bacterial vaginosis-associated bacteria 2 (BVAB-2), Megasphaera-1 and Megasphaera-2 and to discover molecular diagnostic indicators of BV with the most economic value for the efficient diagnosis of BV.All vaginal secretion specimens, including 122 BV-positive cases and 130 BV-negative controls were collected. First, quantitative polymerase chain reaction (PCR) was used to determine the levels of above the six bacteria. Then, the detection rates, sensitivity, specificity, diagnostic threshold, and receiver operating characteristic (ROC) curve were compared. Megasphaera-1 and Megasphaera-2 were detected in the BV-positive group, with a low detection rate of 35.25% and 19.67% respectively. The sensitivity and specificity of the above four bacteria were 95.90%/72.31%, 82.79%/92.48%, 72.13%/95.38%, and 56.56%/94.62% respectively, using the cut-off value for the diagnosis of BV. When combinations of L. crispatus with G. vaginalis, F. vaginae, and BVAB-2 were performed respectively, their sensitivity and specificity were 99.29%/97.79%, 98.86%/98.72%, and 98.22%/98.51% in sequence.It is difficult to diagnose BV using only one species, however, combinations of L. crispatus with G. vaginalis or F. vaginae showed a better diagnostic effect, particularly with the combination of L. crispatus and G. vaginalis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13568-025-01847-z.

Keywords: Bacterial vaginosis, Molecular diagnostic marker, Lactobacillus crispatus, Gardnerella vaginalis, Fannyhessea vaginae

Key points

L. crispatus combing with G. vaginalis had the following advantages:

  1. Compared with one bacteria, it can better reflect the idea of vaginal microflora;

  2. Compared with 4 to 6 indicators, it was with lower cost and easily explored reagent kits;

  3. Compared with Nugent score, it was accurate and repeatable;

Supplementary Information

The online version contains supplementary material available at 10.1186/s13568-025-01847-z.

Introduction

Bacterial vaginosis (BV) is one of the most common gynecological diseases, associated with a decrease in the abundance of Lactobacillus species, an increase of anaerobic bacteria, and abundant microbial imbalance (Chang et al. 2013; van de Wijgert et al. 2014). Also, it is related to premature birth, miscarriage (Hay et al. 1994), neonatal infection (Svare et al. 2006), infertility (Spandorfer et al. 2001) and pelvic inflammation (Ness et al. 2005), Furthermore, BV may also increase the risk of Gonococcal, Chlamydial, and Trichomonal genital infection (Brotman et al. 2010) and other sexually transmitted diseases, vulnerability to infection by the human immunodeficiency virus (van de Wijgert et al. 2008), which has become one of the major public health challenges faced by women of childbearing age. The global prevalence of BV in women ranges from 23 to 29%, black women in North America is 33% (Peebles et al. 2019), with a cure rate of 65–85% (Oduyebo et al. 2009), however, it usually recurs within weeks to months after cure at a rate of 23–58% (Donders et al. 2014; Larsson and Forsum 2005; Marrazzo et al. 2008), which severely affects the physical health of the patients and their family.

The Amsel criteria are one of the accepted standards for the diagnosis of BV (Amsel et al. 1983). The presence of three out of the following four positive criteria indicates that the cause of vaginal complaints is BV: (i) clue cells on microscopy; (ii) release of a “fishy” odor upon addition of 10% potassium hydroxide solution; (iii) pH of the vaginal fluid > 4.5; (iv) thin, white, yellow, homogeneous discharge; however, its sensitivity is only 37–70% in practice (Schwebke et al. 1996; Sha et al. 2005). Since there is great subjectivity and the characteristics of secretions and the smell of fish, these criteria are limited in practical application. Alternatively, BV is diagnosed using the Nugent Score of vaginal secretion (VS). Smears of vaginal discharge are Gram-stained, and morphological recognition of Lactobacillus, Gardnerella, and Mobiluncus is performed under oil immersion and scored according to certain regulations. A Nugent score system is used: 0–3 is considered “negative” for BV, 4–6 is considered “indeterminate” for BV, and 7–10 is considered to indicate BV (Nugent et al. 1991). However, using the Nugent Score requires highly trained and experienced staff. Moreover, reliance on morphology for identifying bacteria is subjective and can lead to misidentification of bacteria (Klebanoff et al. 2004; Modak et al. 2011). The Hay-Ison standard (Ison and Hay 2002) is an alternative for diagnosing BV, which is proposed by the European International Federation for sexually transmitted disease Control. The method is divided into five grades (from 0 to 4) and used simply and entirely. However, it has the same problem as the Nugent score.

To accurately recognize and quantitatively detect bacteria of vaginal discharges, novel molecular diagnostic means have been explored. Studies have shown that BV was mainly related to G. vaginalis (recently described as Gardnerella spp. (Vaneechoutte et al. 2019) ), F. vaginae (previously described as Atopobium vaginae (Nouioui et al. 2018), Megasphaera spp., Leptotrichia amnionii, Sneathia sanguinegens, Porphyromonas asaccharolytica, bacterial vaginosis-associated bacteria (BVAB-1, BVAB-2, and BVAB-3), etc. (Fredricks et al. 2005; Onderdonk et al. 2016; Tamrakar et al. 2007). Although there are currently 4–7 kinds of molecular detection markers in the market, as well as commercial kits for the quantitative detection of BV through G. vaginalis by itself, specific molecular markers from various commercial kits have not yet formed a unified standard (Coleman and Gaydos 2018). If too many diagnostic markers are selected, the cost of diagnostic reagents will rise accordingly, and the interpretation of the test results will easily confuse obstetricians and gynecologists as different molecular indicators can produce conflicting results sometimes. However, it is difficult to reflect the status of vaginal microbiota imbalance with a single bacterium detection. Therefore, to accurately reflect the balance of vaginal microbiota, reasonable BV diagnostic markers should include healthy bacteria in the vagina and BV-related bacteria that causes vaginal bacterium imbalance. Of Lactobacillus, besides L. crispatus, L. gasseri, L. jensenii and other species also can produce lactic acid and H2O2 (O’Hanlon et al. 2011; Ravel et al. 2011; Tachedjian et al. 2017; Zozaya-Hinchliffe et al. 2010), another our previous study revealed that L. crispatus is of the higher detection rate in the healthy women and better specificity for the diagnosis of BV (Deng et al. 2022). Consequently, L. crispatus and the BV-related bacteria such as G. vaginalis, F. vaginae, BVAB-2 (recently named as Oscillospiraceae bacterium strain CHIC02 (Osei Sekyere et al. 2023), Megasphaera-1, and Megasphaera-2 are used to commercial reagent kits as BV diagnostic markers (Coleman and Gaydos 2018). To reduce the detection number of molecular indicators as much as possible and accurately diagnose BV, we re-evaluated the above six kinds of bacteria and screened out molecular diagnostic indicators with the highest cost-effective and clinical practical value based on previous studies.

Materials and methods

Ethics

This study has been approved by the Medical Ethical Committee of Tongde Hospital of Zhejiang Province, China (no.: 2021056).

Participants

For BV negative group (N group), the inclusion criteria were females: (i) more than 18 years of age; (ii) with a regular menstrual cycle; (iii) who were not using vaginal contraceptives; (iv) without Candida spp., Neisseria gonorrhoeae, Chlamydia trachomatis, Trichomonas vaginalis, HIV; (v) who had not used antibiotics in the previous three months; (vi) without sexual intercourse within 24 h; (vii) a Nugent Score of 0–3, a VS pH of 3.8–4.5, and a cleanliness degree of vagina is I–II (Cleanliness degree is classified into IV grades according to their numbers of Leukocytes, epithelial cells, Lactobacillus and coccus in the vaginal secretion, cleanliness degree I or II means to healthy women.). The VSs of the participants had a normal appearance without a fishy odor, and vaginal itching/burning sensations were absent. For the BV-positive group (BV group), the inclusion criteria were females: (i) more than 18 years of age; (ii) who had not used antibiotics in the previous three months; (iii) without sexual intercourse within 24 h; (iv) and a Nugent score of 7–10.

Specimen collection and processing

A gynecologist used a sterile swab to wipe off secretions outside the vulva. Two sterile nylon vaginal swabs were then placed into the lower one-third of the vagina, whirled for two cycles to obtain VS, and were subsequently sent for analysis within 1 h. In one sample, adding 0.5 mL of physiologic (0.9%) saline, taking out a drop of mixture to measure the degree of cleanliness, presence of Candida (adding 10%KOH solution before microscopy) and Trichomonas vaginalis through microscopic examination, other routine tests and Gram staining for the Nugent Score. Another sample was immediately stored at − 80 °C for DNA extraction and polymerase chain reaction (PCR) detection.

DNA extraction

DNA was extracted using the Multi-type Sample DNA/RNA Extraction-Purifucation Kit (magnetic beads method) from the Shengxiang Biological Technological company in Hunan, China. DNA was extracted as per the instructions of the manufacturer kit (Reagent type: S 1006, Lot number: 2020004). The extraction flow was as follow: 200µL VS specimens were added into the extraction solution, and the DNA extraction process was completed after a series of steps such as mixing, cell lysis at 95℃, centrifugation, resting, elution and magnetic bead separation. Then nuclear purity was measured using Qubit™ 2.0 (Thermo Fisher, Waltham, MA, USA). Extracted DNA was analyzed by a spectrophotometer at wavelengths of 260 nm (excitation) and 280 nm (emission). DNA was stored at − 40℃ for preparation.

Quantitative PCR detection

DNA extracted from VSs were used for PCR detection of L. crispatus, G. vaginalis, F. vaginae, BVAB-2, Megasphaera-1, and Megasphaera-2 through 7500 Real-time PCR system (Applied Biosystems, Foster City, CA, USA). The reagent kit (Thermo Fisher) mainly includes TaqMan Fast Advanced Master Mix, TaqMan Gene Expression Assay (including primers and probes) and TaqMan Vaginal Microbiota Amplification Control. TaqMan Vaginal Microbiota Amplification Control was a linearized multi-target plasmid with a concentration of 1.0 × 105copies/µL, which was diluted into different levels as standard substance for the standard curve, the results were 1.0 × 105 copies/µL, 1.0 × 104 copies/µL, 1.0 × 103 copies/µL, 1.0 × 102 copies/µL respectively. The total reaction volume of 20 µL contained: 20× TaqMan Gene Expression Assay (1.0 µL), 2× TaqMan Gene Expression Master Mix (10.0 µL), DNA template (4.0 µL), and double-distilled H2O (5.0 µL). The PCR parameters were programmed as follows: 50 °C for 2 min, 95 °C for 10 min for the pre-denaturation step, 95 °C for 15 s for the denaturation step, and 60 °C for 1 min for the annealing extension step. The program was run for a total of 40 cycles.

Sterile physiological saline was used as no template control, and mixed bacteria solution without target bacteria was utilized as negative control, additionally, vaginal secretions including bacteria to be tested were used as positive sample control, diluted liquid of TaqMan Vaginal Microbiota Amplification Control with a concentration of 1.0 × 103 copies/µL was used as positive control.

Negative control production process: Firstly, to select bacterial colony of Staphylococcus aureus ATCC29213, Enterococcus faecalis ATCC29212, Staphylococcus saprophyticus ATCC BAA-750, Enterobacter hormaechei ATCC700323, Escherichia coli ATCC25922, and Pseudomonas aeruginosa ATCC27853 from the Columbia blood plate, secondly, to prepare with a 0.5 McFarland turbidity equivalent to 1.0 × 105cfu/ml bacterial liquid using 0.9% physiological saline, then to extract DNA from above five bacteria mixed into one tube in equal volumes according to the DNA extraction instruction, lastly, to store extracted DNA at -20 °C for preparation.

Positive sample control preparation process: 20 vaginal secretion samples with Nugent scores of 0–3 were used to extract DNA respectively, all extracted DNA mixed into one tube was detected Lactobacillus crispatus by digital PCR method, it will be stored as positive sample control for preparation as soon as the result is positive. Using similar method, 40 vaginal secretion samples with Nugent scores of 7–10 were used to extract DNA respectively, and all extracted DNA mixed into one tube was used to determine G. vaginalis, F. vaginae, BVAB-2, Megasphaera-1, and Megasphaera-2, it will be stored as positive sample control for preparation as soon as above five bacteria are all existent.

Statistical methods

An independent sample t-test was used to compare the ages of the two groups, and the Chi-square test was used to compare the detection rate in the two groups. SPSS22.0 software was used to count, and P < 0.05 was considered as statistical significance. GraphPad Prism 8.3 software was used to analyze the receiver operating characteristic (ROC) curve, area under the curve, 95% confidence intervals and P value.

Results

Clinical information of study participants

The characteristics of the BV-negative group were as follows: (i) The group included 130 cases; (ii) age: 33.05 ± 7.65; (iii) with the cleaning degree being I-II; (iv) pH of 3.8–4.4; (v) Nugent score of 0–3. The characteristics of the BV-positive group were as follows: (i) The group included 122 cases; (ii) age: 33.85 ± 8.64; (iii) with the cleaning degree being III–IV; (iv) pH of 4.5–5.4; (v) Nugent score of 7–10. There was no statistical significance between ages in BV-negative and BV-positive groups by an independent sample t-test (t = 0.785, P = 0.433).

Detection rates of L. crispatus and other five kinds of BV-related bacteria in the vaginal secretions

The top three bacteria detected in the BV-negative group were L. crispatus, G. vaginalis, F. vaginae, and their detection rates in the BV-negative were 76.92%, 26.15%, and 24.62%, respectively, while in the BV-positive group, they were 18.85%, 94.26%, and 87.70%, respectively. Based on these findings, L. crispatus can be utilized as beneficial bacterial markers in the vaginal microbiota, and the latter two may be BV-positive related diagnostic markers. The detection rates of Megasphaera-2, Megasphaera-1, and BVAB-2 in the BV-negative group were very low, with a result of 1.54%, 1.54%, and 7.69%, respectively. Although they are BV associated bacteria, their detection rates are all not high as diagnostic markers, only accounting for 19.67%, 35.25%, and 60.66%, respectively. There were obvious differences for whichever of the six bacteria between the BV-positive and the BV-negative group by chi-square test (P < 0.001), and the detailed data are presented in Table 1. The scattered plot of the qPCR copy number of each bacteria after taking the logarithm to the base on ten is shown in Fig. 1.

Table 1.

Detection rates of L. crispatus and other five kinds of BV-related bacteria in the vaginal secretions

Bacteria name Megasphaera-1 Megasphaera-2 L. crispatus BVAB-2 G. vaginalis F. vaginae

Detection

condition

Detected/Not

detected

 Detection rate (%)

Detected/Not

detected

 Detection rate (%)

Detected/Not

detected

 Detection rate (%)

Detected/Not

detected

 Detection rate (%)

Detected/Not

detected

 Detection rate (%)

Detected/Not

detected

 Detection rate (%)
BV-negative group (n = 130) 2/128 1.54 2/128 1.54 100/30 76.92 10/120 7.69 34/96 26.15 32/98 24.62
BV-positive group (n = 122) 43/79 35.25 24/98 19.67 23/99 18.85 74/48 60.66 115/7 94.26 107/15 87.70
Chi-square value 48.750 22.366 84.940 79.445 120.800 101.280
P value 0.000 0.000 0.000 0.000 0.000 0.000
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Fig. 1.

Fig. 1

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Scattered plot through quantitative detection method for all types of bacteria related to bacterial vaginosis (BV) in the positive and negative group. The copy results of each bacteria which was log-10 transformed is shown in the y-axis, and a value near 0 to the x-axis indicates that the bacteria is absent or too low. Group N means negative group and Group B means positive group

Sensitivity and specificity of L. crispatus, G. vaginalis, F. vaginae, and BVAB-2

Owing to their low detection rates, we did not further evaluate Megasphaera-1 and Megasphaera-2. However, we analyzed the ROC curves of L. crispatus, G. vaginalis, F. vaginae, and BVAB-2 to diagnose BV and their areas under the ROC curves, their areas were 0.8484, 0.9292, 0.8736, and 0.7622, respectively (detailed data are shown in Fig. 2; Table 2). The diagnostic threshold, sensitivity, and specificity of the above four bacteria for the diagnosis of BV are presented in Table 3. These results indicated that the sensitivity of L. crispatus may reach 95.90%, while the specificity is only 72.31%. The specificity of BVAB-2 may reach 94.62%, whereas the sensitivity is merely 56.56%.

Fig. 2.

Fig. 2

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Receiver operating characteristic (ROC) curve for the four kinds of bacteria. The bacteria names are abbreviated: L. crispatus, Lactobacillus cripatus; G. vaginalis, Gardnerella vaginalis; F. vaginae, Fannyhessea vaginae; BVAB-2, bacterial vaginosis-associated bacteria 2

Table 2.

Areas under receiver operating characteristic (ROC) curve for the four kinds of bacteria

Bacterial name Area 95% confidence interval P value
L. crispatus 0.8484 0.7978–0.8990 < 0.0001
G. vaginalis 0.9292 0.8954–0.9631 < 0.0001
F. vaginae 0.8736 0.8276–0.9197 < 0.0001
BVAB-2 0.7622 0.7010–0.8234 < 0.0001
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Table 3.

Diagnostic threshold, sensitivity, specificity, and other indicators for the four kinds of bacteria

Bacterial name Threshold value (log10copy) Sensitivity (%) Specificity (%) PPV (%) NPV (%)
L. crispatus < 5.840 95.9 72.31 76.47 94.95
G. vaginalis > 4.125 82.79 92.48 91.82 85.21
F. vaginae > 3.930 72.13 95.38 94.17 83.22
BVAB-2 > 0.4800 56.56 94.62 97.18 70.72
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Combined scheme of L. crispatus with G. vaginalis, F. vaginae, and BVAB-2, respectively

Considering the diagnostic efficacy of individual bacteria, none of the four bacteria could perfectly demonstrate sensitivity and specificity. Therefore, to improve the diagnostic sensitivity and specificity of BV, a combined plan was established. For example, when L. crispatus was combined with G. vaginalis, and Log10 (L. crispatus) < 5.840 or Log10 (G. vaginalis) > 4.125, BV was diagnosed as positive, and when both Log10 (L. crispatus) ≥ 5.840 and Log10 (G. vaginalis) ≤ 4.125 are all coexistent, BV was diagnosed as negative. The combined test results are shown in Table 4. When L. crispatus was combined with G. vaginalis, it presented the high sensitivity (99.29%) and specificity (97.79%). Moreover, the two bacteria have a high detection rate and copy number in VSs, which makes them ideal indicators for diagnosing BV.

Table 4.

Sensitivity and specificity of parallel and serial tests with the different bacterial combination plan

Bacterial name Parallel test sensitivity (%) Parallel test specificity (%) Serial test sensitivity (%) Serial test specificity (%)
L. crispatus & G. vaginalis 99.29 66.87 79.40 97.79
L. crispatus & F. vaginae 98.86 68.97 69.17 98.72
L. crispatus & BVAB-2 98.22 68.42 54.24 98.51
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Discussion

Currently, for diagnosing BV, the Nugent score and the Amsel criteria are regarded as the diagnostic gold standard. Molecular diagnosis has been used owing to its accuracy in identification and quantification to detect various bacteria including fastidious bacteria, and it will probably become the developing trend in future diagnosis (Adzitey et al. 2013). Some commercial reagent kits have already been used to diagnose BV (Coleman and Gaydos 2018), however, there is no consensus regarding which kind of bacteria to be selected as an indicator. Additionally, cost control and whether these markers can be made as point-of-care testing (POCT) items are also important factors to be considered (Redelinghuys et al. 2020). Lactobacillus, as the main beneficial bacteria of vaginal microbiota and a lot of BV-related bacteria which gives rise to bacterial imbalance have been reported in previous studies. Our study and previous research results consistently believed that it was not feasible to diagnose BV only through one species (Coleman and Gaydos 2018; Deng et al. 2022). Though some reagent kits may be used to improve indicator specificity by setting the detected threshold, we believe that at least two kinds of indicators (including Lactobacillus and at least one pathogenic bacteria related to BV) are needed to accurately reflect the microbiota imbalance.

After evaluating the six frequently-used indicators of diagnosing BV, we found that Megasphaera-1 and Megasphaera-2 separated from the BV- positive group had a better specificity, but they had low detection rate, with 35.25% and 19.67%, respectively, therefore neither of them is suitable to be used as markers for the diagnosis of BV. Some studies have found that BVAB-2 was closely related to BV (Cartwright et al. 2012; Fredricks et al. 2005, 2007; Hilbert et al. 2016), and we also found in this study there is a significant difference about the detection rate between the positive and the negative group. But the detection rate of BVAB-2 in the BV-positive group was only 60.66%, it still could not meet the requirements as a good marker.

Some studies highlighted that G. vaginalis and F. vaginae were very important markers for diagnosing BV (Jean-Pierre et al. 2008; Redelinghuys et al. 2017; Zozaya-Hinchliffe et al. 2010). In this study, G. vaginalis was isolated from the BV-positive group, with a detection rate of 94.26%, which is lower than that in some studies (98–100%) (Fredricks et al. 2005; Totten et al. 1982). G. vaginalis was detected in the BV-negative group, accounting for 26.15%. while in some previous studies, the results reported ranges from 36–55% (Cartwright et al. 2012; Eschenbach et al. 1988; Fredricks et al. 2007; Krohn et al. 1989; Spiegel et al. 1983). For the BV-negative group, the detection rate of F. vaginae (24.62%) was approximate to that of G. vaginalis (26.15%) in the study, however, the detection rate is higher than that of some studies (12–19%) (Bradshaw et al. 2006; Fredricks et al. 2005; Verhelst et al. 2004). The differences of bacteria detection rate may be caused by participants, ethics, region, life surrounding, and detection methods, etc (Joseph et al. 2021). Additionally, PCR detection method used in the study is also influenced by primer design, reaction system, and amplification conditional set in the reagent kits. In this study, the detection rate of G. vaginalis is higher than that of F. vaginae in the BV-positive group. When all the original data were transformed into the cut-off value, the sensitivity of G. vaginalis was higher than that of F. vaginae (82.79% vs. 72.13%), while the specificity of F. vaginae was higher than that of G. vaginalis (95.38% vs. 92.48%). After synthesizing the detection rate, sensitivity, specificity, and the AUC value of the ROC curve, we found that G. vaginalis was superior to F. vaginae for the diagnosis of BV, which is consistent with the opinion of selecting G. vaginalis to diagnose BV from commercial BD reagent kits (Coleman and Gaydos 2018).

The study results revealed that L. crispatus separated from the BV-negative group had a detection rate of 76.92% and its sensitivity reached 95.9%, whereas the specificity was only 72.31%. This study and previous studies indicated that the sensitivity and specificity of any of the above bacteria cannot simultaneously meet the requirements for diagnosing BV (Cartwright et al. 2012). Consequently, parallel and serial tests for L. crispatus combined with G. vaginalis, F. vaginae, and BVAB-2, respectively, were performed. The results presented that any of the above three combinations is positive (lower or higher than the reference cut-off value), its sensitivity is more than 98%; however, when any of the three combinations is negative, the specificity reaches more than 97%, and all the combined tests obtained excellent diagnosis efficacy. Since BVAB-2 was detected at a very low detection rate from the BV-positive group, only the combination of L. crispatus with G. vaginalis or L. crispatus with F. vaginae is recommended, and they both had similar diagnostic efficacy. However, when summing up the rate of bacteria detected and the concentration of specimens, the combination of L. crispatus and G. vaginalis is recommended as the most efficient and economical choice.

For combined diagnostic plan of different molecular markers about BV, previous studies mainly combine with two or more kinds of BV-related bacteria (Cartwright et al. 2012; Hilbert et al. 2016; Jean-Pierre et al. 2008), but we finally selected one kind of lactobacilli and one kind of BV-related bacteria as combined indicators, which is similar to the concept of Nugent score and Hay-lson criteria. Also, it may let clinicians learn the number of healthy bacteria in the vaginal microbiota, Furthermore, if only using BV-related bacteria as combined indicators to diagnose BV, it will also misjudge BV-intermediate with normal number of lactobacilli as BV. The study defect is that combined plan was not used to diagnose the BV-intermediate group.

In the study, six molecular indicators of BV that are widely accepted in the market have been comprehensively evaluated. The detection rate, sensitivity, specificity, ROC curve, and other aspects were evaluated, and the corresponding cut-off value was established. The study demonstrated that a combination of L. crispatus with G. vaginalis or L. crispatus with F. vaginae may be utilized as a BV diagnostic marker; of the combinations, combination plan of L. crispatus combing with G. vaginalis has a better effect, when compared with one single species, it can better reflect the vaginal microbiota balance, and compared with 4–7 indicators, it has a lower cost. Moreover, it is easier to explore multi-PCR reagent kits, even POCT reagent kits. Compared with the morphology diagnostic method such as Nugent score, Hay-lson criteria and Amsel criteria, the combination of two markers is more accurate and repeatable, and which will help offer potential quantitative and continuous monitoring markers for recurrent BV diagnosis in the future.

Electronic supplementary material

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Supplementary Material 1 (323.8KB, pdf)
Supplementary Material 2 (2.6KB, docx)

Abbreviations

L. crispatus

Lactobacillus crispatus

G. vaginalis

Gardnerella vaginalis

F. vaginae

Fannyhessea vaginae

VS

Vaginal secretion

PCR

Polymerase chain reaction

ROC

Receiver operating characteristic

AUC

Area under the curve

BV

Bacterial vaginosis

POCT

Point-of-care testing

BVAB-2

Bacterial vaginosis-associated bacteria 2

ATCC

American Type Culture Collection

Author contributions

T.D. and X.C. contributed to the conception and design of this study. Y.Z., H.S., L.Z., and Q.L. collected and organized the data. T.D., X.S., Y.Z., H.S., L.Z., Q.L., and X.C. analyzed the data. T.D., X.S., H.S., L.Z., and X.C. drafted the article. All the authors have read and approved the final article.

Funding

This work was supported by the Basic Public Welfare Research Project of Zhejiang, China (No. LGC22H200014).

Availability of data and material

The data obtained and /or analyzed in this study are available from the corresponding author upon reasonable request.

Declarations

Ethical statement

The study was conducted according to the principles of the Declaration of Helsinki and approved by the Medical Ethics Committee of Tongde Hospital of the Zhejiang Province, China. All study participants provided written informed consent for research and publication. The participants provided their written informed consent to participate in this study.

Competing interest

No potential conflict of interest was reported by the authors.

Footnotes

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Xiangquan Song and Tongyang Deng have contributed equally to this work as co-first author.

Contributor Information

Qiumei Liao, Email: 675646034@qq.com.

Xuejia Chen, Email: dty007005@163.com.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Supplementary Material 1 (323.8KB, pdf)
Supplementary Material 2 (2.6KB, docx)

Data Availability Statement

The data obtained and /or analyzed in this study are available from the corresponding author upon reasonable request.

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