Topical Penile Microbicide Use by Men to Prevent Recurrent Bacterial Vaginosis in Sex Partners: A Randomized Clinical Trial

Assessment and Treatment of Vaginitis

Vaginitis is the presenting symptom at millions of office visits each year in the United States. Although treatment of sporadic cases is often straightforward, recurrent cases present both diagnostic and treatment challenges. Molecular diagnostic tests are likely superior to in-office microscopy for most clinicians and most cases. In both recurrent bacterial vaginosis and recurrent vulvovaginal candidiasis, national treatment guidelines recommend an extended treatment duration with one of the first-line agents. In cases in which such treatment is not successful, vaginal boric acid is likely the cheapest and easiest alternative option. New antifungal medications offer additional but limited treatment options. Probiotics are not recommended for prevention of vulvovaginal candidiasis; however, vaginal products containing Lactobacillus crispatus may have promise for recurrent bacterial vaginosis. Trichomoniasis should be treated with a 1-week course of metronidazole; this is the only sexually transmitted infection for which treatment recommendations vary by sex. In cases in which patients do not respond to initial treatment, the diagnosis should be reconsidered, and other potential causes such as desquamative inflammatory vaginitis, genitourinary syndrome of menopause, or vulvodynia should be considered.

Optimizing the vaginal microbiome as a potential strategy to reduce heterosexual HIV transmission

Bacterial vaginosis (BV) is a proinflammatory genital condition characterized by high vaginal bacterial diversity and a paucity of Lactobacillus species. BV has been linked to an elevated risk of HIV acquisition among HIV-negative women and of forward HIV transmission to male sex partners among women living with HIV (adjusted hazard ratios of 1.69 and 3.17, respectively), potentially by eliciting genital inflammation in women with BV and their male sex partners. BV is also highly prevalent among women in sub-Saharan Africa, suggesting that BV treatment may have potential as an HIV prevention strategy. BV is typically treated with antibiotics but recurrence rates are high, possibly because treatment does not directly promote Lactobacillus growth. More recently, BV treatment strategies incorporating live biotherapeutic lactobacilli have led to sustained optimization of the vaginal microbiome and a decrease in inflammatory biomarkers previously associated with HIV susceptibility. Future studies are urgently needed to evaluate BV treatment strategies that can optimize the vaginal microbiome in the long term through colonization with H₂ O₂ -producing vaginal lactobacilli and to assess whether vaginal microbiota optimization is able to reduce the risk of HIV transmission.

The role of the genital microbiota in the acquisition and pathogenesis of sexually transmitted infections

PURPOSE OF REVIEW

There are an estimated 374 million new sexually transmitted infections (STIs) worldwide every year. Our review article examines the current evidence of how STI acquisition, transmission, and pathogenesis is impacted upon by the genital microbiota, with a focus on epidemiological, biochemical, and immunological features.

RECENT FINDINGS

At least in women, a genital microbiota dominated by lactobacilli has long been considered optimal for reproductive health, while depletion of lactobacilli may lead to a genital microenvironment dominated by anaerobic pathogens, which can manifest clinically as bacterial vaginosis. Recent research efforts have characterized genital microbiota composition in greater resolution, sometimes at species-level, using proteomics, metabolomics, and deep sequencing. This has enhanced our understanding of how specific microbiota members influence acquisition or clinical manifestation of STI pathogen infection. Other advances include a steady, though still slow, increase in the number of studies that sought to determine the genital (penile or urethral) microbiota of males and how it may impact that of their female partners' genital microbiota and risk of STI acquisition. Altogether, these data enabled us to explore the concept that genital microbiota may be sexually transmitted and influence pathogenesis and clinical presentation of other STI.

SUMMARY

With STI infection rates increasing worldwide, it is important now more than ever to find novel STI prevention strategies. Understanding if and how the genital microbiota is a modifiable risk factor for STI transmission, acquisition, and clinical manifestation may prove to be an important strategy in our efforts to curb morbidity in at risk populations.

Hormonal contraceptive use and the risk of sexually transmitted infections: a systematic review and meta-analysis

There are 150 million women worldwide using combined or progestogen-only hormonal contraceptive methods who may be at risk of sexually transmitted infections (STIs). Previous systematic reviews that have sought to establish whether there is an aetiological association between hormonal contraceptive methods/use and STIs have been limited in their methods and have mixed findings. We sought to update these reviews using appropriate control groups. We undertook a systematic review following the PRISMA guidelines and meta-analysis to examine the association between the use of all hormonal contraceptive methods and the acquisition of STIs (Neisseria gonorrhoeae, syphilis/Treponema pallidum, Chlamydia trachomatis, herpes simplex virus, and Trichomonas vaginalis) and/or bacterial vaginosis in literature published between 2005 and 2020. We analysed the effect of hormonal contraceptive methods/use separately on the prevalence, incidence and recurrence of STIs. A total of 37 studies were included in this review that reported 61 associations, in which 27 prevalence, eight incidence and two recurrence studies provided 43, 16, and two associations, respectively. We observed a positive association between hormonal contraceptive methods/use and the risk of chlamydia and herpes but a negative association for trichomoniasis and vaginosis. A negative but statistically insignificant association was observed between hormonal contraceptive methods/use and gonorrhoea. Hormonal contraceptive methods/use influences a woman's risk of STIs/ bacterial vaginosis, but the risk may differ depending on the type of STI. These findings should be contextualized carefully, particularly when formulating practice guidelines and policy, as the effects of hormonal contraceptive methods/use on the risk of STIs varied in direction when analysed separately by STI.

A Summary of the Sixth International Workshop on Microbiome in HIV Pathogenesis, Prevention, and Treatment

In October of 2020, researchers from around the world met online for the sixth annual International Workshop on Microbiome in HIV Pathogenesis, Prevention, and Treatment. New research was presented on the roles of the microbiome on immune response and HIV transmission and pathogenesis and the potential for alterations in the microbiome to decrease transmission and affect comorbidities. This article presents a summary of the findings reported.

Treatment of Male Sexual Partners of Women With Bacterial Vaginosis: A Randomized, Double-Blind, Placebo-Controlled Trial

BACKGROUND

We aimed to determine if treatment of male sexual partners of women with recurrent bacterial vaginosis (BV) with oral metronidazole 2×/day for 7 days (ie, multidose metronidazole) significantly decreased BV recurrence rates in the female.

METHODS

This was a multicenter, 2-arm, double-blind, placebo-controlled study. Women with recurrent BV and current diagnosis of BV by Amsel and Nugent were enrolled. Multidose metronidazole for 7 days was dispensed to women. Male partners were randomized to placebo versus multidose metronidazole for 7 days and asked to refrain from unprotected sex for 14 days. Female follow-up visits were conducted at day 21 and 8 and 16 weeks. Male follow-up visits occurred at days 14-21. BV cure was defined as 0-2 Amsel criteria and Nugent score 0-6 in the female partner with the primary endpoint at 16 weeks.

RESULTS

214 couples were enrolled. In the intent-to-treat population, there was no significant difference between treatment arms for the primary outcome. BV treatment failure occurred in 81% and 80% of women in the metronidazole and placebo arms through the third follow-up visit, respectively (P > .999). However, women whose male partners adhered to study medication were less likely to fail treatment (adjusted relative risk, .85; 95% CI, .73-.99; P = .035). This finding persisted in post hoc comparisons in the metronidazole arm.

CONCLUSIONS

Overall, this study did not find that male partner treatment with multidose metronidazole significantly reduces BV recurrence in female partners, although women whose partners adhered to multidose metronidazole were less likely to fail treatment.

CLINICAL TRIALS REGISTRATION

(NCT02209519).

A Summary of the Fifth Annual Virology Education HIV Microbiome Workshop

In October of 2019, researchers and community members from around the world met at the NIH for the fifth annual International Workshop on Microbiome in HIV. New research was presented on the role of the microbiome on chronic inflammation and vaccine design, interactions of genetics, environment, sexual practice and HIV infection with the microbiome and the development and clinical trials of microbiome-based therapeutic approaches intended to decrease the probability of HIV acquisition/transmission or ameliorate sequelae of HIV. The keynote address by Dr. Jacques Ravel focused on his work on the vaginal microbiome and efforts to improve the analysis and resolution of microbiome data.

Novel Selective Inhibition of Lactobacillus iners by Lactobacillus-Derived Bacteriocins

Lactobacillus iners is often associated with vaginal dysbiosis and bacterial vaginosis (BV), which are risk factors for adverse gynecological and obstetric outcomes. To discover natural inhibitors of L. iners, cell-free culture supernatants (CFSs) from 77 vaginal human Lactobacillus strains and 1 human intestinal strain were screened for inhibitory activity. Three active strains were identified, and Lactobacillus paragasseri K7 (K7), a human intestinal strain, produced the most potent L. iners-inhibitory activity. The active material was purified from the K7 CFS and yielded three active peptides, identified as components of two different class IIb, two-peptide bacteriocins, gassericin K7A (GasK7A) and gassericin K7B (GasK7B). The peptides corresponded to the GasK7A α peptide and the GasK7B α and β peptides. While all three peptides exhibited individual activity against L. iners, GasK7B α was the most potent, with an MIC of 23 ng/ml (4 nM). When combined in equal amounts, the GasK7B α and β peptides showed synergistic inhibition, with an MIC of 2 ng/ml (each peptide at 0.4 nM). Among the four major vaginal Lactobacillus species, the K7 bacteriocins selectively inhibited L. iners All 21 strains of L. iners tested (100%) were inhibited by the K7 bacteriocins, whereas <20% of the vaginal Lactobacillus crispatus, L. jensenii, and L. gasseri strains were inhibited. The combination of the BV treatment metronidazole and K7 bacteriocins completely killed both L. iners and Gardnerella vaginalis in a coculture experiment to mimic BV conditions. In contrast, this treatment did not inhibit L. crispatus cultures.IMPORTANCELactobacillus iners is a prevalent species of the vaginal microbiome, but unlike other major vaginal Lactobacillus species, it is not considered protective against BV and can coexist with BV-associated bacteria. L. iners is generally the first Lactobacillus species to emerge following the treatment of BV with metronidazole, and mounting evidence suggests that it may contribute to the onset and maintenance of vaginal dysbiosis. The discovery of highly potent bacteriocins that selectively kill L. iners while sparing protective vaginal lactobacilli may provide novel pharmacological tools to better understand the roles of this enigmatic bacterium in vaginal ecology and potentially lead to new and improved therapies for dysbiosis-related conditions such as BV.

Bacterial vaginosis: A practical review

Bacterial vaginosis is a common vaginal infection that causes discharge, odor, and irritation. It can predispose women to sexually transmitted infections (STIs) including HIV. Recurrent bacterial vaginosis may require prolonged treatment to return the vaginal flora to a normal predominately lactobacilli-dominated environment.

Combined oral and topical antimicrobial therapy for male partners of women with bacterial vaginosis: Acceptability, tolerability and impact on the genital microbiota of couples - A pilot study

Objectives

Recurrence following recommended treatment for bacterial vaginosis is unacceptably high. While the pathogenesis of recurrence is not well understood, recent evidence indicates re-infection from sexual partners is likely to play a role. The aim of this study was to assess the acceptability and tolerability of topical and oral antimicrobial therapy in male partners of women with bacterial vaginosis (BV), and to investigate the impact of dual-partner treatment on the vaginal and penile microbiota.

Methods

Women with symptomatic BV (Nugent Score of 4–10 and ≥3 Amsel criteria) and their regular male sexual partner were recruited from Melbourne Sexual Health Centre, Melbourne, Australia. Women received oral metronidazole 400mg twice daily (or intra-vaginal 2% clindamycin cream, if contraindicated) for 7-days. Male partners received oral metronidazole 400mg twice daily and 2% clindamycin cream topically to the penile skin twice daily for 7-days. Couples provided self-collected genital specimens and completed questionnaires at enrolment and then weekly for 4-weeks. Genital microbiota composition was determined by 16S rRNA gene sequencing. Changes in genital microbiota composition were assessed by Bray-Curtis index. Bacterial diversity was measured by the Shannon Diversity Index.

Results

Twenty-two couples were recruited. Sixteen couples (76%) completed all study procedures. Adherence was high; most participants took >90% of prescribed medication. Medication, and particularly topical clindamycin in males, was well tolerated. Dual-partner treatment had an immediate and sustained effect on the composition of vaginal microbiota (median Bray-Curtis score day 0 versus day 8 = 0.03 [IQR 0–0.15], day 0 vs day 28 = 0.03 [0.02–0.11]). We observed a reduction in bacterial diversity of the vaginal microbiota and a decrease in the prevalence and abundance of BV-associated bacteria following treatment. Treatment had an immediate effect on the composition of the cutaneous penile microbiota (median Bray-Curtis score day 0 vs day 8 = 0.09 [0.04–0.17]), however this was not as pronounced at day 28 (median Bray-Curtis score day 0 vs day 28 = 0.38 [0.11–0.59]). A decrease in the prevalence and abundance of BV-associated bacteria in the cutaneous penile microbiota was observed immediately following treatment at day 8.

Conclusion

Combined oral and topical treatment of male partners of women with BV is acceptable and well tolerated. The combined acceptability and microbiological data presented in this paper supports the need for larger studies with longer follow up to characterize the sustained effect of dual partner treatment on the genital microbiota of couples and assess the impact on BV recurrence.

Antibiotic treatment for the sexual partners of women with bacterial vaginosis

BACKGROUND

Bacterial vaginosis (BV) is an infection that has a prevalence between 10% to 50% worlwide. BV results in an imbalance of the normal vaginal flora. Microorganisms associated with BV have been isolated from the normal flora of the male genital tract, and their presence could be related to the recurrence of BV after antibiotic treatment. Therefore, the treatment of sexual partners could decrease the recurrence of infection and possibly the burden of the disease.

OBJECTIVES

To assess the effectiveness in women and the safety in men of concurrent antibiotic treatment for the sexual partners of women treated for BV.

SEARCH METHODS

We searched the Cochrane Sexually Transmitted Infections Group Specialized Register (23 July 2016), CENTRAL (1991 to 23 July 2016), MEDLINE (1946 to 23 July 2016), Embase (1974 to 23 July 2016), LILACS (1982 to 23 July 2016), the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (23 July 2016), ClinicalTrials.gov (23 July 2016) and the Web of Science™ (2001 to 23 July 2016). We also handsearched conference proceedings, contacted trial authors and reviewed the reference lists of retrieved studies.

SELECTION CRITERIA

Randomized controlled trials (RCTs) that compared the concurrent use of any antibiotic treatment with placebo, no intervention or any other intervention by the sexual partners of women treated for BV.

DATA COLLECTION AND ANALYSIS

Three review authors independently assessed trials for inclusion, extracted data and assessed the risk of bias in the included studies. We resolved any disagreements through consensus. We assessed the quality of the evidence using the GRADE approach.

MAIN RESULTS

Seven RCTs (1026 participants) met our inclusion criteria, and pharmaceutical industry funded four of these trials. Five trials (854 patients) compared any antibiotic treatment of sexual partners with placebo. Based on high quality evidence, antibiotic treatment does not increase the rate of clinical or symptomatic improvement in women during the first week (risk ratio (RR) 0.99, 95% confidence interval (CI) 0.96 to 1.03; 712 participants, four studies; RR 1.06, 95% CI 1.00 to 1.12; 577 patients, three studies, respectively), between the first and fourth week (RR 1.02, 95% CI 0.94 to 1.11; 590 participants, three studies; RR 0.93, 95% CI 0.84 to 1.03; 444 participants, two studies; respectively) or after the fourth week (RR 0.98, 95% CI 0.90 to 1.07; 572 participants, four studies; RR 1.03, 95% CI 0.90 to 1.17; 296 participants, two studies; respectively). Antibiotic treatment does not led to a lower recurrence during the first and fourth week (RR 1.28, 95% CI 0.68 to 2.43; 218 participants, one study; low quality evidence) or after the fourth week of treatment (RR 1.00, 95% CI 0.67 to 1.52; 372 participants, three studies; low quality evidence) in women, but increases the frequency of adverse events (most frequently gastrointestinal symptoms) reported by sexual partners (RR 2.55, 95% CI 1.55 to 4.18; 477 participants, three studies; low quality evidence). Two trials (172 participants) compared any antibiotic treatment for sexual partners with no intervention. When we compared it with no intervention, the effects of antibiotic treatment on recurrence rate after the fourth week (RR 1.71, 95% CI 0.65 to 4.55; 51 participants, one study), clinical improvement between the first and fourth week (RR 0.93, 95% CI 0.70 to 1.25; 152 participants, two studies) and symptomatic improvement after the fourth week (RR 0.66, 95% CI 0.39 to 1.11; 70 participants, one study) were imprecise and there were no differences between groups. We downgraded the quality of the evidence to low or very low.

AUTHORS' CONCLUSIONS

High quality evidence shows that antibiotic treatment for sexual partners of women with BV, compared with placebo, does not increase the rate of clinical or symptomatic improvement during the first, between the first and fourth or after the fourth week into the women. Low quality evidence suggests that antibiotic treatment does not led to a lower recurrence rate during the first and fourth or after the fourth week of treatment into the women, but increases the frequency of adverse events reported by sexual partners. Finally, compared with no intervention, antibiotic treatment does not decrease the recurrence rate after the fourth week and does not increase the frequency of clinical or symptomatic improvement between the first and fourth or after the fourth week into the women, respectively.

Penile Microbiota and Female Partner Bacterial Vaginosis in Rakai, Uganda

Bacterial vaginosis (BV) is a common vaginal bacterial imbalance associated with risk for HIV and poor gynecologic and obstetric outcomes. Male circumcision reduces BV-associated bacteria on the penis and decreases BV in female partners, but the link between penile microbiota and female partner BV is not well understood. We tested the hypothesis that having a female partner with BV increases BV-associated bacteria in uncircumcised men. We characterized penile microbiota composition and density (i.e., the quantity of bacteria per swab) by broad-coverage 16S rRNA gene-based sequencing and quantitative PCR (qPCR) in 165 uncircumcised men from Rakai, Uganda. Associations between penile community state types (CSTs) and female partner's Nugent score were assessed. We found seven distinct penile CSTs of increasing density (CST1 to 7). CST1 to 3 and CST4 to 7 were the two major CST groups. CST4 to 7 had higher prevalence and abundance of BV-associated bacteria, such as Mobiluncus and Dialister, than CST1 to 3. Men with CST4 to 7 were significantly more likely to have a female partner with a high Nugent score (P = 0.03). Men with two or more extramarital partners were significantly more likely to have CST4 to 7 than men with only marital partners (CST4 to 7 prevalence ratio, 1.84; 95% confidence interval [CI], 1.16 to 2.92). Female partner Nugent BV is significantly associated with penile microbiota. Our data support the exchange of BV-associated bacteria through intercourse, which may explain BV recurrence and persistence.

IMPORTANCE

Bacterial vaginosis (BV) is sexually associated but not considered a sexually transmitted disease. Our findings suggest that the uncircumcised penis is an important niche for BV-associated genital anaerobes. In addition, we found a link between extramarital sexual relationships and BV-associated bacteria in men, which parallels earlier findings of the association between sexual activity and BV in women. This suggests the sexual transmissibility of BV-associated bacteria. Reducing bacterial exchange by barrier methods and managing carriage of BV-associated bacteria in men may decrease BV persistence and recurrence in women.

Genital infections and syndromic diagnosis among HIV-infected women in HIV care programmes in Kenya

Control of genital infections remains challenging in most regions. Despite advocacy by the World Health Organization for syndromic case management, there are limited data on the syndromic approach, especially in HIV care settings. This study compared the syndromic approach with laboratory diagnosis among women in HIV care in Kenya. A mobile team visited 39 large HIV care programmes in Kenya and enrolled participants using population-proportionate sampling. Participants provided behavioural and clinical data with genital and blood specimens for lab testing. Among 1063 women, 68.4% had been on antiretroviral therapy >1 year; 58.9% were using cotrimoxazole prophylaxis; 51 % had CD4+T-lymphocytes < 350 cells/µL. Most women (63.1%) reported at least one genital symptom. Clinical signs were found in 63% of women; and 30.8% had an aetiological diagnosis. Bacterial vaginosis (17.4%), vaginal candidiasis (10.6%) and trichomoniasis (10.5%) were the most common diagnoses. Using laboratory diagnoses as gold standard, sensitivity and positive predictive value of the syndromic diagnosis for vaginal discharge were 47.6% and 52.7%, respectively, indicating a substantial amount of overtreatment. A systematic physical examination increased by 9.3% the positive predictive value for genital ulcer disease. Women attending HIV care programmes in Kenya have high rates of vaginal infections. Syndromic diagnosis was a poor predictor of those infections.

Hormonal contraception is associated with a reduced risk of bacterial vaginosis: a systematic review and meta-analysis

Objective

To examine the association between hormonal contraception (HC) and bacterial vaginosis (BV) by systematic review and meta-analysis.

Methods

Medline, Web of Science and Embase databases were searched to 24/1/13 and duplicate references removed. Inclusion criteria 1) >20 BV cases; 2) accepted BV diagnostic method; 3) measure of HC-use either as combined oestrogen-progesterone HC (combined), progesterone-only contraception (POC) or unspecified HC (u-HC); 4) ≥10% of women using HC; 5) analysis of the association between BV and HC-use presented; 6) appropriate control group. Data extracted included: type of HC, BV diagnostic method and outcome (prevalent, incident, recurrent), and geographical and clinic-setting. Meta-analyses were conducted to calculate pooled effect sizes (ES), stratified by HC-type and BV outcome. This systematic review is registered with PROSPERO (CRD42013003699).

Results

Of 1713 unique references identified, 502 full-text articles were assessed for eligibility and 55 studies met inclusion criteria. Hormonal contraceptive use was associated with a significant reduction in the odds of prevalent BV (pooled effect size by random-effects [reES] = 0.68, 95%CI0.63–0.73), and in the relative risk (RR) of incident (reES = 0.82, 95%CI:0.72–0.92), and recurrent (reES = 0.69, 95%CI:0.59–0.91) BV. When stratified by HC-type, combined-HC and POC were both associated with decreased prevalence of BV and risk of incident BV. In the pooled analysis of the effect of HC-use on the composite outcome of prevalent/incident/recurrent BV, HC-use was associated with a reduced risk of any BV (reES = 0.78, 95%CI:0.74–0.82).

Conclusion

HC-use was associated with a significantly reduced risk of BV. This negative association was robust and present regardless of HC-type and evident across all three BV outcome measures. When stratified by HC-type, combined-HC and POC were both individually associated with a reduction in the prevalence and incidence of BV. This meta-analysis provides compelling evidence that HC-use influences a woman’s risk of BV, with important implications for clinicians and researchers in the field.

Bacterial vaginosis (BV) candidate bacteria: associations with BV and behavioural practices in sexually-experienced and inexperienced women

Background

In recent years several new fastidious bacteria have been identified that display a high specificity for BV; however no previous studies have comprehensively assessed the behavioural risk associations of these bacterial vaginosis-candidate organisms (BV-COs).

Methods

We examined the associations between 8 key previously described BV-COs and BV status established by Nugent's score (NS). We also examined the sexual practices associated with each BV-CO. We incorporated 2 study populations: 193 from a sexually-inexperienced university population and 146 from a highly sexually-active clinic population. Detailed behavioural data was collected by questionnaire and vaginal smears were scored by the Nugent method. Stored samples were tested by quantitative PCR assays for the 8 BV-COs: Atopobium vaginae, Gardnerella vaginalis, Leptotrichia spp., Megasphaera type I, Sneathia spp., and the Clostridia-like bacteria BVAB1, BVAB2 and BVAB3. Associations between BV-COs and BV and behaviours were examined by univariate and multivariable analyses.

Results

On univariate analysis, all BV-COs were more common in BV compared to normal flora. However, only Megasphaera type I, BVAB2, A. vaginae and G. vaginalis were significantly independently associated with BV by multivariable analysis. Six of the eight BV-COs (Megasphaera type I, BVAB2, BVAB3, Sneathia, Leptotrichia and G. vaginalis) were rare or absent in sexually-unexposed women, and demonstrated increasing odds of detection with increasing levels of sexual activity and/or numbers of lifetime sexual partners. Only G. vaginalis and A. vaginae were commonly detected in sexually-unexposed women. Megasphaera type I was independently associated with women-who-have-sex-with women (WSW) and lifetime sexual partner numbers, while unprotected penile-vaginal-sex was associated with BVAB2 detection by multivariate analysis.

Conclusions

Four of eight key BV-COs were significantly associated with BV after adjusting for the presence of other BV-COs. The majority of BV-COs were absent or rare in sexually-unexposed women, and associated with increasing sexual exposure, suggesting potential sexual transmission of BV-COs.

Bacterial vaginosis associated with increased risk of female-to-male HIV-1 transmission: a prospective cohort analysis among African couples

BACKGROUND

Bacterial vaginosis (BV), a disruption of the normal vaginal flora, has been associated with a 60% increased risk of HIV-1 acquisition in women and higher concentration of HIV-1 RNA in the genital tract of HIV-1-infected women. However, whether BV, which is present in up to half of African HIV-1-infected women, is associated with an increase in HIV-1 transmission to male partners has not been assessed in previous studies.

METHODS AND FINDINGS

We assessed the association between BV on female-to-male HIV-1 transmission risk in a prospective study of 2,236 HIV-1-seropositive women and their HIV-1 uninfected male partners from seven African countries from a randomized placebo-controlled trial that enrolled heterosexual African adults who were seropositive for both HIV-1 and herpes simplex virus (HSV)-2, and their HIV-1-seronegative partners. Participants were followed for up to 24 months; every three months, vaginal swabs were obtained from female partners for Gram stain and male partners were tested for HIV-1. BV and normal vaginal flora were defined as a Nugent score of 7-10 and 0-3, respectively. To reduce misclassification, HIV-1 sequence analysis of viruses from seroconverters and their partners was performed to determine linkage of HIV-1 transmissions. Overall, 50 incident HIV-1 infections occurred in men in which the HIV-1-infected female partner had an evaluable vaginal Gram stain. HIV-1 incidence in men whose HIV-1-infected female partners had BV was 2.91 versus 0.76 per 100 person-years in men whose female partners had normal vaginal flora (hazard ratio 3.62, 95% CI 1.74-7.52). After controlling for sociodemographic factors, sexual behavior, male circumcision, sexually transmitted infections, pregnancy, and plasma HIV-1 RNA levels in female partners, BV was associated with a greater than 3-fold increased risk of female-to-male HIV-1 transmission (adjusted hazard ratio 3.17, 95% CI 1.37-7.33).

CONCLUSIONS

This study identified an association between BV and increased risk of HIV-1 transmission to male partners. Several limitations may affect the generalizability of our results including: all participants underwent couples HIV counseling and testing and enrolled in an HIV-1 prevention trial, and index participants had a baseline CD4 count ≥ 250 cells/mm³ and were HSV-2 seropositive. Given the high prevalence of BV and the association of BV with increased risk of both female HIV-1 acquisition and transmission found in our study, if this association proves to be causal, BV could be responsible for a substantial proportion of new HIV-1 infections in Africa. Normalization of vaginal flora in HIV-1-infected women could mitigate female-to-male HIV-1 transmission.

TRIAL REGISTRATION

ClinicalTrials.com NCT00194519.