Bacterial Vaginosis in Women
Bacterial vaginosis (BV) is one of the most common infections in women. Symptoms of BV may include a watery, white or grey discharge instead of normal vaginal secretions, and a strong or unusual odor from the vagina, often described as a 'fishy' odor. The condition is characterized by a shift in the composition of vaginal microbial communities from the normal healthy bacteria - in particular lactic acid-producing lactobacilli - which become replaced by an overgrowth of various other bacteria, notably strict anaerobes, and an elevation in vaginal pH (i.e., an increase in alkalinity of the vaginal fluid).
Bacterial vaginosis is sexually transmitted, as shown by an Australian meta-analysis [Fethers et al., 2008]. This systematic review and meta-analysis showed that the epidemiology of bacterial vaginosis appeared to be similar to that of established STIs [Fethers et al., 2008].
A longitudinal study in Pittsburg of 773 women without BV at enrolment found that over one year, those whose partners were uncircumcised were twice as likely to have BV [Cherpes et al., 2008]. Two small US studies, thus having limited power, were unable to find an association, however [Zenilman et al.; Schwebke & Desmond, 2005; Mehta et al., 2022]. The 'gold standard' in epidemiology is, nevertheless, the randomized controlled trial, and one of these, in Uganda, found that bacterial vaginosis of any type was 40% lower, and severe bacterial vaginosis was 61% lower in the wives of men in the circumcised arm of the trial [Gray et al., 2009a].
The foreskin of males could facilitate survival of BV organisms, such as gram-negative anerobic bacteria, and make an uncircumcised male amore efficient and more prolonged transmitter of infection [Fethers et al., 2008; Gray et al., 2009a]. The much higher prevalence of such anaerobic bacteria under the foreskin of men prior to circumcision was established in an analysis of the microbiome of men from a large randomized controlled trial, and the authors highlighted the fact that these have been associated with bacterial vaginosis [Tobian et al., 2010]. The penile microbiota of uncircumcised men is considered to be a sexually transmitted infection during intercourse, triggering Bacterial vaginosis in women [Liu et al., 2015]. A 12-month prospective cohort study of 168 couple in which the women did not have bacterial vaginosis at baseline found an incidence of 37% in the women if the man was uncircumcised and 26% if the man was circumcised [Mehta et al., 2020]. The top 10 most predictive taxa in the penile glans/coronal sulcus microbiome that were associated with Bacterial vaginosis in the vagina, were Parvimonas, Lactobacillus iners, L. crispatus, Dialister, Sneathia sanguinegens, and Gardnerella vaginalis [Mehta et al., 2020]. The study concluded that that concordance of penile microbiome with the vaginal microbiome of sex partners is not merely reflecting the vaginal microbiome but can contribute to it. A review linked the penile microbiota of uncircumcised men to HIV and HPV infection [Onywera et al., 2020], as well as HSV-2 infection [Mehta et al., 2022].
Bacterial vaginosis is associated with cervical intraepithelial neoplasia, the precurser to cervical cancer [Nam et al., 2009].
For more see systematic reviews [Grund et al., 2017; Morris et al., 2019b].
