Research Strengthens Case for Sexual Transmission of Bacteria Linked to HIV Risk

Professor Lance Price of the Milken Institute School of Public Health’s Department of Environmental and Occupational Health is a senior author of new research published in mBio which supports the theory that bacterial vaginosis (BV) can be sexually transmitted.  BV is a common vaginal ecological imbalance associated with increased risk for HIV and pregnancy complications. BV affects women of all ethnic groups, but it is seen in up to 50 percent of women of African ancestry.  

Price and his collaborators at the Johns Hopkins School of Medicine, the Rakai Health Sciences Program at the Johns Hopkins Bloomberg School of Public Health, and Translational Genomics Research Institute (TGen) evaluated samples from 165 uncircumcised men from a rural area in Uganda, a country where 7.4 percent of the population aged 15 to 49 has HIV, according to the United Nations AIDS Secretariat. Whether BV is transmissible through sexual activity remains controversial, despite studies showing that medical male circumcision both reduces BV-associated bacteria on the penis and decreases BV in female partners. The research project explored whether a detectable difference exists between the penile microbiota of men whose female partner did or did not have BV. 

The so-called penile microbiota represents the full scope of bacteria found on the penis. The researchers categorized the uncircumcised men based on the composition of their penile microbiota. Their analysis suggests that the uncircumcised penis may serve as a reservoir for bacteria associated with BV, since BV-associated bacteria are common in all uncircumcised men and are significantly elevated in men whose female partner has BV. The researchers also found a link between extra-marital sexual relationships and bacteria associated with BV.  These findings support the hypothesis that BV could be sexually transmitted, Price says.  In addition to his position at Milken Institute SPH, Price is also the Director of the TGen Center for Microbiomics and Human Health.

“Our research suggests that an ecological imbalance may be just as transmissible as the single pathogens that cause classic sexually transmitted infections, such as Chlamydia or Syphilis,” says Cindy Liu, House Staff in the Department Pathology at the Johns Hopkins School of Medicine and lead author of the study. “If we want to prevent or reduce BV, we will need to pay more attention to the role of sexual transmission and look at the big picture.”  BV, which often goes undetected, can increase a woman’s risk for sexually transmitted disease, she says.