IU researchers discover a common bacterial infection can be sexually transmitted
IU School of Medicine Mar 22, 2023
INDIANAPOLIS—Researchers from Indiana University School of Medicine have made a major discovery about a common vaginal infection, finding the bacteria that causes it can also have a major presence in men and can be sexually transmitted.
“We looked at the urethral microbiome of healthy adult men and found that many of them actually had bacteria that is associated with bacterial vaginosis in women,” said David Nelson, PhD, professor of microbiology and immunology at IU School of Medicine and co-corresponding author of the study. “These bacteria can be transmitted through heterosexual, vaginal sex, something that has never been shown in research before.”
Bacterial vaginosis is a common condition in women, but until now, researchers have not confirmed it can be transmitted via sex. Nelson said, many scientists previously thought urine is sterile. But this new study, published recently in Cell Reports Medicine, proves that is not the case. The team looked at 110 distal urethral swab specimens from men with no urogenital symptoms, no sexually transmitted infections (STIs) and no inflammation of the urethra.
“What we found was stunning,” Nelson said. “These men had two types of colonized bacteria—one that was native to the penile urethra, and one that was from an outside source. This is the first time it has been shown that the human microbiome is primarily shaped by behavior.”
Researchers found only the men who reported having vaginal sex carried the bacteria often associated with bacterial vaginosis. They also discovered the bacteria was detectable for at least two months after having vaginal sex.
Nelson said the discovery could lead to sweeping changes in how men and women are treated for certain STIs, including bacterial vaginosis, by doing more contact tracing to treat sexual partners better.
"Our research provides the first healthy baseline for clinicians and scientists to compare with diseased urogenital states,” said Evelyn Toh, PhD, assistant research professor of microbiology and immunology and lead author of the paper. “Having established this baseline, we may be able to offer new insights into bacteria’s role in urogenital diseases. There is still stigma in talking about sex, and hence STIs are often overlooked. However, STIs really impact women and minorities disproportionately, as well as socioeconomically disadvantaged people.”
While this study shows women can transmit bacterial vaginosis to men, they’re now studying whether men could transmit it to women as well.
The study was done in collaboration with researchers at the University of Alabama—Birmingham and Loyola University Chicago. Other study authors from IU School of Medicine include Stephen Jordan, MD, PhD; Teresa Batteiger, MD, MS; Netsanet Gebragziabher; James A. Williams; Lora Fortenberry; and J. Dennis Fortenberry, MD, MS.
About IU School of Medicine
IU School of Medicine is the largest medical school in the U.S. and is annually ranked among the top medical schools in the nation by U.S. News & World Report. The school offers high-quality medical education, access to leading medical research and rich campus life in nine Indiana cities, including rural and urban locations consistently recognized for livability.