Certain Penis-Dwelling Bacteria Might Increase Your HIV Risk

By Ryan F. Mandelbaum on at

HIV transmission is a complex process with factors beyond just who you sleep with and how. The virus ultimately needs to find its way to the correct kinds of cells in order to wreak havoc. And some of the risk, at least for those with penises, may come from the kinds of bacteria on the tip.

A team of researchers analysed the bacteria living on patients’ foreskins in Uganda, and they found higher levels of certain kinds of bacteria on patients who remained HIV negative versus those who contracted HIV during the course of another study. The scientists think that controlling specific bacteria on the penis, perhaps with an antimicrobial that targets them, could help reduce the risk of HIV infection.

The samples came from a trial performed from 2004 to 2006 and included 182 uncircumcised patients, of which 46 became infected with HIV and 136 did not. All subjects had roughly the same amount of bacteria on their penises, but those who ended up acquiring HIV had higher abundances of the kinds of bacteria that don’t need oxygen to survive (called “anaerobes”), including Prevotella, Dialister, Mobiluncus and Murdochiella, according to the study published today in the journal mBio.

The researchers have a guess as to what caused individuals with certain anaerobic bacteria to contract HIV: An increase in white blood cell-attracting molecules produced by cells in the foreskin. Those molecules could specifically attract the kinds of white blood cells most susceptible to an HIV infection. “Thus, the response of the immune system to shifts in the penile microbiome may facilitate productive infection by HIV,” the authors write in the study. These bacteria might, in other words, be altering the immune system’s behavior to promote an HIV infection.

Obviously, this is just an association presented by a single study, but it adds an important detail to a bigger picture. Yes, current treatments can reduce a patient’s chance of transmitting the disease to almost zero, according to CNN. This new paper points to new strategies to help those who might not have access to the treatments—the popular prevention treatments PrEP remains unavailable in some areas in Africa, for example. Additionally, past research has already shown that male circumcision reduces a patient’s chance of acquiring HIV.

At least one researcher not involved with the study spoke positively about its results. “This is an important study that helps to try to understand the risk of uncircumcised men of acquiring HIV,” Carlos Del Rio, Chair of the Department of Global Health at the Rollins School of Public Health at Emory University, told Gizmodo in an email. “It seems like the higher presence of anaerobes in the penile microbiome significantly increases the risk.”

I’ve reached out to the study’s authors to determine what comes next. But if these study’s results hold, it’s possible that certain antimicrobial treatments could help, alongside other treatments to reduce the risk that these genital bacteria might pose. [mBio]


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