Circumcision drastically alters the microbiome of the penis, changes that could explain why circumcision offers protection against HIV and other viral infections. In a study to be published on April 16 in mBio, the online open-access journal of the American Society for Microbiology, researchers studied the effects of adult male circumcision on the types of bacteria that live under the foreskin before and after circumcision. By one year post-procedure, the total bacterial load in that area had dropped significantly and the prevalence of anaerobic bacteria, which thrive in locations with limited oxygen, declined while the numbers of some aerobic bacteria increased slightly.
"The change in the communities is really characterized by the loss of anaerobes. It's dramatic," says the corresponding author, Lance Price of the Translational Genomics Research Institute (TGen) in Flagstaff, Arizona and George Washington University in Washington, DC. "From an ecological perspective, it's like rolling back a rock and seeing the ecosystem change. You remove the foreskin and you're increasing the amount of oxygen, decreasing the moisture - we're changing the ecosystem," he continues.
Randomized controlled trials show that circumcision reduces the risk of HIV infection in men by 50-60% and reduces the risk of infection with human papillomavirus and herpes simplex virus type 2, but the biology behind these benefits is not well understood. It could be that the anatomy of the circumcised penis helps prevent infection, or it could be that changes in the microbiome confer protection, or some combination of the two.
Using swab samples from a large circumcision trial in Uganda, Price and his colleagues at Johns Hopkins and TGen set out to determine whether circumcision significantly alters the penis microbial community. Using a quantitative technique called qPCR along with pyrosequencing to identify individual community members, the researchers compa
|Contact: Jim Sliwa|
American Society for Microbiology