BALTIMORE, Jan. 6 (UPI) -- Circumcision, which lowers HIV risk in men, also dramatically changes the bacterial communities of the penis, U.S. researchers found.
Scientists at the Translational Genomics Research Institute and Johns Hopkins University said the bacterial changes may be associated with earlier observations that women whose male partners are circumcised are less likely to develop bacterial vaginosis, an imbalance between good and harmful bacteria.
The study was part of a larger effort by the U.S. National Institutes of Health to study and describe the "human microbiome" -- the microbes that exist collectively on and in the human body.
The study, published in the journal PLoS ONE, found that circumcision eliminates an area of mucous membrane and dramatically changes the penile bacterial ecosystem. The analysis of more than 40 types of bacteria suggests the introduction of more oxygen following circumcision decreases the presence of anaerobic -- non-oxygen -- bacteria and increases the amount of aerobic -- oxygen-required -- bacteria.
"This study clearly shows that male circumcision markedly reduces genital colonization with anaerobic bacteria in men,'' senior author Dr. Ronald H. Gray, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health, says in a statement.
"These bacteria, which cannot grow in the presence of oxygen, have been implicated in inflammation and a number of infections affecting both men and women. Our randomized trials have shown that male circumcision prevents HIV infection in men and protects their female partners from vaginal infections, especially bacterial vaginosis."