Taking birth control pills may make women's bodies more hospitable to staph bacteria, a new study from Germany suggests. In the study, women takinghormonal contraceptionwere about twice as likely to persistently harbor staph bacteria in their nasal passages compared with women not taking hormonal contraception. The findings suggest that the widespread use of birth control increases the "pool" of people harboring the bacteria, which in turn, may contribute to its spread to people susceptible to getting sick from an infection, said study researcher Dennis Nurjadi, of the Institute for Tropical Medicine in Tübingen. The women in the study did not havestaph infections. Many people carry the bacteria, calledStaphylococcus aureus, on their skin or in their nasal passages without any problems. However, the bacteria can cause skin infections, particularly inside cuts and scratches, and infections can be lethal if they enter the bloodstream, according to the Mayo Clinic. People with weakened immune systems are particularly susceptible to staph infections. The study only found an association, and not a direct cause-effect link between taking birth control and harboring staph. But if the findings hold up in future studies, it would mean that about 20 percent of women who carry the bacteria do so because they use hormonal contraception, the researchers said. The study was published Sept. 5 in the journal Clinical Infectious Diseases. Nurjadi and colleagues analyzed information from 1,180 young men and women who were seeking health advice before traveling to subtropical regions and provided two nasal swabs at least a month apart. About 22 percent of participants carriedStaphylococcus aureusin their nasal passages on both occasions, and were considered "persistent" carriers. Women who took hormonal contraception were 1.9 times more likely to be persistent carriers compared with women who did not take hormonal contraception. Additionally, the study showed that men were more likely to carry the bacteria than women who were not taking contraception. However, women taking contraception were more likely to carry the bacteria than men. The findings held after the researchers took into account factors that could affect the likelihood of carrying the bacteria, including age, animal contact, smoking habits and history of skin infections. Previous studies have found women with high estrogen levels are more likely to carryStaphylococcus aureuscompared with women who have lower levels. It could be that high hormone levels affect the immune system, and in turn, make women more prone to carrying the bacteria, the researchers said. A study published last year found women in Africa whoused hormonal contraception were at increased risk of acquiring HIV.