Jan. 16 (HealthDay News) -- Sexually active gay men are much more likely than others to be infected by a highly resistant strain of staph bacteria, warns a study led by researchers at the University of California, San Francisco (UCSF).

The scientists analyzed patient medical charts and found that sexually active gay men in San Francisco are about 13 time more likely to be infected with multidrug-resistant, community-associated MRSA bacteria than people in the general population.

Overall, about one in 3,800 people in San Francisco is infected with this very potent strain of MRSA.

The findings were published in the Jan. 14 early online edition of the Annals of Internal Medicine.

"These multi-drug resistant infections often affect gay men at body sites in which skin-to-skin contact occurs during sexual activities," lead author Binh Diep, a UCSF postdoctoral scientist at San Francisco General Hospital Medical Center, said in a prepared statement.

"But because the bacteria can be spread by more casual contact, we are also very concerned about a potential spread of this strain into the general population," Diep said.

MRSA invades skin and tissue beneath the skin, causing abscesses and ulcerations that can turn into life-threatening infections. In people who become infected, prompt diagnosis and treatment are crucial.

Diep said a thorough scrubbing with soap and water may be the most effective way to prevent skin-to-skin transmission, especially after sex.

SOURCE: University of California, San Francisco, news release, Jan. 14, 2008