Strain of Drug-Resistant Staph Emerging in San Francisco, Study Finds

A drug-resistant strain of methicillin-resistant staphylococcus aureus, or MRSA, is appearing among men who have sex with men in San Francisco and Boston, according to a study published online in the journal Annals of Internal Medicine, the New York Times reports (Altman, New York Times, 1/15).

For the study, Binh Diep, a researcher at UC-San Francisco, and colleagues reviewed the charts of 183 people treated for MRSA at the San Francisco General Hospital's Positive Health Program, an outpatient program for HIV-positive people. They also reviewed the charts of an additional 130 people at Fenway Community Health clinic in Boston (Wall Street Journal, 1/15).

According to a statistical analysis based on ZIP codes, one in 588 people in San Francisco's Castro neighborhood, which has a large MSM population, is living with MRSA, compared with one in 3,800 people across San Francisco. The study also found that MSM in San Francisco were 13 times more likely than other city residents to contract MRSA (New York Times, 1/15).

Francoise Perdreau-Remington -- director of the molecular epidemiology lab at SFGH, where the strain was first identified -- said the strain has been found in 44 states and is beginning to spread through Europe (Russell, San Francisco Chronicle, 1/15).

The review found that MSM ages 18 to 35 were the most likely to have the infection (Chase, Wall Street Journal, 1/15). HIV-positive people "seem especially prone" to the infection, according to the Chronicle (San Francisco Chronicle, 1/15).

The study found MRSA spreads most often through anal intercourse but also can be spread through casual skin-to-skin contact or by touching contaminated surfaces. The most effective way to prevent skin-to-skin transmission of MRSA is to wash with soap and water, particularly after sex, the researchers said (New York Times, 1/15).

According to the Chronicle, the strain, called USA300, is resistant to six major antibiotic classes (San Francisco Chronicle, 1/15). USA300 is resistant to two of the three alternative MRSA treatments recommended by CDC and the Infectious Diseases Society of America.

Henry Chambers, a study author and chief of infectious diseases at SFGH, said that the strain also is resistant to mupirocin, which has been "advocated for eradicating the strain from carriers" (New York Times, 1/15).

USA300 is "more virulent than standard staph," Shelly Gordon, an infectious disease specialist at California Pacific Medical Center in San Francisco, said. She added that emergency department physicians should test for drug resistance to avoid using the wrong antibiotic and fueling further resistance (Wall Street Journal, 1/15).

Diep added that "once" the strain "reaches the general population, it will be truly unstoppable. That's why we're trying to spread the message of prevention."

Chambers said that high antibiotic use is the "most important factor" that the new drug-resistant strain is appearing among MSM (Wall Street Journal, 1/15).

NPR's "All Things Considered" on Monday reported on the study. The segment includes comments from Steve Boswell, president and CEO of the Fenway Community Health Clinic, and Diep (Knox, "All Things Considered," NPR, 1/14).

Audio and a partial transcript of the segment, as well as expanded NPR coverage, are available online.

KQED's "Forum" on Wednesday was scheduled to include a discussion about the study. Scheduled guests included:

• Chambers;
• Diep; and
• Sabin Russell, medical reporter for the Chronicle ("Forum" Web site, 1/16).