New Super Strength USA300 has been spreading since 2003

Link: S.F. gay community an epicenter for new strain of virulent staph.

But the latest problem is being caused by a new variant of USA300 that was first detected in a San Francisco patient in 2003. Among the six antibiotics it is resistant to are three that are normally considered for treatment of suspected MRSA. The study estimated that 200 cases of this highly drug-resistant variant are turning up in San Francisco each year, mostly among gay men. "We are nowhere near the peak," Diep said. "The peak will occur when it spreads into the general population."

The new variant of USA300 is resistant to the antibiotics erythromycin, clindamycin, tetracycline, Cipro-like antibiotics and drugs in the penicillin family. It also does not respond to mupirocin - a gel that is often used to kill MRSA growing in people's noses.

That still leaves a variety of antibiotics that will kill the new USA300 strain, but they tend to be more expensive and require intravenous drips. One common oral antibiotic, Bactrim, is still effective against it.

Chambers also pointed out that researchers at San Francisco General have shown that many skin sores and boils caused even by these drug-resistant strains of staph often can be treated without any antibiotics, just by surgical drainage of pus.

One of the paradoxes of bacterial infections is that using antibiotics to treat them is one of the quickest ways to promote antibiotic resistance. Although the drugs sometimes are essential, overuse is weakening their effectiveness worldwide.