Health officials are tracking a new type of infection with Staphylococcus aureus that is resistant to even more antibiotics than MRSA, the drug-resistant staph that has spread from coast to coast over the past seven years. (MRSA stands for "methicillin-resistant Staphylococcus aureus".)
So far, nearly all recognized cases of the multiply drug resistant staph have been among gay and bisexual men. The cases are showing up most often in San Francisco, Los Angeles and New York.
Boston is also an epicenter of the new MDR staph. The city's Fenway Community Health Center, which serves many gay men, first began noticing cases of unusually resistant staph infections about six years ago.
"We initially saw just a few sporadic cases," says Dr. Steve Boswell, the clinic's president and CEO. "But over a period of 18 to 24 months, the number of cases climbed significantly."
Currently one or two cases show up at the Fenway Center each week, Boswell says.
The infection ranges from mild to very serious. Across the country, a few men have even died.
MDR staph is related to an MRSA strain called USA-300 that has appeared in schools, prisons and athletic teams around the country. But MDR staph is even more resistant to antibiotics.
Ordinary resistant USA-300 staph can escape being killed by methicillin and other penicillin antibiotics. The new MDR type also resists treatment by clindamycin, which is often recommended to treat resistant staph. It's also resistant to erythromycin and to mupirocin, a topical antibiotic that's used to kill lurking staph on the skin to prevent recurrent infections.
Ominously, the new MDR variant has in some cases shown it can develop resistance to even more stand-by antibiotics, such as vancomycin and Bactrim. That would leave doctors with perilously few, and costly, alternatives.
Boswell says the new variant also causes more-virulent skin infections.
"They grow much more rapidly," he says. "Hours can make a difference."
But because doctors often try ineffective antibiotics first, precious time is lost.
"That delay, which can often be days and in some cases even weeks, can result in significant compromises of the patient — in some cases even death," Boswell says.
An article in the online version of the Annals of Internal Medicine documents the spread of MDR staph. Its first author, epidemiologist Binh An Diep, says the bacterium has made striking inroads in some communities.
Among gay men with resistant staph infections, Diep says, about 20 percent in San Francisco and up to 50 percent in Boston "are infected with this more-difficult-to-treat form of USA-300."
Incidence of the new variant is 13 times higher in San Francisco's heavily gay Castro neighborhood and surrounding zip codes than in the city's general population.
That concentration — and the fact that many infections appear on the buttocks and the genital region — is leading researchers to suggest that MDR staph is being spread through sexual contact. That leads some to worry this new infection could stigmatize gay men once again.
"We are worried about the fact that this could be taken to mean that this is another gay man plague," Diep says. "This is really not what we want to push forth here. I think there's a message of hope — that just soap and water is the best defense against community-acquired MRSA infection."
Even so, experience suggests the MDR staph won't stay confined to the gay community.
"Because USA-300 and other Staph aureus are so easily spread — just through [skin-to-skin] contact transmission — we don't think it will be restricted to the men-who-have-sex-with-men population, but will be spread into the general population," Diep says.
Already, researchers have found the new variant in an 81-year-old woman in New York City.
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