10.16.07

MRSA: from hospital pathogen to community scourge

MRSA is biologist shorthand for Methicillin-Resistant Staphylococcus aureus. S. aureus is a bacterium that's carried by approximately a third of us--we provide it safe harbor typically either on our skin, or in our nose. Most of the time it's just another one of the many trillions of bacteria we all share our environment with; however, sometimes this cohabitation can become deadly--and the likelihood of this happening increases when you carry a strain of staph that is resistant to most of the antibiotics available to treat it, as an estimated 2.3 million Americans do.

Staph bacteria cause a variety of types of infections. They can result in mild skin infections, such as boils and cellulitis. They occasionally cause food poisoning or pneumonia. But it's when they enter your bloodstream that they're at their worst, causing potentially fatal illnesses such as toxic shock syndrome. With ordinary staph, these can often be treated with antibiotics. However, resistance to a variety of antibiotics is present in Staph--most notably resistance to methicillin. This antibiotic was introduced in 1959, and resistance to the drug was reported a scant 2 years later. However, in the intervening years, much of that resistance was confined to hospital settings: healthy people who were able to steer clear of the hospital were unlikely to become infected with this pathogen.

No more.

In the past few years, a strain called CA-MRSA has emerged: the "CA" stands for "community acquired." This means that, rather than encountering MRSA in a medical setting, the bacterium is picked up from your neighborhood: your school, or place of employment, or your gym (as has been the case in several outbreaks). Indeed, athletes are a new risk group: a recent news story shows that a Virginia high school had to close and disinfect its weight room, and even professional football teams have been hit by the bacterium. Even a muscled linebacker isn't a match for this tiny organism; indeed, during a 2003 MRSA outbreak amongst the St. Louis Rams, linebackers were at a high risk of acquiring the infection. High school sports teams have also been affected, and in some cases, tragically so. These community-acquired MRSA can also complicate other infections, leading to a deadly synergy; this is exemplified by the death of three children from influenza complicated by MRSA infections.

The bacterium has even spread to horses, pigs, and dogs and cats--a big change in the epidemiology of the organism from just a decade or so ago.

Right now, there's no vaccine for MRSA, and our treatment options are becoming ever more slim. Like many infectious diseases, it's best to keep in mind the "ounce of prevention" adage, and do all you can to protect yourself before something nasty develops. Wash your hands, don't share dirty towels, disinfect machines you use at the gym, and just do what you can to keep your bacteria to yourself.

[Edited to add: just out today is a story showing that there are about 100,000 cases of MRSA yearly in the U.S. Much more info at the link.]

Tags: bacteria, MRSA, sports teams, Staphylococcus

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