16 February 2009

MRSA at the beach

Am I the only person whose grandmother said it was healthy to swim in the sea because the salt would disinfect any cuts or skin nastinesses? Well, apparently my grandmother — and who knows, maybe yours too — was wrong:

The annual meeting of the American Association for the Advancement of Science concluded today in Chicago. Among the presentations: Physicians at the University of Miami tested seawater at popular Florida beaches and found that swimmers have a 37% chance of coming into contact with drug-sensitive staph, and 3% chance of encountering MRSA. The organisms are deposited into the water by infected or colonized humans.

Dr. Lisa Pisano said in a precis distributed to press for the meeting (I don't think I am able to link to this, but am checking):
Our hypothesis is that the bathers using recreational waters not only contribute to the organisms in the water, and therefore serve as a source of staph, but they might also become colonized or infected by the organisms that they are exposed to while in the water or on the beaches. Investigators from our team had previously shown that staph was shed by adults into marine water filled pools after short exposures, supporting that people could serve as a source for the bacteria. In the studies I will present, we confirm that adults who are known to be colonized indeed shed their own bacteria into marine waters. We also show that children, in diapers, both known and some not known to be colonized with staph also shed bacterial into marine waters.
37% of the water samples contained staph and 3% of these were MRSA. Genetic analyses of the isolated organisms revealed that the majority of the staph, not MRSA, appeared to be non-aggressive strains lacking the key virulence factors known to be associated with more aggressive strains of bacteria. However the majority of the isolated MRSA were those likely to of the more aggressive variety.
To prevent colonization, or infection of any abrasions or open wounds, the researchers recommend showering before entering the water and before leaving the beach.

Until I figure out what of the materials can be linked to, or whether press releases were put online by funders of the research, here's a Reuters story carried by ScientificAmerican.com.

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