Staphylococcus aureus is a common bug that can cause serious infections. An antibiotic-resistant strain, called MRSA (methicillin-resistant Staphylococcus aureus), has increased dramatically in recent years. It typically spreads in hospitals. But it's also found in healthy people in the community. It spreads from skin-to-skin contact with someone who is infected, or by touching surfaces contaminated with the germ.
Little is known about places in the environment where MRSA can hide. A study presented today, however, is the first to show that public beaches may be reservoirs for the bug. Staph was isolated in marine water and in intertidal beach sand in nine of 10 public beaches in Washington state, and half of the strains were MRSA, according to the study from researchers at the University of Washington. When examined, those strains appeared to be the type that spreads in hospitals rather than community-acquired MRSA.
How beaches are becoming contaminated with hospital-acquired MRSA is unknown, said the lead author of the study, Dr. Marilyn C. Roberts. The study was presented this morning at the Interscience Conference on Antimicrobial Agents and Chemotherapy in San Francisco.
"Where all these organisms are coming from and how they are getting seeded, we don't know," Roberts said. The samples were "grab-and-go" samples, meaning that researchers didn't spend a lot of time thinking about where to collect the samples. And, Roberts said, "the fact that we found these organisms suggests [beach contamination] is much higher than we normally thought."
Another study on beach sand, published in June in the Journal of Epidemiology, found that people who dug in the sand or covered themselves with sand were more likely to have diarrheal illnesses in the following week or two compared with beachgoers who just walked on the beach or lay on the sand. The most likely scenario for MRSA infection, Roberts said, is getting sand in a cut or abrasion. But the risk of getting MRSA at the beach cannot be estimated at this time.
"We don't know what the risk is because nobody's done a good study," she said.
Roberts also tested two beaches in Southern California and did not find MRSA. But that should not reassure beachgoers in California -- or anywhere. Testing of the samples from California beaches was delayed, which may have affected the quality of the test, Roberts said.
The best advice for beachgoers is to cover open skin wounds and wash off sand thoroughly. People who have weakened immune systems because of other illnesses should take special care with open wounds.
"I'm not telling people not to go to the beach," Roberts said. "But if, all of a sudden, you have a skin rash and it doesn't get better, you need to go and be seen."
-- Shari Roan
Photo credit: Allen J. Schaben / Los Angeles Times