Samples of sand and water from five beaches around the Puget Sound have tested positive for a multidrug resistant form of the bacteria Staphylococcus aureus. This potentially fatal strain of staph is resistant to the broad-spectrum antibiotics commonly used to treat it.
Dr. Marilyn Roberts, a professor of environmental and health science at the University of Washington in Seattle, Firday reported the first isolation of Methicillin resistant staphylococcus aureus, MRSA, from marine and beach sand samples taken from public beaches in Washington state.
Speaking at the Interscience Conference on Antimicrobial Agents and Chemotherapy in San Francisco, Dr. Roberts did not identify the individual beaches where the dangerous bacteria was found.
She said the MRSA bacteria was found in samples at four urban beaches and one rural beach about 10 miles apart around the Puget Sound.
"We found the same strain in three different beaches," said Roberts. "It's possible there was a common source. It could have been a hospital, could have been a person or people, but we don't really know where it came from or how three beaches got same strain," she told colleagues at the conference.
Most MRSA infections occur in hospitals or other health care settings, such as nursing homes and dialysis centers. More recently, another type of MRSA has occurred among otherwise healthy people in the wider community. This community-associated MRSA is responsible for serious skin and soft tissue infections and for a serious form of pneumonia.
Dr. Roberts said, "In most cases people who acquire it do not have an association with hospitals, do not work there, do not visit there, so the assumption is you've got MRSA out in the environment."
She said sewage outflows were the most likely source of the MRSA found on the sampled beaches...
"The fact that we found these organisms suggests that the level was much higher that one would have thought," she said.
"We don't really know the risk for people going to the beach," said Dr. Roberts. She cited a survey of 27,000 people published this year in the "Journal of Epidemiology" that found that people who dug in the sand or were completely covered by sand were much more likely to come down with a diarrheal disaease than those who did not engage in these activities and suggested that being covered with sand might also be a risk factor for MRSA...
Because the Puget Sound water is cold, between 50 and 58 degrees, and MRSA is salt-resistant, the organism can survive, Roberts said, and she added that it can also survive hospital cleaning and the laundering of hospital linens.
"All disinfectants do not give you a 100 percent kill," she said. "Hot water does a better job than cold water, but virtually nothing that anyone has will give 100 percent rate kill unless you autoclave," she said of the process used to sterilize surgical instruments by heating them under pressure.