Multidrug-Resistant Staph Found on Puget Sound Beaches

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.

Dr. Marilyn Roberts (Photo courtesy ICAAC)

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."

One of the many beaches that ring the Puget Sound (Photo by Flying Kayaks)

She said sewage outflows were the most likely source of the MRSA found on the sampled beaches,

"There are sewage outflows in the urban settings, but there was not an outflow in the rural setting," she said. "In one of the areas there was a dog park above on a hill, and certainly if there was shedding going on and then rain can wash things down. There is some literature to suggest you get more isolates after rain, but we collected samples in the summer when there was little rain."

Dr. Roberts said more research is needed to pinpoint the source or sources of the MRSA.

"Where all these organisms are coming from is not clear," said Roberts. "We don't know if the organisms were transient or if we could go back again and again and find the identical strain."

She explained that the sampling was a one time event that she called "a grab and go," saying the researchers probably did not find all the MRSA that was really there.

"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.

"If you were just laying on the sand to get suntanned and not digging in it - that is not a risk factor," she said. "If you were actively digging it or buried in it brought a lot of sand all over you that is a risk factor."

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.

"The message is," she said, "that if you've got a scrape or a cut, if you want to to play in the sand, great, but make sure you clean it very well and watch it and if you get something that looks like an infection and it doesn't go away in a couple of days, you go and get seen. That's the best protection. I'm not telling people not to go to the beach."

Copyright Environment News Service, ENS, 2009. All rights reserved.