Superbug Found on Beaches

Public beaches may be one source of the surging prevalence of the superbug known as multidrug-resistant Staphylococcus aureus (Staph aureus), researchers in Los Angeles told USA Today.

A study by researchers at the University of Washington has for the first time identified MRSA in marine water and beach sand from seven public beaches on the Puget Sound.

The researchers identified Staph bacteria on nine of 10 public beaches that they tested. Seven of 13 Staph aureus samples, found on five beaches, were multidrug resistant, says lead investigator, Marilyn Roberts.

"Our results suggest that public beaches may be a reservoir for possible transmission of MRSA," she told the Interscience Conference on Antimicrobial Agents and Chemotherapy, the leading international conference on new and resurgent diseases.

USA Today reports that antibiotic-resistant bacteria have been around for almost as long as there have been antibiotics. Until recently, researchers have been able to outwit them by developing new antibiotics. Now, however, the pipeline of new antibiotics has slowed, and germs are coming perilously close to winning the race.

The best available treatment for MRSA, vancomycin, is more expensive than other antibiotics and takes a long time to conquer the infection. "It's like trying to turn an ocean liner around," says Henry Chambers of the University of California, San Francisco.

Until a decade ago, most multidrug-resistant Staph aureus infections were found in hospitals among severely ill patients. That changed about seven years ago with the emergence of a strain hardy enough, and virulent enough to infect healthy people, usually in their skin and soft tissues.

Since about 30 per cent of healthy people carry Staph aureus, most people are able to survive infection. But it is fatal in about 20 per cent of people who develop MRSA bloodstream infections and 40 per cent of those who develop MRSA pneumonia. It has emerged as a killer of people with severe influenza, including the new H1N1 flu.

Curiously, Dr Roberts says, five of the samples found on the beach and in the sand more closely resembled hospital-acquired MRSA than the bacteria found in the community. Three of the samples, from three beaches 10 miles apart, were virtually identical, she says. "One would think they came from the same source," Dr Roberts added.

The most likely scenario, she says, is that the source is environmental, not human, but "where all of these organisms are coming from and how they're getting seeded (on the beaches) is not clear." Tests of ocean water and sand taken from two beaches in Southern California turned up no Staph aureus at all.

Genetic analysis also suggested that the Puget Sound beaches, and maybe others, may represent an 'ecosystem', where bacteria thrive, mingle and swap genes, particularly those confer antibiotic resistance.

Dr Roberts says there may be much more MRSA than her team's 'grab and go' sampling experiments indicated. She said: "The fact that we found these organisms suggests that the amount is much higher than we previously thought."

Lance Peterson, a University of Chicago infectious disease specialist who was not involved in the study, commented to USA Today: "Staph is a salt-loving organism. It's not surprising to see it in the ocean."