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March 1, 2006 By Michael Hopkin This article courtesy of Nature News.

Killer bug could breed inside microscopic water-borne organisms.

The deadly MRSA bug could be lurking in a hitherto unsuspected corner of hospital wards, by hiding away inside amoebae: single-celled organisms that flourish in settings such as hand-wash basins and vases of water.

British researchers have found that the deadly multidrug-resistant Staphylococcus aureus (MRSA) can live and reproduce inside amoebae, as well as being spread from person to person by bodily contact. The discovery, they argue, could mean that hospital personnel may find themselves fighting the killer bug on a new front.

"Amoebae are absolutely everywhere: on every sink in the hospital, and on any source of water," says Mike Brown of the University of Bath, who led the research. "If anyone touches the water, or doesn't wash their hands too well, they could find themselves tapping a new reservoir [of the bacterium]."

Doctors and nurses are currently advised to ensure that they wash their hands thoroughly, in an attempt to curb the spread of the MRSA bacterium, which severely affects around 7,000 hospital patients in Britain each year.

But Brown and his colleagues believe that this may not be enough. They advocate removing sources of water from patients' vicinity, including vases of flowers and open drinking vessels. Although the infection is generally spread from person to person, such reservoirs for amoebae could cause people to pick up the bug after they have disinfected themselves.

Body-building bacteria

Brown and his colleagues make their recommendation after testing the growth of MRSA bacteria inside the amoeba Acanthamoeba polyphaga in the lab. As they report in the journal Environmental Microbiology1, the bacteria were able to infect and grow inside the amoebae, and numbers of free-living MRSA bacterial cells were around 1,000 times greater when cultured alongside A. polyphaga.

"This was certainly not known before," Brown says. And he fears that growing inside amoebae could even cause the MRSA strain to grow in potency. He points to the example of Legionnaire's disease, caused by the bacterium Legionella pneumophila, which becomes more virulent and more resistant to antibiotics after growing inside amoebae. "It's like a gymnasium for bacteria," he says.

Amoeboe are absolutely everywhere - on every sink in the hospital, and on any source of water.
Mike Brown,
University of Bath
It may nevertheless be premature to call for a change in hospital tactics, says MRSA expert Brian Austin of Heriot-Watt University in Edinburgh, UK. He recommends testing basins and other water sources in hospitals to see whether the processes spotted by Brown's team in the lab are actually occurring on the ward.

"I still think the greatest risk to hospitals is from human contact," he says. Austin stresses that the best advice is still to ensure that staff wash their hands properly, and ideally use the antimicrobial hand gel now found on many British hospital wards.

Call in the experts

Brown, on the other hand, points out that there is still not enough awareness among hospital staff of how MRSA spreads. "I don't want to be too controversial, but people don't appreciate the ecology of a hospital; medics have very little microbiological training," he says.

He argues that the best people to consult are pharmacists, who have "ten times more time and experience than doctors" in working with bacteria-free conditions, such as in ensuring that drug preparations are not contaminated.

"Doctors are concerned with treating infections," Brown says. "But industrial pharmacists are more acutely aware of cross-contamination, and have the skills to deal with cross-infections."

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  1. Huws S.A., Smith A.W., Enright M.C., Wood P.J., Brown M.R.W., et al. Env. Microbiol., . - doi:10.1111/j.1462-2920.2006.00991.x (2006).


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