Amoebae Help Spread MRSA Infections

Researchers have found that amoeba contribute to the survival and transmission of methicillin-resistant Staphylococcus aureus (MRSA) especially in the hospital environment.

At the end of August 2004, after a successful pilot scheme to tackle MRSA, the British National Health Service announced a "Clean Your Hands” campaign. Wards were required to ensure that alcohol-based hand rubs were placed near to all beds so that staff could hand wash more regularly. It was thought that if this reduced incidence of infection by just 1% the plan would pay for itself many times over. In spite of this, as of early 2005, the number of deaths in the United Kingdom attributed to MRSA was estimated by various sources to lie in the area of 800 to 955 per year.

Investigators at the University of Bath (UK) examined the interaction between MRSA bacteria and the common environmental amoeba Acanthamoeba polyphaga. Their findings, published in the February 16, 2006, online edition of Environmental Microbiology, revealed that MRSA proliferated in the presence of amoebae, attributable partly to intracellular replication. Following 24 hours of co-culture, confocal microscopy revealed that about half of the amoeba culture had viable MRSA within phago-lysosomes and 2% of amoebae were heavily infected with viable cocci throughout the cytoplasm.

"Until now this source of MRSA had been totally unrecognized,” said senior author Dr. Michael R. W. Brown, professor of pharmacology at the University of Bath. "This is a non-patient source of replication and given that amoeba and other protozoa are ubiquitous, including in hospitals, they are likely to contribute to the persistence of MRSA in the hospital environment. Infection control policies for hospitals should recognize the role played by amoeba in the survival of MRSA, and evaluate control procedures accordingly.”


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