"In industrialized nations, people expect their drinking water to be pathogen free, thanks to treatment facilities that filter and disinfect the water. However, after reviewing 26 studies from 18 countries, two scientists conclude that some amoeba species called free-living amoebas (FLA) consistently survive these treatments and quickly multiply in drinking-water distribution and storage systems. Given their potential to spread disease, these microbes are a human health risk that demands further study, the researchers say.

FLA are protozoa that live independently in water or soil, without the need of a human or animal host. Some FLA can cause fatal diseases such as meningoencephalitis, an infection of the brain. The microbes also host other pathogenic microorganisms, such as Legionella and Mycobacterium. These so-called amoeba-resistant microorganisms avoid digestion by the amoeba and replicate successfully within it. The amoeba helps these bacteria grow in numbers and can increase their virulence, says Jacqueline Thomas, a doctoral student at the University of New South Wales, in Sydney, Australia. She thinks that to control the other microbes, researchers need to understand more about the persistence of the amoebas."

Emily Gertz reports for Chemical & Engineering News January 11, 2011. [2]