The cooling towers on top of many large, commercial buildings may hold high numbers of infected amoebas, a threat to human health as illustrated by the 1976 outbreak of Legionnaires' disease.
Results of a new study published online by Environmental Science & Technology suggest these amoebas infected with bacteria are more prevalent in cooling towers than in natural environments. Sharon Berk of Tennessee Technological University and colleagues sampled 40 cooling towers in hospitals, universities and industries and 40 natural environments—lakes, rivers, creeks and ponds—finding infected amoebas in 22 of the cooling towers and only three of the natural samples.
"The bacteria responsible for Legionnaire's disease use amoebas as a host, as do many related bacteria," said Berk, a TTU biology professor.
The bacteria can then hijack the amoeba's cellular machinery and then multiply profusely. According to Berk, eventually the amoeba swells and bursts like a balloon, releasing the bacteria by the hundreds.
People can contract pneumonia after inhaling Legionella in aerosol drifts from cooling towers, according to a related ES&T article. It is possible that other amoeba-associated microorganisms, such as those found in cooling towers in the study, may be unrecognized causes of other respiratory disease.
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