Prevention of legionella infections from toilet flushing cisterns

Abstract

INTRODUCTIONImmunocompromised patients are at an increased risk of severe Legionella infections. We present the results of an outbreak investigation initiated following a fatal case of hospital-acquired legionellosis linked to contaminated water from a toilet-flushing cistern. Additionally, we provide experimental data on the growth of Legionella spp. in flushing cisterns and propose a straightforward protocol for prevention. METHODSWe monitored the growth of Legionella spp. in the building's hot and cold-water systems using quantitative bacterial culture on selective agar. Molecular typing of L. pneumophila isolates from the infected patient and the water system was conducted through core-genome multilocus sequence typing (cgMLST). RESULTSLegionella contamination in the hospital building’s cold-water system was significantly higher than in the hot water system and significantly higher in toilet flushing cistern’s water compared to cold water from bathroom sinks and showers. Isolates from the patient and from the flushing cistern of the patient’s bathroom were identical by cgMLST. In an experimental setting, daily toilet flushing for a period of 21 days resulted in a 67 percent reduction in the growth of Legionella spp. in the water of toilet flushing cisterns. Moreover, a one-time disinfection of cisterns with peracetic acid, followed by daily flushing, decreased Legionella growth to less than 1% over a period of at least 7 weeks in these setting. CONCLUSIONSOne-time disinfection of highly contaminated cisterns with peracetic acid and daily toilet flushing as short-term measure can significantly reduce Legionella contamination in flushing cisterns. These measures may aid in preventing Legionella infection among immunocompromised patients.