A comparison of Legionella pneumophila occurrence in hot water tanks and instantaneous devices in domestic, nosocomial, and community environments

The aim of this study was to compare the occurrence of L. pneumophila in ho t water samples from hot water tanks and instantaneous devices. Tanks and d evices were all operated by heat exchangers employed in the town's district heating system. Thirty-six out of 171 (21%) hot water samples tested posit ive for L. pneumophila isolation, with 14.6% belonging to serogroup 1 and 6 .4% to serogroups 2-14. The proportion of L. pneumophila detected in hot wa ter reservoirs (30%) was higher than that observed in hot water instantaneo us devices (6.2%). Differences in L. pneumophila isolation reflected differ ent temperatures registered at the faucet: less than or equal to 50 degrees C for hot water from reservoir devices, and >60 degreesC for hot water from instantaneous devices. These data emphasize the need to control temperatur e in hot water distribution devices, thus inhibiting the formation of biofi lm and L. pneumophila colonization.