Prevalence of Legionella spp. in swimming pool environment

A study was carried out to evaluate the prevalence of bacteria of the Legio nella genus in the water from the pools and showers of 12 swimming pools in the city of Bologna (Italy), Sampling took place four times for every esta blishment, once for each season of the year. Legionella spp. were found in 2 of the 48 pool water samples (L. micdadei and L. bozemanii) and in 27 of the 48 samples taken from the hot water of the showers: 19 were positive fo r L. pneumophila (10-19,250cfu/l) and 18 for other species (20-6000 cfu/l). The contamination was seen to be consistent throughout the year, since the same species of legionellae were isolated at different samplings and in co ncentrations that did not reveal any seasonal trend. The legionellae and th e Gram negative bacteria were not found in shower water with a temperature above 43 degreesC. However, in the samples of shower water with a lower tem perature a statistically significant inverse correlation was seen between l egionellae and Pseudomonas aeruginosa (r = -0.51; p < 0.01) as well as betw een legionellae and Gram negative bacteria (r = -0.70; p<0.01). The potenti al risk of contracting infections from Legionella spp. in the swimming pool environment does not seem to be linked to the pool water, but to that of t he showers. The water temperature of showers should therefore be maintained at a level high enough to prevent the reproduction of these bacteria. (C) 2001 Elsevier Science Ltd. All rights reserved.