Legionella spp. was isolated from sixtyone percent of the water samples from 46 cooling towers. The isolates were identified as L. pneumophila (serogroup 1, 6 and untyped), L. micdadei, L. dumoffii, and L. bozemanii. A follow-up survey of Legionella in the water of some colling towers was carried out during the summer in 1988. Examination of Legionella in the water was made once a week and the bacterium was found to survive easily in the water when the cooling tower was working every day of the year. The effects of cooling tower biocides on L. pneumophila OCI 8701 were examined. Among the biocides, some agents expressing antibacterial action caused reduction in the number of bacteria in solution. The bacterial population in physiological saline with or without the addition of biocides decreased at higher temperature.
