Twelve samples of water taken from the cooling tower of UOEH were examined for the presence of microorganisms belonging to the genus Legionella by using a new selective medium, Wadowsky-Yee-Okuda (WYO) medium. Three samples contained this organism and they were identified as Legionella pneumophila from their biochemical properties. Among the three contaminated samples, two yielded L. pneumophila serogroup 1 and 3, and the other contained only L. pneumophila serogroup 1. One of the samples of the contaminated cooling tower water was treated with sodium hypochlorite as a disinfectant, indicating that this agent is probably not effective in eliminating L. pneumophila from cooling tower water at that concentration. An effective method of disinfection for Legionella spp. in the cooling tower must be developed to prevent infection in the hospital.
