Detection of Legionella Spp. in Water from Cooling Towers

Legionella are Gram negative and non-spore bacteria which are found in various natural and manmade aquatic environments. Legionella can cause legionnaire's disease or Pontiac fever. Inhalation of aerosols from contaminated water sources leads to Legionella infections or legionellosis. Contamination of waters from cooling towers with Legionella was recognized as a major source for legionellosis. Therefore, this study was conducted to survey the Legionella contamination of waters from cooling towers. A total of 33 water samples were taken from cooling towers. After measuring temperature and pH, the samples were examined for the presence of Legionella in two methods of culture and polymerase chain reaction (PCR). We also evaluated turbidity, iron, magnesium, zinc, and copper content, and heterotrophic bacteria of the samples. From the 33 cooling towers examined, 15% and 70% of the samples were positive for Legionella by the culture method and nested PCR, respectively. Biochemical tests showed Legionella pneumophila to be the main detected species in contaminated water samples. The results of the study indicated that cooling towers can potentially transmit Legionella infections. Therefore, regular monitoring and application of control measures such as disinfection of waters of cooling towers are needed to minimize human exposure to Legionella, especially in hospital environments with high risk patients.