DETECTION OF LEGIONELLA SPECIES IN RECLAIMED WATER AND AIR WITH THE ENVIROAMP LEGIONELLA PCR KIT AND DIRECT FLUORESCENT-ANTIBODY STAINING

Reclaimed water is an important resource for areas with inadequate wat er supplies. However, there have been few studies on the variety of mi croorganisms found in this type of water, since typically reclaimed wa ter is examined only for the presence of coliform bacteria. Many micro organisms, including the legionellae, are known to be more resistant t o chlorine than are coliform bacteria. Previously, we detected >10(3) Legionella cells per mi in primary and secondary sewage effluents and observed no significant reduction in population numbers throughout the treatment process. In this study, we detected Legionella spp. in chlo rinated effluent by using an EnviroAmp Legionella PCR kit and direct f luorescent antibody (DFA) staining. However, we were not able to isola te Legionella spp. from either natural or seeded reclaimed water sampl es. This suggests that the Legionella spp. detected by the PCR and DFA methods may be injured or viable but nonculturable after exposure to the high residual chlorine levels typically found in this type of wate r source. The numbers of coliform bacteria were low (<2 cells per 100 mt) in most reclaimed water samples and were not correlated with the p resence or absence of Legionella spp. We also collected air samples fr om above a secondary aeration basin and analyzed them by using the PCR , DFA, and plate culture methods. Legionella spp. were detected in the air obtained from above the secondary basin with all three methods. W e concluded that the PCR was superior to the culture and DFA methods f or detecting Legionella spp. in environmental water samples.