COMPARISON OF POLYMERASE CHAIN-REACTION AND CONVENTIONAL CULTURE FOR THE DETECTION OF LEGIONELLAS IN-HOSPITAL WATER SAMPLES

A detection system for Legionella spp. based on the polymerase chain r eaction (PCR) was used to assess the diagnostic value of PCR for the s urveillance of contamination of man-made water systems by legionellas. A previously-published primer system was chosen to amplify a fragment of the SS-ribosomal gene of Legionella spp. A total of 78 water sampl es from various sources were examined by PCR and culture on MWY Legian ella selective agar. Fifty-seven of 78 water samples were positive by both test systems (73%), nine were positive by PCR only (11.5%), anoth er nine were positive by culture but negative by PCR (11.5%), and thre e were negative by both techniques (3.8%). The PCR was inhibited when large amounts of rust were present in the samples. Culture failed to d etect legionellas in samples that contained large numbers of other bac teria capable of overgrowing the legionellas. These results show that PCR is a rapid and sensitive technique for the detection of legionella contamination in water samples and that PCR and culture complement ea ch other in monitoring of environmental water samples.