COMPARISON OF CONVENTIONAL CULTURE AND PCR METHODS FOR THE DETECTION OF LEGIONELLA-PNEUMOPHILA IN WATER

A comparative assessment of conventional culture and nucleic acid tech niques in the detection of Legionella pneumophila in seeded tap water samples was performed, using bacterial concentrations ranging from 994 to 0.015 cfu ml(-1). Different filtration and centrifugation protocol s were evaluated. The results permitted the development of a tentative algorithm for the detection of legionellae in tap water. Samples shou ld first be analysed using PCR methods. In the event of quantitative d ata and bacterial strains for epidemiologic typing being required, the same sample, or a greater volume of the sample, if positive with PCR, can be re-tested by filtration through polycarbonate membranes follow ed by plating a homogenate of the filter. If samples are found to be n egative with PCR, they can be re-analysed in greater volumes by filtra tion through polycarbonate membranes followed by direct placing of the filter on culture media, to allow detection of very low numbers of ba cteria. This protocol should be validated in the field before it can b e routinely implemented.