Open AccessQuantitative Real-Time Legionella PCR for Environmental Water Samples: Data Interpretation
Author(s) -
Philippe Joly,
Pierre-Alain Falconnet,
Janine André,
Nicole Weill,
M. Reyrolle,
François Vandenesch,
Max Maurin,
Jérôme Etienne,
Sophie Jarraud
Publication year - 2006
Publication title -
applied and environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.552
H-Index - 324
eISSN - 1070-6291
pISSN - 0099-2240
DOI - 10.1128/aem.72.4.2801-2808.2006
Subject(s) - legionella , legionella pneumophila , 16s ribosomal rna , biology , microbiology and biotechnology , cooling tower , real time polymerase chain reaction , polymerase chain reaction , veterinary medicine , bacteria , water cooling , gene , genetics , medicine , mechanical engineering , engineering
Quantitative Legionella PCRs targeting the 16S rRNA gene (specific for the genus Legionella) and the mip gene (specific for the species Legionella pneumophila) were applied to a total of 223 hot water system samples (131 in one laboratory and 92 in another laboratory) and 37 cooling tower samples (all in the same laboratory). The PCR results were compared with those of conventional culture. 16S rRNA gene PCR results were nonquantifiable for 2.8% of cooling tower samples and up to 39.1% of hot water system samples, and this was highly predictive of Legionella CFU counts below 250/liter. PCR cutoff values for identifying hot water system samples containing >10(3) CFU/liter legionellae were determined separately in each laboratory. The cutoffs differed widely between the laboratories and had sensitivities from 87.7 to 92.9% and specificities from 77.3 to 96.5%. The best specificity was obtained with mip PCR. PCR cutoffs could not be determined for cooling tower samples, as the results were highly variable and often high for culture-negative samples. Thus, quantitative Legionella PCR appears to be applicable to samples from hot water systems, but the positivity cutoff has to be determined in each laboratory.