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Appl. Environ. Microbiol., 07 1997, 2489-2494, Vol 63, No. 7
H Miyamoto, H Yamamoto, K Arima, J Fujii, K Maruta, K Izu, T Shiomori and S Yoshida
The presence of PCR inhibitors in water samples is well known and
contributes to the fact that a practical PCR assay has not been developed
for legionella surveillance. In this study, we devised a new seminested PCR
assay for detection of Legionella spp. in water samples as a means of
overriding the PCR inhibitors without loss of sensitivity. The seminested
PCR assay utilized primers to amplify the 16S rRNA gene (LEG primers) of 39
Legionella spp. The assay was specific to legionellae, and the sensitivity
was 1 fg of extracted Legionella DNA in laboratory examination. To evaluate
the feasibility and sensitivity of the PCR assay in identifying the
presence of legionellae, it was used to survey Legionella contamination in
the water of 49 cooling towers of 32 hospitals. A commercially available
EnviroAmp Legionella kit and a culture method were also used in the survey
for comparison with the seminested PCR assay. The detection rates of
legionellae in the samples were 91.8% (45 of 49) by the PCR assay and 79.5%
(39 of 49) by the culture method. The EnviroAmp kit revealed that 30.6% of
the water samples (15 of 49) contained inhibitors of the PCR amplification.
However, the seminested PCR assay could produce the Legionella-specific DNA
bands in 14 of the 15 samples. Although 8 of the 14 samples were positive
in the first-step PCR, 6 of the 14 samples became positive in the
second-step PCR. These results suggest that the effect of PCR inhibitors in
samples, if any, can be reduced because of the dilution of the sample in
the second-step PCR and that sensitivity of detection can be increased by
the second- step PCR. Thus, the seminested PCR assay with LEG primers to
amplify the 16S rRNA gene of 39 Legionella spp. was a practical and
sensitive method to detect Legionella spp. in water samples.
Copyright © 1997, American Society for Microbiology
Development of a new seminested PCR method for detection of Legionella species and its application to surveillance of legionellae in hospital cooling tower water
Department of Microbiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan. miyamoto@med.uoeh-u.ac.jp
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