Abstract
Waterborne diseases are a serious threat because of their ability to infect a high number of individuals in a short time span, such as during outbreaks of Legionellosis. This significantly highlights the need for the rapid detection and quantification of bacteria in environmental water samples. The aim of this study was to investigate the feasibility of quantitative Polymerase Chain Reaction (qPCR) for the detection of Legionellapneumophila (L. pneumophila) in environmental water samples and comparison of standard culture methods for Legionella detection with qPCR. Our study reached a negative predictive value (NPV) for L. pneumophila of 80.7% and for L. pneumophila serogroup 1 (sg1) the calculated NPV was 87.0%. The positive predictive value (PPV) for L. pneumophila was 53.9% and for L. pneumophila sg1 PPV was 21.4%. Results showed a correlation between qPCR and culture with an R2 value of 0.8973 for L. pneumophila, whereas no correlation was observed for the detection of L. pneumophila sg1. In our study, qPCR proved useful for the identification of L. pneumophila negative samples. However, despite the obvious benefits (sample handling, rapid generation of results), qPCR needs to be improved regarding the PPV before it can replace culture in water quality assessment.
Highlights
The genus Legionella spp. comprises more than 42 different strains, the best-known beingLegionella pneumophila (L. pneumophila), due to its ability to cause disease
The quantitative Polymerase Chain Reaction (qPCR) detected L. pneumophila in concentrations ranging from 1.44 × 102 to 2.97 × 105 genomic units (GU)/100 mL, respectively, whereas L. pneumophila sg1 was detected at concentrations ranging from 2.78 × 103 to 1.79 × 107 GU/100 mL. qPCR and culture only led to the same result in 56.6% (47) samples
Discussion qPCR has been proposed by several researchers as a fast and less labor-intensive alternative for screening of environmental samples for contamination with Legionella spp. qPCR can be performed out of the same water sample as the culture, so one suggestion of researchers has been that qPCR and culture-dependent methods could be run simultaneously: qPCR could be used as a method for screening out negative samples in as quick as half a day after receipt of the sample in the laboratory, and qPCR negative samples would not go into the culture for testing
Summary
The genus Legionella spp. comprises more than 42 different strains, the best-known beingLegionella pneumophila (L. pneumophila), due to its ability to cause disease. The genus Legionella spp. comprises more than 42 different strains, the best-known being. Is the causative agent in most cases in Europe (70% of all infections) [1]. Legionella pollution for example results from growth in synthetic piped water distribution systems, as generally only low concentrations of Legionella spp. can be found in natural aquatic environments in Europe [2]. Most outbreaks of L. pneumophila infections can be attributed to the human alteration of the environment since Legionella thrive in moist man-made environments [2,4]. To avoid proliferation of Legionella in hot water systems they must be heated on to a minimum of 55 to 60 ◦ C according to the Austrian Standards B 5019. Water systems that produce aerosols are especially under inspection for
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