Plasma‐activated carbon nanotube‐based high sensitivity immunosensors for monitoring Legionella pneumophila by direct detection of maltose binding protein peptidoglycan‐associated lipoprotein (MBP‐PAL)

Detection of Legionella by quantitative-Polymerase Chain Reaction (qPCR) for monitoring and risk assessment

Research article Louise H Krojgaard, Karen A Krogfelt, Hans-Jorgen Albrechtsen and Soren A Uldum

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BMC Microbiology 2011, 11:254 doi:10.1186/1471-2180-11-254

Published: 21 November 2011

Background Culture and quantitative polymerase chain reaction (qPCR) assays for the detection of Legionella were compared on samples from a residential area before and after two interventions. A total of 84 samples were collected from shower hoses and taps as first flush samples and at constant temperature. Samples were grouped according to the origin of the sample, a) circulation water b) water from empty apartments c) water from shower hoses. The aims were to investigate the usefulness of qPCR compared to culture for monitoring remedial actions for elimination of Legionella bacteria and as a tool for risk assessment.

In water collected from the apartments Legionella spp were detected by qPCR in the concentration range from LOQ to 9.6*105GU/L while L. pneumophila were detected in a range from LOQ to 6.8 *105 GU/L. By culturing, the legionellae were detected in the range from below detection limit (> 10 CFU/L) to 1.6 * 106 CFU/L. In circulating water and in first flush water from shower hoses, culture and qPCR showed the same tendencies. The overall correlation between the bacteria number detected by culture and the two developed qPCR assays (L. spp and L. pneumophila) was relatively poor (r2 =0.31 for culture and Legionella spp. assay, r2 = 0.20 for culture and L. pneumophila assay).

Detection by qPCR was suitable for monitoring changes in the concentration of Legionella but the precise determination of bacteria is difficult. Risk assessment by qPCR only on samples without any background information regarding treatment, timing, etc is dubious. However, the rapid detection by qPCR of high concentrations of Legionella - especially Legionella pneumophila - is valuable as an indicator of risk, although it may be false positive compared to culture results. On the other hand, the detection of a low number of bacteria by qPCR is a strong indication for the absence of risk.

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Detection of Legionella by quantitative-Polymerase Chain Reaction (qPCR) for monitoring and risk assessment

Conclusion:Detection by qPCR was suitable for monitoring changes in the concentration of Legionella but the precise determination of bacteria is difficult. Risk assessment by qPCR only on samples without any background information regarding treatment, timing, etc is dubious. However, the rapid detection by qPCR of high concentrations of Legionella - especially Legionella pneumophila - is valuable as an indicator of risk, although it may be false positive compared to culture results. On the other hand, the detection of a low number of bacteria by qPCR is a strong indication for the absence of risk. (Source: BMC Microbiology - Latest articles)

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Usefulness of real‐time PCR as a complementary tool to the monitoring of Legionella spp. and Legionella pneumophila by culture in industrial cooling systems

Conclusions: These results suggest that, if some methodological steps designed to reduce inhibitory problems and thus decrease the quantification limits, could be developed to quantify Legionella in complex waters, the real-time PCR could be a valuable complementary tool to monitor the evolution of L. pneumophila concentrations.Significance and Impact of the Study: This study shows the possibility of using real-time PCR to monitor L. pneumophila proliferations in cooling systems and the importance to adapt nucleic acid extraction and purification protocols to raw waters. (Source: Journal of Applied Microbiology)

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