Results of International Study of qPCR for Monitoring Legionella

Legionella bacteria have been implicated as the cause of legionellosis (Legionnaire's disease). Current national guidelines and legislation for Legionella surveillance of water systems are based on detection by culture. However, this method is not well-suited to early detection of elevated Legionella levels, and hence is not a rapid, early indicator of infection.

At the 'Legionella 2009' congress at the Pasteur Institute, Paris on Thursday October 15th, Dr. John V. Lee will give a presentation entitled 'An International Trial of Quantitative PCR for Monitoring Legionella in Artificial Water Systems', reporting the findings from a study using data from eight laboratories based across six countries and from over 800 samples.

The objective of this study was to define algorithms to monitor Legionella using quantitative polymerase chain reaction (qPCR), and to define the action thresholds for detection of Legionella based on monitoring using qPCR and culture test results in different types of water systems. Action thresholds established based on qPCR (i.e. an increase in qPCR signal) were compared to those established based on culture.

qPCR technology provides a rapid, robust alternative method to culture and is increasingly used to check for Legionella in water systems. For Legionella surveillance, consistent correlation between qPCR and culture is critical for effective use of qPCR technology. However, these are different methods which do not necessarily provide results that can be directly cross-compared. At present, qPCR results are used in addition to culture results but cannot be used as a substitute for culture in monitoring Legionella - hence the need to develop guidelines that include the use of qPCR, based on extensive field experience.

The data being presented by Dr Lee reaffirms the value of qPCR for Legionella screening. It was possible to establish qPCR thresholds based on existing culture alert and action levels and to decide actions comparable to those based on culture. This study confirms that algorithms for monitoring systems by qPCR can be created, and presents guidelines to inform regulators and public health practitioners of the value and practical application qPCR for monitoring Legionella contamination.

For more information on Pall´s GeneDisc® technology for Legionella, please visit Pall GeneSystems website

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