Proficiency testing schemes for the assessment of Legionella PCR methodologies

Standard operating procedures used for the detection of bacteria in environmental samples are primarily based on bacterial growth on specific culture media and confirmation by biochemical and/or immunological tests. In the case of Legionella, isolation on BCYE-alpha medium is the standard method, although it presents a number of drawbacks, and for this reason, the implementation of molecular methods, mainly those based on PCR, has increased over the last years. Following the ISO/IEC 17025, laboratories need an external evaluation of their work to assure the quality of the results they are producing, and the participation in proficiency testing (PT) schemes is compulsory. For those water-testing laboratories using PCR methods for Legionella, we have developed a PT scheme accredited according to ISO/IEC 17043. The preparation and the statistical analysis of the results are performed following this standard and the ISO 13528. The used samples have a very rapid and easy to use format, consisting of tablets with inactivated freeze-dried Legionella cells or freeze-dried Legionella DNA. In this PT scheme, participants evaluate both Legionella pneumophila and Legionella spp. detection systems and control the whole PCR process from the water sample concentration until the PCR results.