Interlaboratory proficiency tests to assess the analytical competency of French official control laboratories for the analysis of Listeria monocytogenes, Salmonella spp. and coagulase-positive staphylococci in food.

A common interlaboratory proficiency testing scheme in food microbiology was organised yearly in France from 2019 to 2021 by the three National Reference Laboratories for Listeria monocytogenes, Salmonella spp. and coagulase-positive staphylococci (CPS). This proficiency testing scheme aimed to assess the performance of French official control laboratories for the detection and enumeration of these three major foodborne pathogenic bacteria covered by European regulations on microbiological criteria for foodstuffs. An average of 65 laboratories participated in the proficiency test (PT) each year, using either reference or validated alternative methods. For each PT, ten samples for detection and four samples for enumeration per pathogen were sent to each participant. Over the three years, the PT results demonstrated the ability of the laboratory network to detect L. monocytogenes and Salmonella spp., as well as to enumerate L. monocytogenes and CPS in food matrices. These PTs showcased the robustness of the official laboratory network and provided an opportunity to give scientific and technical advices in case of discrepancy results, representing an efficient tool for quality improvement of the analyses performed by the laboratory network.