Proficiency testing in food microbiology “Aqua”: enumeration of Staphylococcus aureus

In 1999 the Food Microbiology laboratory of the Istituto Zooprofilattico Sperimentale delle Venezie (IZSVe) started an interlaboratory comparison program for food microbiological tests, known as “Aqua, interlaboratory comparisons for quality assurance”. Aqua produces the test samples, applies statistical methods to estimate homogeneity and stability, processes and evaluates the results. The proficiency testing results allow to evaluate the performance of the laboratories, to identify possible differences and non-conformity, to demonstrate the competence and the quality of results, in order to take suitable corrective and/or preventive action after the individuation of the causes. Moreover, elaborating the results of several proficiency testing by using the control chart method, it is possible to evaluate the trend of the laboratory and to verify that the results are in statistical quality control.