Purpose: An independent study was conducted at ADRIA as part of the NF VALIDATION approval process, in order to extend the scope of the ISO 16140 validation studies to pet food and environmental samples. The ISO 4833, 21528-2, ISO 4832 and ISO 16659 methods were used as reference methods.
Methods: Each ISO 16140 method comparison study of these four Petrifilm plates gathered a linearity study done on 2 (matrix/strain) pairs, a relative accuracy study with 20 samples minimum tested in duplicate.
Results: The Petrifilm Aerobic Count Plate, Enterobacteriaceae Count Plate, Coliform Count Plate and E. coli Count Plate show all satisfying linearity performances, with linear correlation coefficients superior to 0.98. The intercepts close to 0 and the slopes close to 1 were validated for the tested categories in the accuracy study. Biases between the Petrifm plates and the related ISO methods are characterized by low values. The repeatability of the four Petrifilm plates are similar to the compared ISO standards.
Significance: The Petrifilm Total Viable Count Plate, Enterobacteriaceae Count Plate, Coliforms Count Plate and E. coli Count Plate are reliable alternative methods for Total Viable count, Enterobacteriaceae count, Coliform count and E. coli count in pet foods and environmental samples. These four Petrifilm plates offer important economic savings by reducing handling time.