Purpose: An independent study was conducted at Adria, to validate this method in comparison to the ISO 7932 standard, as part of the MicroVal approval process and according to the ISO 16140-2 standard.
Methods: The relative trueness study, the accuracy profiles and the limits of quantification were determined for 5 food categories and environmental samples. The inclusivity and exclusivity testing was run with 50 target strains from the B. cereus group and 33 non target strains. The inter-laboratory study was run with 17 different laboratories.
Results: One hundred sixty-four samples were analyzed in the relative trueness part, 101 provided interpretable results. The data of the alternative and the reference methods were analyzed with the Scatter and Bland-Altman plots, and only few differences higher than 0.5 log CFU/g were observed leading to 3 positive and 8 negative deviations. The 6 accuracy profiles are within the acceptability limits defined in the ISO 16140-2 standard, i.e., 0.5 log CFU/g. Whatever the tested matrix, the quantification limit is 0. All the tested B. cereus group strains were correctly enumerated. Within the non-target strains, only one Lysinibacillus fusiformis strain on the three tested ones was detected by the alternative method giving a very low result, i.e., 2 log less than the control medium. The statistical calculations done with the ring trial data clearly showed that the tolerance interval limits of the alternative method are within the acceptable limits of 0.5 log.
Significance: The performance criteria are fulfilled for all the ISO 16140-2 study parts, demonstrating that the TEMPO® BC method is equivalent to the ISO 7932 standard for B. cereus enumeration in a broad range of foods and environmental samples. Moreover, TEMPO® BC offers important economic savings by reducing time to result and handling time.