Application of ISO 16140-3:2021 standard to verify compact dry BC method in a single food microbiology laboratory

Abstract

According to clause 7.2.1.5, it is essential that a laboratory that follows the ISO/IEC 17025:2017 standard verifies standard methods or validated alternative methods before it starts using them. In 2021, the International Standard Organization published the ISO 16140-3:2021 standard. This standard provides guidelines for verification of reference methods and validated alternative methods in a single food microbiology laboratory. By using the guidelines provided in the standard, we performed the method verification of Compact Dry BC, a ready-to-use media for quantification of Bacillus cereus in foods or raw materials. This Compact Dry BC method was validated by MicroVal according to the ISO 16140-2:2016 standard and revealed to be at least equivalent to the reference method “ISO 7932: 2004—Microbiology of food and animal feeding stuffs—Horizontal method for the enumeration of presumptive Bacillus cereus—Colony count technique at 30 °C”. For implementation verification, the laboratory selected dried infant formula samples, while for food item verification, the laboratory chose dried infant formula, canned fish, breakfast cereal, sliced meat and pie samples. Intralaboratory reproducibility standard deviation (S_IR) obtained by the laboratory was 0.055 log₁₀ CFU, while the acceptable S_IR is ≤ 0.341 log₁₀ CFU. Estimated bias (eBias) for dried infant formula, canned fish, breakfast cereal, sliced meat and pie samples were also found to be ≤ 0.5 log₁₀ CFU for low, medium, and high inoculum levels. Therefore, as per the criteria set by the ISO 16140-3:2021 standard, the Compact Dry BC method is suitable to use in our laboratory for enumeration of presumptive B. cereus in a broad range of food.