An Interlaboratory Method Applicability Study of GB 4789.40-2016 and ISO 22964:2017 for the Detection of Cronobacter spp. in Powdered Infant Formula

It is documented that Cronobacter spp. (formely Enterobacter sakazakii) can survive in powdered infant formula (PIF) for a long period, and special concerns have been raised about the safety of powdered infant formula (PIF) contaminated by Cronobacter spp. with the globalization of the food supply. This study compared the methods for detecting Cronobacter spp. in PIF of the Chinese standard method GB 4789.40-2016 (reference method) and the European standard method EN ISO 22964:2017 (alternative method) according to the principle requirements of method comparison in ISO 16140-2 2016. A total of 576 blind-coded test portions of the product spiked with the test strain at three different contamination levels (0 MPN/ 10 g, 1.299 MPN/10 g and 2.210 PMN/10 g) were analyzed by 12 participating laboratories. The results showed that the sensitivity of GB 4789.40-2016 was 80.00% at the low contamination level and 81.16% at the high level, while those of ISO 22964:2017 were 90.00% and 97.10%, respectively. The relative levels of detection (RLODs) were below the acceptance limit (AL=2.5) regardless of the contamination level, and the probability of detection (POD) model proposed in the AOAC guidelines was analyzed. Results revealed no statistically significant difference between the alternative and reference methods. It was concluded that the GB 4789.40-2016 method for the detection of C. sakazakii in PIF was equivalent to the ISO 22964:2017 method.