Validation of the Assurance® GDS for Cronobacter Tq II in Infant Formulas, Infant Cereals, Ingredients, and Environmental Samples Collaborative Study: First Action 2021.08

BACKGROUND: The Assurance® GDS for Cronobacter Tq II assay is a nucleic acid amplification system for the qualitative detection of Cronobacter. The method uses an upfront concentration of the target organism from the enrichment by immunomagnetic separation (IMS) using the PickPen® device.

OBJECTIVE: The Assurance GDS for Cronobacter Tq II method was evaluated for Official Methods of AnalysisSM certification.

METHOD: The matrix was compared to the ISO 22964:2017: Microbiology of the Food Chain-Horizontal Method for the Detection of Cronobacter spp. standard and using an alternative confirmation procedure. The alternative method was evaluated using 10 g test portions in an unpaired study design for powdered infant formula (milk based with iron and DHA) containing probiotics. Eleven technicians from eight laboratories located within the United States and Europe participated in the collaborative study. Statistical analysis was conducted according to the probability of detection (POD) statistical model as presented in the AOAC validation guidelines. The difference in laboratory POD (dLPODC) values with 95% confidence intervals across collaborators was calculated for each level between the candidate and reference method results and between the candidate presumptive and confirmed results.

RESULTS: Results obtained for the low inoculum level test portions produced a dLPOD value with a 95% confidence interval of 0.03 (-0.18, 0.15). The dLPOD results indicate equivalence between the candidate method and reference method for the matrix evaluated. The method also demonstrated acceptable inter-laboratory reproducibility as determined in the collaborative evaluation. There were no false negative results; the false positive rate was determined and produced a value of <2%.

CONCLUSIONS: Based on the data generated, the method demonstrated Assurance GDS for Cronobacter Tq II assay produced acceptable interlaboratory reproducibility data and statistical analysis.

HIGHLIGHTS: The Assurance GDS for Cronobacter Tq II method is suitable for the rapid qualitative detection of Cronobacter in infant formulas, infant cereals, ingredients, and environmental samples.