Purpose: This study aimed to verify performance of an alternative selective enrichment broth for 300g probiotic PIF samples, followed by the Thermo Scientific™ SureTect™ Cronobacter species PCR Assay against the proposed ISO method with 10g probiotic PIF samples.
Methods: Eighteen samples from five different probiotic PIF brands were spiked with 0-10 CFU per sample of desiccated Cronobacter. Samples were diluted 1/10 in either BPW or the alternative selective enrichment broth and incubated at 37±2°C for 16-19 hours. Post incubation, samples enriched with the alternative broth were tested using the SureTect Cronobacter spp. Assay. Culture confirmations were performed for all samples as detailed in the ISO method.
Results: The SureTect Assay method correctly identified an additional 11% of samples as positive compared to the ISO method after 16 hours enrichment, rising to 33% after 19 hours. The pH dropped during enrichment between 16 and 19 hours, likely caused by growth of LAB, which resulted in die-off of Cronobacterspp. The pH of ISO samples post enrichment was on average 2 pH units lower than the corresponding enrichment broth used with the SureTect Assay method.
Significance: The proposed new SureTect Assay method for detection of Cronobacter spp. with 300g PIF samples outperforms the ISO method when analysing 10g samples. The SureTect Assay method is faster and detects the presence of Cronobacterspecies in a higher number of samples compared with the ISO method.