Purpose: Growth promotion and isolation of Cronobacter spp. and Cronobacter-related species were tested and confirmed with BPW, CSB and CCI agar, as described by EN ISO 22964:2017.
Methods: For growth promotion >15 Cronobacter spp. strains, >10 Franconibacter spp. and 3 Siccibacter spp. strains, including type strains and wild isolates from food and environmental samples and C. sakazakii reference material, were spiked into the food matrix for evaluating the media within the entire workflow. Performance tests for productivity, selectivity, and specificity were conducted, as given by the EN ISO standard, for the quality assuarance of the culture media.
Results: All Cronobacter spp. and non-Cronobacter strains from pure strains, spiked into reference material, were able to be detected, following the method given by the revised standard: non-selective pre-enrichment in BPW, incubation between 34-38°C for 18 h ± 2h, followed by selective enrichment in CSB, incubation at 41.5 °C ± 1 °C for 24 ± 2h, and plating (incubation at 41,5 °C ± 1 °C for 24 ± 2h) and identification on CCI agar. Productivity, selectivity, and specificity of the media affected the performance, as specified by the standard.
Significance: For the tested Granucult®, using BPW, CSB, and Chromocult® CCI agar, the results of this study indicate the applicability of the methods and criteria, as given in the revised International Standard EN ISO 22964:2017, “Microbiology of the food chain - Horizontal method for the detection of Cronobacter spp.”