Cronobacter spp. are emerging opportunistic pathogens commonly associated with the feeding of powdered infant formula (PIF). This study aimed to investigate the ability of C.sakazakii (ATCC 29544) to survive heat injury in laboratory growth medium and powdered infant formula (PIF) in comparison to Escherichia coli (ATCC 25922) and other selected Cronobacter strains. As part of this work the thin agar layer (TAL) method for the recovery of heat-injured foodborne pathogens was evaluated for use with C.sakazakii (ATCC 29544) and E.coli (ATCC 25922). We report that heat treatment at 55°C for 10 minutes had no significant effect (P > 0.05) on C.sakazakii (ATCC 29544) viability in peptone or PIF. Significant differences in survival of Cronobacter strains after this heat treatment were identified indicating that heat tolerance in this genus may be strain dependent. PIF did not enhance survival of this organism in comparison to other media. Results indicate that a decrease in temperature of 5°C from the recommended 70°C for the reconstitution of PIF was sufficient to produce a significant increase in survival of C.sakazakii (ATCC 29544). Reconstituted PIF stored at room temperature was shown to support the survival and proliferation of this pathogen indicating that temperature abuse during PIF preparation and storage may significantly increase the risk of disease caused by these opportunistic pathogens.
Cronobacter, powdered infant formula, heat-injury, thin agar layer