Over the past 15 years, multiple foodborne outbreaks have occurred in Canada due to the presence of Salmonella enterica in frozen breaded chicken products. These chicken products were raw and required cooking in conventional household ovens to inactivate any pathogens that they may have been harboring. During the course of food safety investigations associated with these outbreaks, many consumers reported using alternative household appliances such as air fryers to cook these products. The effectiveness of these appliances for the inactivation of pathogens in food is not known. Here, we compare the ability of a toaster oven, air fryer, deep fryer, and conventional oven to inactivate a cocktail of Salmonella Enteritidis in frozen breaded chicken strips. Deep frying was the most effective cooking method, demonstrating a median 7-log reduction; the conventional oven was next with a median 6-log reduction. Both the air fryer and toaster oven performed poorly, with respective median 4- and 3-log reductions. Overall, the results of this study suggest the revision of cooking instructions is required for the safe household use of toaster ovens and air fryers.
HIGHLIGHTS
Whole genome sequencing (WGS) is rapidly replacing other molecular techniques for identifying and subtyping bacterial isolates. The resolution or discrimination offered by WGS is significantly higher than that offered by other molecular techniques, and WGS readily allows infrequent differences that occur between 2 closely related strains to be found. In this investigation, WGS was used to identify the changes that occurred in the genomes of 13 strains of bacterial foodborne pathogens after 100 serial subcultures. Pure cultures of Shiga-toxin-producing Escherichia coli, Salmonella enterica, Listeria monocytogenes, and Vibrio parahaemolyticus were subcultured daily for 100 successive days. The 1st and 100th subcultures were whole-genome sequenced using short-read sequencing. Single nucleotide polymorphisms (SNPs) were identified between the 1st and final culture using 2 different approaches, and multilocus sequence typing of the whole genome was also performed to detect any changes at the allelic level. The number of observed genomic changes varied by strain, species, and the SNP caller used. This study provides insight into the genomic variation that can be detected using next-generation sequencing and analysis methods after repeated subculturing of 4 important bacterial pathogens.
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