Applied and Environmental Microbiology vol:78 issue:9 pages:3234-3241
High hydrostatic pressure (HHP) processing is becoming a valuable non-thermal food pasteurization technique, although there is reasonable concern that bacterial HHP resistance could compromise the safety and stability of HHP-processed foods. While the degree of natural HHP resistance has already been shown to vary greatly between and within bacterial species, a still unresolved question remains as to what extent different foodborne pathogens can actually develop HHP resistance. In this study, we therefore examined and compared the intrinsic potential for HHP resistance development among strains of Escherichia coli, Shigella flexneri, Salmonella Typhimurium, Salmonella Enteritidis, Yersinia enterocolitica, Aeromonas hydrophila, Pseudomonas aeruginosa and Listeria innocua using a selective enrichment approach. Interestingly, of all strains examined, the acquisition of extreme HHP resistance could only be detected in some of the E. coli strains, indicating that a specific genetic predisposition might be required for resistance development. Furthermore, once acquired, HHP resistance proved to be a very stable trait that was maintained for > 80 generations in the absence of HHP exposure. Finally, at the mechanistic level, HHP resistance was not necessarily linked to derepression of the heat-shock genes, and was not related to the phenomenon of persistence.