Transcriptomic response of Escherichia coli O157 isolates on meat: Comparison between a typical Australian isolate...

The majority of foodborne illnesses associated with E. coli O157 are attributed to the consumption of foods of bovine origin. In this study, RNA-Seq experiments were undertaken with E. coli O157 to identify genes that may be associated with growth and survival on meat and the beef carcass at low temperature. In addition, the response of an E. coli O157 isolate representative of the general genetic 'type' found in Australia (E. coli O157:H^- strain EC2422) was compared to that of a pathogenic clinical isolate (E. coli O157:H7 strain Sakai) not typically found in Australia. Both strains up-regulated genes involved in the acid stress response, cold shock response, quorum sensing, biofilm formation and Shiga toxin production. Differences were also observed, with E. coli O157:H7 Sakai up-regulating genes playing a critical role in the barrier function of the outer membrane, lipopolysaccharide biosynthesis, extracellular polysaccharide synthesis and curli production. In contrast, E. coli O157:H^- EC2422 down-regulated genes involved in peptidoglycan biosynthesis and of the primary envelope stress response Cpx system. The unique gene expression profiles of the strains, indicate that these genotypes may differ in their ability to persist in the meat production environment and therefore also in their ability to cause disease.