Influence of enteric bacteria conditioned media on recovery of Escherichia coli O157:H7 exposed to starvation and sodium hypochlorite

AIMS: To examine the effect that starvation and sodium hypochlorite stress have on virulence of Escherichia coli O157:H7 and the influence of conditioned media on recovery of stressed cells. METHODS AND RESULTS: Escherichia coli O157:H7 was starved for 5 days then exposed to 1 microg ml(-1) sodium hypochlorite, suspended in defined media Dulbecco's Modified Eagle's Medium supplemented with conditioned media, sampled over a 12-h period; and assayed for growth, production of Shiga toxin (Stx), and attachment to HCT-8 cells. During recovery, stressed and control cells grown in conditioned media exhibited greater attachment efficiencies to HCT-8 cells then cells in DMEM alone. Production of Stx by treated cells mimicked Stx production by control cells suggesting that components of conditioned media assist in recovery. Results showed that levels of autoinducer-2 fluctuate during recovery and growth suggesting involvement of a quorum sensing mechanism during the recovery of stressed E. coli O157:H7. CONCLUSIONS: The recovery of stressed E. coli O157:H7 exposed to starvation conditions and HOCl is positively affected by the presence of autoinducer-2 thereby influencing virulence factor production. SIGNIFICANCE AND IMPACT OF THE STUDY: Food-borne pathogens in a stressed state prior to ingestion can rapidly recover in the presence of bacterial by-products; exhibiting virulence characteristics and presenting a microbial food safety hazard.