Survival and Virulence of Enterohemorrhagic Escherichia coli (EHEC) as Affected by pH and Water Activity (9703022)

Enterohemorrhagic Escherichia coli (EHEC) have caused a series of foodborne outbreaks of bloody diarrhea as well as serious complications, including hemolytic uremic syndrome (HUS). While research efforts have been focused on E. coli 0157:H7, it is becoming more evident that other serotypes of EHEC can also be associated with human diseases. An increasing number of non-0157 EHEC have been isolated from humans suffering from HUS and diarrhea. A variety of foods have been implicated in E. coli 0157:H7 outbreaks, particularly foods of bovine origin. Certain foods such as apple cider and dry-cured salami that were considered safe and ready to eat, and are generally not heated before consumption have been identified as transmitting vehicle in E. coli 0157:H7 outbreaks. Unlike 0157:H7, most of non-0157 EHEC serotypes have been isolated from sporadic cases, hence, the significance of food as vehicle for transmitting non-0157 EHEC is not clear. It has been shown that bacterial regulatory responses to environmental conditions are tied to virulence gene expression and that stressful signals in a hostile environment (e.g. acidic and/or dry conditions) can be utilized to induce/enhance virulence gene expression by pathogenic microorganisms. Foodborne pathogens having been exposed to such conditions may become more virulent.