2013 Annual Report
Research was done to investigate the acid resistance of 100 or more pathogenic Escherichia coli serotypes, including outbreak strains such as Escherichia coli O157:H7, and Escherichia coli O104:H4. The ability of these strains to survive in acid solutions at different pH values was determined using a standardized set of conditions that allowed direct comparison of strains from different sources and having different serotpyes. For selected groups of strains, genetic similarity was also determined. Data from acid resistance comparison experiments showed that isolates from animal and environmental sources (bovine carcass, bovine feces, waterborne) were significantly more acid resistant as a group than human isolates. Some serotypes as a group were also more acid than others, although no direct correlation with acid resistance and human disease was determined. The development of acid tolerance by foodborne pathogenic bacteria may be signifcant at several points along the farm-to-table continuum of food production. It is important to understand how previous environment and processing conditions can affect the acid tolerance status of foodborne Escherichia coli O157:H7 in order to devise strategies for better control of the occurrence, growth, or survival of this organism in foods. An additional publication on non-O157 serotype strains is in preparation.