Thermal resistance and characterization of Escherichia coli O157:H7.

摘要

Escherichia coli 0157:H7 is a highly virulent bacterium whose transmission to humans has been recently linked to the consumption of muscle foods. There have been sixteen documented foodborne disease outbreaks caused by E. coli 0157:H7, of which most have been attributed to consumption of under cooked hamburgers. Other outbreaks have been attributed to consumption of contaminated poultry products. In this study, the heat resistance of three isolates (301C, 204P, and 505B) of E. coli 0157:H7 was quantified by calculation of D- and z-values. Isolate 505b was the least heat resistant; whereas, 204P was the most heat resistant.;Different types of media were evaluated for recovery of thermally-injured Escherichia coli 0157:H7. Phenol red sorbitol agar (PRSA) was the most effective medium for recovering and differentiating E. coli 0157:H7, while highly selective media (e.g MacConkey sorbitol agar) was inadequate for recovering sub-lethally injured cells. Product composition and effect of heat on the lethality of E. coli 0157:H7 in meat and poultry products were studied. Product composition significantly (P ;Characterization and biotyping of the 3 isolates of Escherichia coli 0157:H7 were conducted using biochemical profiling, fatty acid analysis and DNA analysis via polymerase chain reaction (PCR). The three isolates appear to be similar in their growth characteristics based on their response in the 96 biochemical tests. Differences, however, were noted in the fatty acid and DNA profiles. The most heat resistant isolate produced a fatty acid profile distinct from the other more sensitive isolates. The most heat sensitive isolate, also lacked the DNA fragment isolate associated with toxin production. Thus, the 3 strains tested here were closely related, but phenotypically and genotypically different. These differences may, in part, account for differences in heat resistance.