Evaluation of 5 ' nuclease based detection assays to detect Escherichia coli O157 : H7 from food products

Two 5' nuclease-based PCR methods (PCR-LS-50B and PCR-7200) were evaluated to determine their sensitivity for detecting Escherichia, coli O157.H7 from pure cultures and in food samples enriched in different media and after di fferent incubation periods. The PCR-7200 method was able to detect E. coli O157:H7 at greater than or equal to 10(2) CFU/mL in pure culture in both mE CB and EEB. In spiked meat samples, the PCR-7200 procedure was capable of d etecting the eaeA gene at lower concentrations than the PCR-LS-50B procedur e, regardless of the meat type or enrichment medium. Escherichia coli O157: H7 spiked at 0.3 CFU/mL was detectable after 9 h in EEB, but it was not det ected in mECB within 24 h. An enrichment time of 4 h in mECB was needed to detect E. coli O157:H7 when spiked at higher levels (41 CFU/mL). ne detecti on levels reported in this study are similar with other reported PCR-based detection techniques for E. coli O157:H7, however, the 5' nuclease-based as says are less labor intensive and capable of higher sample throughput becau se of their automated detection and analysis steps.