Evaluation of a 5'-Nuclease PCR Assay for the Detection of Escherichia coli O157 in Pure Culture and Foods

Abstract

We evaluated the ability of the 5'-nuclease (TaqMan) PCR assay by Commercial Detection Kit to detect Shigatoxin-producing Escherichia coli O157 in pure cultures, inoculated raw ground meat, shrimp and vegetable enrichment samples. The results were compared with the culture method, standard PCR assay and ELISA. The TaqMan PCR was able to identify the organism when 10² cfu/ml or more organisms were present in pure culture and in novobiocin-modified EC enrichment of several food samples.
In comparison, the recovery efficiency on CTSMAC plate was from 10¹ to 10⁶ cfu/ml, standard PCR assay sensitivity was 10⁴ cfu/ml or more organisms, and ELISA test showed false positive in contaminated samples of Citrobacter freundii. Our findings indicate that TaqMan PCR assay is a useful automatic assay for identifying the existence of E. coli O157 in food samples with a high detection sensitivity and results in two days.