Development of a quantitative competitive PCR assay for detection and quantification of Escherichia coli O157:H7 cells.

A quantitative competitive PCR (QC-PCR) assay was developed to detect and quantify Escherichia coli O157:H7 cells. From 10(3) to 10(8) CFU of E. coli O157:H7 cells/ml was quantified in broth or skim milk, and cell densities predicted by QC-PCR were highly related to viable cell counts (r(2) = 0.99 and 0.93, respectively). QC-PCR has potential for quantitative detection of pathogenic bacteria in foods.