Abstract:

Genomic comparisons were carried out on Escherichia coli virulence genes and genome-specific sequences, which were located in the genomes of Escherichia coli serotype O157:H7 strains released in the GenBank. One pair of primers specific for ECs3032 genes was exploited for the amplification to give a 292 bp PCR product. Conventional qualitative PCR and real-time quantitative PCR assays showed higher specificity of the primers. The assays were used for detecting Escherichia coli O157:H7 in ground beef initially inoculated at the dosages of 2, 20, or 200 CFU/mL after 2, 11, 16 h and 20 h of enrichment at 37 ℃ in modified EC broth. Escherichia coli O157:H7 was detected in all samples inoculated. The whole detection procedure was finished within 24 hours with a sensitivity of 2.0 CFU/mg beef sample using the PCR assay established in this study. Thus, an effective method is provided for the rapid PCR detection of Escherichia coli in foods.

Key words: enterohemorrhagic Escherichia coli O157:H7, foodborne pathogenic bacteria, specific sequence, PCR