Primers for Amplifying an Alanine Racemase Gene Fragment to Detect E. coli Strains in Foods

Specific oligonucleotide primers for detecting Escherichia coli in various foods were designed based upon the conserved sequences of the E. coli air gene from positions 322 to 345 and from 664 to 687. Bacteria and food samples were treated at 100°C for 10 min in 1% Tween 20 containing 5% NaCl and 1 mM EDTA, then used as templates for polymerase chain reaction (PCR). The oligonucleotide primers were specific to E. coli , except for Shigella species, when tested with 67 strains of E. coli , including such serotypes as O157:H7 and O111, and 32 strains of non‐ E. coli species. The oligonucleotide primers could prove useful for detecting E. coli in beef, chicken, pork, tomato, soybean, potato, cow's milk, and egg.