EVALUATION OF AN ALANINE RACEMASE GENE AS AN INDICATOR FOR THE DETECTION OF VARIOUS ESCHERICHIA-COLI - REACTIVITY OF THE GENE FRAGMENT WITHVARIOUS ESCHERICHIA-COLI O157-H7 ISOLATES

We determined whether various Escherichia coli O157:H7 isolates could be detected using a probe, an alanine racemase gene (dadX) fragment, s pecific to E. coil. One hundred strains of E. coil O157:H7 were isolat ed from fecal samples of healthy cattles and human patients with diarr hea and from a leg of beef. Most isolates (95 strains) produced both v erocytotoxin 1 (VT1, Shiga-like toxin I) and verocytotoxin 2 (VT2, Shi ga-like toxin II), whereas four isolates produced only VT2. Although n either VT1 nor VT2 was detected in one isolate under the conditions us ed, the VT2 gene was detected. When all of the isolates were analyzed by a DNA hybridization method involving the use of the probe, positive signals were obtained from all isolates. The DNA hybridization method used for detection of E. coil is considered to detect various E. coli O157:H7 isolates which differ in the types of verocytotoxin they prod uce.