The role of the genetic test of verotoxin for bacterial carrier investigation of cooking staff: detection of enterohemorrhagic Escherichia coli

The Ministry of Health, Labour and Welfare revised the Manual for Hygiene Management at Large-scale Food Preparation Facilities (Shokuan; Issue No. 0618005) on June 18, 2008. This manual was issued for the purpose of food poisoning prevention in mass food service facilities based on the concept of hazard analysis and critical control point(HACCP). Especially this revision of the manual made verotoxin(VT examination indispensable in the practice of regular fecal examination for cooking staff (stool examination). Out of 150 fecal specimens that were examined on May 12, 2009, a specimen from a dietician revealed a strain of enterohemorrhagic Escherichia coli EHEC O103: H2 producing type I verotoxin (VT1). We studied the following with regard to EHEC O103: H2 producing VT1(EHEC O103): colony forms of the bacteria on the selective media for EHEC as well as the differential media for VT in use for stool examination in the laboratory and the usefulness of the hospital PCR based detection of VT genes. CHROMagar O26/O157 agar plates were used to select and isolate EHEC. Enterohemolysin blood agar plates were used to confirm VT. Polymerase chain reaction (PCR) was conducted using primers set EVT-1, 2 as well as EVS-1, 2. CHROMagar O26/O157 agar plates and enterohemolysin blood agar plates can distinguish EHEC strains easily, rapidly, and effectively, although not always correctly. The PCR method employs PCR technology targeting VT genes, so that it can verify VT genes in all strains of E. coli. This examination is useful for defining EHEC especially in stool examinations of asymptomatic patients. The PCR-based detection of VT genes was considered as a rational method for fecal examination compatible with the revised Manual for Hygiene Management at Large-scale Food Preparation Facilities.