Detection of verotoxin-producing Escherichia coli in stool specimens by the polymerase chain reaction

In this retrospective study a total of 404 stools kept at −70°C were tested for the presence of verotoxin-producing Escherichia coli (VTEC) by the polymerase chain reaction (PCR). Thirteen positive samples from 11 patients were identified by PCR which correlated with previous isolation of E. coli O157:H7. There was no failure to detect VTEC by PCR but PCR did not identify further VTEC isolates. We concluded that (a) the occurrence of VTEC other than serotype O157:H7 is rare in our demographic area, (b) PCR is effective in the identification of E. coli O157:H7, and (c) PCR has the additional advantage over conventional culture methods of identifying VTEC, including sorbitol-fermenting serotypes, which might have been detected if we had extended our sample size.