Evaluation of the VTEC-screen "Seiken" test for detection of different types of Shiga toxin (verotoxin)-producing Escherichia coli (STEC) in human stool samples

An immunoassay for in vitro detection of Shiga (Vero) toxins Stx1 and Stx2 (VTEC-Screen "Seiken") was compared with the verocell toxicity test (VCA) and an stx-gene specific PCR for detection of Shiga toxin-producing E. coli (STEC) from 234 human stool samples selectively enriched on sorbitol-MacConkey (SMAC) agar. Culturable STEC were isolated from 59 (25.2%) of the 234 stool specimens and were found to be distributed over 20 different O-serogroups. Fifty-three (89.8%) of the 59 STEC-positive samples were identified with the VTEC-Screen compared to 55 (93.2%) with the PCR and 58 (98.3%) with the VCA. A possible false positive reaction with the VTEC-Screen was obtained with one sample and five samples showed aspecific reactions with both the test- and the control latex. The VTEC-Screen detected all samples which contained Stx1 producing strains (77.9% of STEC-positive samples) but was negative with six samples (10.2%) which contained Stx2 and/or Stx2 variant producers, although secondary enrichment of on brain-heart infusion agar detected three of these to improve the detection rate to 94.9%. Examination of reference strains encoding different genotypes of stx(1) and stx(2) indicated that certain variants of Stx2 reacted poorly (Stx2d-Ount, Stx2e and Stx2ev) or not at all with the VTEC-Screen. Overall, however, the test was found to be accurate, rapid and easy to perform, thus being suitable for the routine screening of clinical stool specimens for STEC. (C) 2002 Elsevier Science Inc. All rights reserved.