The prevalence of verocytotoxin-producing Escherichia coli (VTEC) and E. coli O157:H7 in beef in Sweden determined by PCR assays and an immuno-magnetic separation (IMS) method

• Published in: Food microbiology Vol. 15; no. 6; pp. 591 - 601
• Main Authors: LINDQVIST, R, ANTONSSON, A. K, NORLING, B, PERSSON, L, EKSTRÖM, A.-C. L, FÄGER, U, ERIKSSON, E, LÖFDAHL, S, NORBERG, P
• Format: Journal Article
• Language: English
• Published: London Elsevier 01.12.1998
• Subjects: Biological and medical sciences; Food industries; Fundamental and applied biological sciences. Psychology; Meat and meat product industries; Sweden; Europe; Polymerase chain reaction; Immunomagnetic method; Analysis method; Prevalence; Escherichia coli; Pathogenic; Meat product; Bacteria; Beef; Biological contamination; Enterobacteriaceae; Immunological method
• ISSN: 0740-0020; 1095-9998
• DOI: 10.1006/fmic.1998.0203

The number of cases of enterohaemorrhagic Escherichia coli (EHEC) in Sweden has increased dramatically since 1995, but no source of the infections has been identified. The prevalence of verocytotoxin-producing E. coli (VTEC), including E. coli O157:H7 in imported and domestic raw beef in Sweden, was determined by PCR assays and immuno-magnetic separation (IMS, Dynal). VTEC was detected by a multiplex PCR directed at sequences on the vt1 and vt2 genes, and the prevalence of E. coli O157:H7 was estimated by the IMS assay and a SZ-PCR which detects E. coli O157:H7 (and some strains of O157:NM, O55:H7 and O55:NM). VTEC was detected in 15.055% (57/368) and 1.051% (6/543) of the imported and domestic beef samples, respectively, by the multiplex PCR. E. coli O157:H7 was detected in 0.053% and 2.054% of the imported beef samples by the IMS and SZ-PCR assays, respectively. In domestic beef E. coli O157:H7 was not detected by either method, indicating that the occurrence in Swedish beef was less than 0.056% with a 95% certainty. The overall prevalence of VTEC was estimated to be 4.050%, by adjusting for the relative proportion of imported and domestic beef in Sweden and, similarly, the overall prevalence of E. coli O157:H7 was 0.0506% (IMS) or 0.055% (SZ-PCR). We propose that a useful strategy to analyse a large number of food samples for VTEC and E. coli O157:H7 is an initial screening of samples using the multiplex VT-PCR in conjunction with enrichment and buoyant density centrifugation, followed by further analyses on the fraction of VT-positive samples using either the IMS method or SZ-PCR. Copyright 1998 Academic Press.