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Keywords:

  • beef;
  • shiga toxin-producing Escherichia coli;
  • STEC ;
  • serotypes;
  • virulence factors;
  • virulotypes

Abstract

Aims

To assess the prevalence of Shiga toxin-producing Escherichia coli (STEC) on a cluster of twelve beef farms in the north-east of Ireland.

Methods and Results

Samples were screened for stx1 and stx2 using PCR. Positive samples were enriched in mTSB and STEC O157 isolated using immunomagnetic separation. Enrichment cultures were plated onto TBX agar to isolate non-O157 STEC. All isolates were serotyped and examined for a range of virulence genes and their antibiotic resistance phenotype determined. Eighty-four isolates of 33 different serotypes were cultured from the 13·7% of samples that were stx positive. The most prevalent serotype was O157:H7, the most common Shiga toxin was stx2, and a variety of virulence factor combinations was observed. O-:H-, O26:H11, O76:H34, O157:H7, O157:H16 and OX18:H+ also carried eaeA and hlyA genes. Twenty-nine per cent of strains were resistant to at least one antibiotic, 48% of which had multiple drug resistance (MDR) with O2:H32 displaying resistance to five antibiotics.

Conclusions

The ubiquitous nature of STEC on beef farms, the detection of stx+ eaeA+ hlyA+ in the serotypes O-:H-, O157:H16 and OX18:H+ in addition to O157:H7 and O26:H11 and the widespread distribution of antibiotic resistance are of public health concern as new virulent STEC strains are emerging.

Significance and Impact of the Study

This study found no relationship between serotype and antibiotic resistance, therefore negating efforts to isolate serotypes using specific antibiotic supplemented media. The data presented provide further evidence of the emergence of new STEC virulotypes of potential public health significance.