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Prevalence of Shiga toxin-producing and enteropathogenic Escherichia coli marker genes in diarrhoeic stools in a New Zealand catchment area
  1. Rowan R Thomas1,
  2. Heather J L Brooks1,
  3. Rory O'Brien2
  1. 1Department of Microbiology and Immunology, University of Otago, Dunedin, Otago, New Zealand
  2. 2Disease Research Laboratory, Department of Microbiology and Immunology, University of Otago, Dunedin, Otago, New Zealand
  1. Correspondence to Rowan R Thomas, Department of Microbiology and Immunology, University of Otago, PO Box 56, 720 Cumberland St, Dunedin, Otago 9016, New Zealand; rthomas726{at}


Background Shiga toxin-producing (STEC) and enteropathogenic (EPEC) Escherichia coli are gastrointestinal pathogens causing diarrhoeal and extraintestinal disease. Due to lack of EPEC screening and use of Sorbitol-MacConkey (SMAC) agar in faecal screening, the true prevalence of EPEC and non-O157 STEC in New Zealand diarrhoeal cases is unknown.

Methods Diarrhoeic stools sourced from Dunedin hospital were pre-enriched, DNA extracted with Chelex-100 resin and screened using a multiplex TaqMan quantitative PCR assay amplifying stx1, sxt2 and EPEC (eae) gene markers.

Results Of the 522 diarrhoeic samples surveyed, 8 (1.53%) were PCR positive for stx1/stx2 and 23 (4.41%) were positive for eae. Six (75%) of the stx+ samples were uncommon non-O157 serotypes, and the remainder were found to be positive for both O103 and O157 STEC somatic antigens.

Conclusions Results revealed shortcomings in current screening protocols for pathogenic E. coli; SMAC is not sufficiently discriminatory to detect emergent STEC serotypes and EPEC likely has an unappreciated role in cases of diarrhoea in New Zealand.

  • E COLI
  • PCR

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  • Handling editor Slade Jensen

  • Contributors RRT completed sample screening procedures, data analysis, interpretation, research and drafting of manuscript. HJLB and RO contributed to study design, supervision, data interpretation and manuscript editing.

  • Funding Many thanks to the University of Otago (Master's Scholarship) and the Dunedin Basic Medical Sciences Course Trust (Sandy Smith Scholarship).

  • Competing interests None declared.

  • Ethics approval Obtained from Otago University Human Ethics Committee, in accordance with the New Zealand Human Tissues Act 2008 and the New Zealand Health Information Privacy Code 1994.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement Unpublished data may be available on an individual request basis.