Shiga toxin-producing Escherichia coli carrying stx2f as an emerging cause of diarrhoea in the Netherlands

Abstract number: O362

Schuurman T., Roovers A., van der Zwaluw W.K., van Zwet A.A., Sabbe L.J.M., Kooistra-Smid A.M.D., van Duynhoven Y.T.H.P.

Objectives: Shiga toxin-producing Escherichia coli (STEC) that carry the stx2f gene are considered to be host-adapted to pigeons, and therefore of limited clinical relevance to humans. In fact, to date only 6 cases have been documented in the recent literature (1990–2007), and with the exception of a single case, all have been linked with uncomplicated diarrhoea. Due to this low incidence, routine diagnostic procedures have not been adapted to detect this variant. In this study we investigated the possible role of stx2f-carrying STEC in the aetiology of diarrhoea.

Methods: A total of 2155 stool specimens, for which routine screening for gastrointestinal pathogens was requested, were analysed between September 2006 and March 2007. DNA was extracted from the specimens using the NucliSENS easyMAG specific A protocol. STEC were detected by internally controlled multiplex real-time PCR (Schuurman et al J Microb Meth 2007:406–415) adapted for detection of the stx1c, stx1d, and stx2f genes. Positive specimens were partially subtyped using the monoplex real-time PCRs to identify stx1, stx1c, stx1d, stx2f, and the group containing stx2, stx2c, stx2d, stx2e, and stx2g (stx2cdeg). Isolation of STEC strains was performed from stx2f positive specimens by culture on sorbitol MacConkey agar and colony screening by PCR.

Results: A total of 37 specimens showed STEC specific amplification signals. Subtyping was successful in 35 of 37 specimens, and revealed stx2f (n = 4) as the third most prevalent genotype after stx2cdeg (n = 13) and stx1 (n = 6). Other genotypes detected included stx1 + stx1c (n = 2), stx1c (n = 2), stx1 + stx2cdeg (n = 1), and stx1/stx1c + stx2cdeg (n = 1). Patients positive for stx2f had uncomplicated diarrhoea (n = 2) and bloody diarrhoea (BD) (n = 2), although the BD could also be explained by co-infection/morbidity these patients. Isolation of an STEC strain was successful in 2/4 stx2f-positive specimens, and yielded an O63:H6 serotype, eae gene (intimin) positive in both cases. Both strains were also shown to be highly related based on pulsed field gel electrophoresis, although no epidemiological link was apparent between both patients.

Conclusions: STEC that carry the stx2f gene were the third most prevalent stx-genotype in The Netherlands during the study. Our results suggest that stx2f-carrying STEC may be an overlooked cause of diarrhoea. Diagnostic screening strategies need to be adapted to detect this variant in the routine diagnostic laboratory.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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