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The frequency of molecular detection of virulence genes encoding cytolysin A, high-pathogenicity island and cytolethal distending toxin of Escherichia coli in cases of sudden infant death syndrome does not differ from that in other infant deaths and healthy infants

Amanda R. Highet^1,2, Anne M. Berry¹, Karl A. Bettelheim and Paul N. Goldwater^1,2

¹ Department of Microbiology and Infectious Diseases, SA Pathology, Women's and Children's Hospital, 72 King William Road, North Adelaide, South Australia, Australia

² University of Adelaide Discipline of Paediatrics, North Adelaide, South Australia, Australia

Correspondence
Amanda R. Highet
amanda.highet{at}adelaide.edu.au

Received July 24, 2008
Accepted November 10, 2008

Consistent pathological findings in sudden infant death syndrome (SIDS) are seen which display similarities to the pathogenesis of toxaemic shock and/or sepsis. A key candidate infectious agent that is possibly involved is Escherichia coli, given its universal early colonization of the intestinal tract of infants and an increased frequency of toxigenic and mouse-lethal isolates from SIDS compared with comparison infants. An explanation for these findings has yet to be identified. Using PCR, we screened E. coli isolates from 145 SIDS and 101 dead control and healthy infants for three new candidate pathogenicity-related genes: clyA (cytolysin A), irp2 [high-pathogenicity island (HPI)-specific gene] and cdt (cytolethal distending toxin). The results failed to show a positive correlation with SIDS, instead proving that clyA and irp2 genes were common to the infant intestinal E. coli. Interestingly we observed a high rate of carriage of these two potentially pathogenic genes in E. coli from healthy infants in the absence of diarrhoeal disease, and we report that in a number of cases, the detection of HPI-specific genes was predictable by serotype. Despite the lack of associations defined so far, there remains the likelihood that genetic determinants influence the interactions between E. coli and the host, so these factors may be part of the multi-factorial aspect of SIDS.

Abbreviations: APEC, avian pathogenic E. coli; CDT, cytolethal distending toxin; CNF, cytotoxic necrotizing factor; ETEC, enterotoxigenic E. coli; HPI, high-pathogenicity island; SIDS, sudden infant death syndrome; STEC, Shiga toxin-producing E. coli; UPEC, uropathogenic E. coli; VT+, verotoxigenic.

Present address: Flat 5, Rosedale Lodge, 220 Chase Side, London N14 4PH, UK (Retired).

A supplementary table and two supplementary figures are available with the online version of this paper.