Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 1, 2007
Publication Date: May 22, 2007
Citation: Uhlich, G.A. 2007. Characterization of Shiga toxin-producing Escherichia coli isolated from different sources. Meeting Abstract . Meeting Abstract. Technical Abstract: Recent food borne outbreaks of Shiga toxin-producing E. coli have been associated more frequently with environmentally contaminated produce rather than with meat products contaminated during slaughter. In this study we compared Shiga toxin-producing isolates from food, environmental and animal sources, and matched patient / product isolates for genetic and/or phenotypic differences in virulence, stress tolerance, and biofilm formation. Sixteen serotype O157:H7 isolates were positive by PCR for hly, eae, wyz, and either stx1, stx2 or both toxin genes. An E. coli serotype O-:H4 strain isolated from produce was negative for all genes except for stx1. Sequencing of the patient / product paired isolates indicated that, although all were PCR positive for stx2 but not stx1, all contained both stx2 and stx2c variant genes. The acid tolerance and heat inactivation profiles of all 17 strains were comparable except for a serotype O157:H7 calf isolate, which showed reduced heat and acid tolerance. Biofilm assays on glass coupons showed that the O-:H4 strain, but none of the serotype O157:H7 strains, formed a biofilm. However, in a mixed-strain biofilm study using the O-:H4 strain and a serotype O157:H7 strain isolated from the same container of produce, the O157:H7 strain showed increased persistence on glass when incubated in the presence of the O-:H4 strain. With the exception of the single calf isolate, there were no unexpected findings relative to the stress response or virulence potential of the other 16 isolates. This study also reports for the first time a possible cooperative mechanism for biofilm formation between a serotype O157:H7 strain and another E. coli displaying a different serotype.