Laboratory-based surveillance of human verocytotoxigenic Escherichia coli infection in the Republic of Ireland, 2002-2004.

The aim of this study was to examine the frequency and distribution of human verocytotoxigenic Escherichia coli (VTEC) O157 and non-O157 in the Republic of Ireland, and also to examine the presence of virulence genes in these isolates. This genetic information combined with phenotypic tests was used to produce a complete laboratory-based surveillance of human clinical VTEC infection in the Republic of Ireland between 2002 and 2004. Between January 2002 and December 2004 a total of 207 VTEC isolates were studied (one isolate per patient), 185 (89 %) of these were E. coli O157. The remaining 22 (11 %) were non-O157 E. coli, made up of 15 (7.2 %) E. coli O26, one (0.5 %) E. coli O103, one (0.5 %) E. coli O146, one (0.5 %) E. coli O145, two (1 %) E. coli O111 and two (1 %) ungroupable VTEC. These isolates originated from the eight health boards in the Republic of Ireland and represented over 90 % of the clinical cases of VTEC in the Republic of Ireland during this period. The results showed that VTEC O157 was the predominant serogroup and had a predominant toxin genotype of VT2 alone. Phage type 32 was the most common phage type of E. coli O157 identified. Non-O157 VTEC was a small proportion of all VTEC (10 % in 2002, 8 % in 2003, 15.5 % in 2004). In 2004 it was noted that there was an increase in the number and variety of non-O157 VTEC strains; however, this requires further monitoring in the future to see if this trend is sustained. It was also noted throughout the study period that the incidence of VTEC was higher in rural areas. Implementation of real-time PCR for the detection and subtyping of VTEC has aided outbreak investigations and is important for enhanced surveillance of VTEC in the Republic of Ireland.