Enhanced surveillance of non-O157 verotoxin-producing Escherichia coli in human stool samples from Manitoba

Relatively few enhanced surveillance studies have been undertaken to investigate the extent to which verotoxin-producing non-O157 serotypes of Escherichia coli occur in stool samples received for the detection of verotoxin-producing organisms.

To describe the prevalence, molecular and epidemiological characteristics, and geographical patterns associated with non-O157 verotoxin-producing E coli (VTEC) in Manitoba.

Thirty-two VTEC isolates consisting of 10 serogroups and 13 different serotypes were isolated over a 22-month period. Twenty-three isolates (71.8%) possessed verotoxin-encoding gene stx1 only, five isolates (15.6%) possessed stx2 only, two isolates (6.3%) possessed both stx1 and stx2, and two isolates (6.3%) possessed stx2c. Only three instances of indistinguishable pulsed-field gel electrophoresis patterns were identified. The age of the individuals from whom non-O157 VTEC were isolated ranged from eight months to 87 years. Mean and median ages were 30 and 22 years of age, respectively. Some areas of the province appeared to experience a higher than expected number of non-O157 E coli in comparison with the number of stools that were received from these areas.

The present study demonstrated a large number of infections associated with non-O157 VTEC in Manitoba. Most non-O157 cases appear to result from sporadic infections, and these occur typically in rural areas. Continued enhanced surveillance is necessary to understand the temporal patterns of non-O157 VTEC and the underlying epidemiological factors driving these patterns.