Long-term sentinel surveillance for enterotoxigenic Escherichia coli and Non-O157 Shiga toxin-producing E. coli in Minnesota

Background. Enterotoxigenic Escherichia coli (ETEC) and non-O157 Shiga toxin-producing E. coli (STEC) are not detected byconventional culture methods. The prevalence of ETEC infections in the United States is unknown, and recognized cases are primarilyassociated with foreign travel. Gaps remain in our understanding of STEC epidemiology.Methods. Two sentinel surveillance sites were enrolled: an urban health maintenance organization laboratory (Laboratory A)and a rural hospital laboratory (Laboratory B). Residual sorbitol MacConkey (SMAC) plates from stool cultures performed at LaboratoryA (1996-2006) and Laboratory B (2000-2008) were collected. Colony sweeps from SMAC plates were tested for genesencoding STEC toxins stx1 and stx2 (1996-2008) and ETEC heat-labile and heat-stable toxins eltB, estA 1, 2 and 3 (2000-2008)by polymerase chain reaction (PCR)-based assays.Results. In Laboratory A, a bacterial pathogen was identified in 7.0% of 21 970 specimens. During 1996-2006, Campylobacterwas the most common bacterial pathogen (2.7% of cultures), followed by Salmonella (1.2%), Shigella (1.0%), and STEC (0.9%).Among STEC (n = 196), O157 was the most common serogroup (31%). During 2000-2006, ETEC (1.9%) was the second most commonbacterial pathogen after Campylobacter (2.6%). In Laboratory B, of 19 293 specimens tested, a bacterial pathogen was identifiedfor 5.5%, including Campylobacter (2.1%), STEC (1.3%), Salmonella (1.0%), and ETEC (0.8%). Among STEC (n = 253), O157 wasthe leading serogroup (35%). Among ETEC cases, 61% traveled internationally.Conclusions. Enterotoxigenic E. coli and STEC infections were as common as most other enteric bacterial pathogens, and ETECmay be detected more frequently by culture-independent multiplex PCR diagnostic methods. A high proportion of ETEC cases weredomestically acquired.