SURVEILLANCE FOR ESCHERICHIA-COLI O157-H7 INFECTIONS IN MINNESOTA BY MOLECULAR SUBTYPING

Background Escherichia coli O157:H7 is a leading cause of diarrhea and the hemolytic-uremic syndrome. Current public health surveillance for E. coli O157:H7 requires considerable resources; traditional methods lack the sensitivity and specificity to detect outbreaks effectively. Methods During 1994 and 1995, the Minnesota Department of Health reque sted that all clinical isolates of E. coli O157:H7 be submitted to our laboratory. Isolates were subtyped by pulsed-field gel electrophoresi s (PFGE), and patients were interviewed about potential sources of inf ection. Results In 1994 and 1995, 344 cases of E. coli O157:H7 infecti on were reported to the Minnesota Department of Health; 317 (92 percen t) were subtyped by PFGE, and 143 distinct PFGE patterns were identifi ed. Ten outbreaks of E. coli O157:H7 were identified; these accounted for 56 (18 percent) of the 317 subtyped cases, Four outbreaks were det ected solely as a result of subtype-specific surveillance. In 11 two-w eek periods, the number of reported cases of E. coli O157:H7 doubled f rom the previous two weeks. In eight of these instances, the patterns identified were dissimilar and there were no outbreaks. Two of the rem aining three increases resulted from multiple simultaneous outbreaks. Conclusions Subtype-specific surveillance for E. coli O157:H7 can iden tify outbreaks that are not detected by traditional methods and can as certain whether sudden increases in reported cases are due to sporadic isolated cases or to one or more outbreaks. (C) 1997, Massachusetts M edical Society.