MOLECULAR EPIDEMIOLOGY OF ESCHERICHIA-COLI O157-H7 STRAINS BY BACTERIOPHAGE-LAMBDA RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISM ANALYSIS - APPLICATION TO A MULTISTATE FOODBORNE OUTBREAK AND A DAY-CARE-CENTER CLUSTER

Genomic DNAs prepared from 168 isolates of Escherichia coli O157:H7 we re analyzed for restriction fragment length polymorphisms on Southern blots probed with bacteriophage lambda DNA. The isolates analyzed incl uded strains from a recent large multistate outbreak of E. coli 0157:H 7 infection associated with consumption of poorly cooked beef in resta urants, a day-care center cluster, and temporally and geographically u nrelated isolates. E. coli 0157:H7 isolates recovered from the incrimi nated meat and from 61 (96.8%) of 63 patients from Washington and Neva da possessed identical lambda restriction fragment length patterns. Th e lambda restriction fragment length polymorphisms observed in 11 (91. 7%) of 12 day-care center patients were identical, but they differed f rom that of the strain associated with the multistate outbreak. E. col i 0157:H7 from 42 patients temporally or geographically unrelated to e ither cluster of infection possessed unique and different lambda restr iction fragment length patterns, except for paired isolates from three separate clusters of infection. These data demonstrate that the hybri dization of DNA digests of E. coli 0157:H7 with radiolabelled bacterio phage lambda DNA can be a useful, stable, and discriminatory epidemiol ogic tool for analyzing the linkage between strains of E. coli 0157:H7 .