Molecular epidemiology of escherichia coli 0157:H7 strains by bacteriophage a 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 0157:H7 were analyzed for restriction fragment length polymorphisms on Southern blots probed with bacteriophage A DNA. The isolates analyzed included strains from a recent large multistate outbreak of E. coli 0157:H7 infection associated with consumption of poorly cooked beef in restaurants, a day-care center cluster, and temporally and geographically unrelated isolates. E. coli 0157:H7 isolates recovered from the incriminated meat and from 61 (96.8%) of 63 patients from Washington and Nevada possessed identical A restriction fragment length patterns. The A restriction fragment length polymorphisms observed in 11 (91.7%) of 12 day-care center patients were identical, but they differed from that of the strain associated with the multistate outbreak. E. coli 0157:H7 from 42 patients temporally or geographically unrelated to either cluster of infection possessed unique and different A restriction fragment length patterns, except for paired isolates from three separate clusters of infection. These data demonstrate that the hybridization of DNA digests of E. coli 0157:H7 with radiolabelled bacteriophage K DNA can be a useful, stable, and discriminatory epidemiologic tool for analyzing the linkage between strains of E. coli 0157:H7.