Laboratory Investigation ofa Multistate Food-Borne Outbreak ofEscherichia coli 0157:H7 byUsing Pulsed-Field Gel Electrophoresis andPhageTyping

strains. ThePFGE patterns of sevenpreoutbreak sporadic isolates andfive sporadic isolates fromtheoutbreak period differed fromthatof theoutbreak strain bya single band,making itdifficult toidentify these isolates asoutbreak ornon-outbreak related. Phagetyping andPFGEwithadditional enzymes werehelpful inresolving this problem. Whilenotas sensitive asPFGE,phagetyping was helpful ininterpreting PFGEdataandcould havebeenusedas asimple, rapid screentoeliminate theneedforperforming PFGEon unrelated isolates.