An outbreak of Escherichia coli O157 : H7 infection from unpasteurized commercial apple juice

Background: Escherichia coli O157:H7 infections have traditionally been ass ociated with animal products, but outbreaks associated with produce have be en reported with increasing frequency. In fall 1996, a small cluster of E. coli O157:H7 infections was epidemiologically linked to a particular brand (brand A) of unpasteurized apple juice. Objective: To define the extent of the outbreak, confirm the source, and de termine how the apple juice became contaminated. Design: Descriptive epidemiologic study and traceback investigation. Setting: Western United States and British Columbia, Canada. Patients: Patients with E. coli O157:H7 infection who were exposed to brand A apple juice. Measurements: Clinical outcome and juice exposure histories of case-patient s, pulsed-field gel electrophoresis of case and juice isolates, and juice p roduction practices. Results: Seventy persons with E. coli O157:H7 infection and exposure to bra nd A unpasteurized apple juice were identified. Of these persons, 25 (36%) were hospitalized, 14 (20%) developed the hemolytic uremic syndrome, and 1 (1%) died. Recalled apple juice that was produced on 7 October 1996 grew E, coli O157:H7 with a pulsed-field gel electrophoresis pattern indistinguish able from that of case isolates. Apple juice produced on 7 October 1996 acc ounted for almost all of the cases, and the source of contamination was sus pected to be incoming apples. Three lots of apples could explain contaminat ion of the juice: Two lots originated from an orchard frequented by deer th at were subsequently shown to carry E. coli O157:H7, and one lot contained decayed apples that had been waxed. Conclusions: Standard procedures at a state-of-the-art plant that produced unpasteurized juices were inadequate to eliminate contamination with E. col i O157:H7. This outbreak demonstrated that unpasteurized juices must be con sidered a potentially hazardous food and led to widespread changes in the f resh juice industry.