Multistate outbreak of Escherichia coli O157:H7 infection associated with consumption of packaged spinach, August-September 2006: the Wisconsin investigation.

BACKGROUND: Escherichia coli O157:H7 infection often causes hemorrhagic colitis and hemolytic uremic syndrome. METHODS: In 2006, the Wisconsin Division of Public Health and the Wisconsin State Laboratory of Hygiene, in cooperation with other local, state, and federal partners, investigated an outbreak of E. coli O157:H7 infection. RESULTS: In September 2006, the Wisconsin Division of Public Health and the Wisconsin State Laboratory of Hygiene were able to link geographically dispersed E. coli O157:H7 isolates recovered from the stool samples of ill persons, all of which had the same pulsed-field gel electrophoresis pattern (i.e., outbreak pattern). Investigators conducted a case-control study with control subjects (n = 86) matched to case patients (n = 49) by age, sex, and residential location. All case patients' onsets of illness occurred during the period from 20 August through 14 September 2006. Illness was associated with spinach consumption (matched odds ratio, 82.1; 95% confidence interval, 14.7 to >1000). Of the 49 case patients, 26 (53%) recalled eating brand A spinach. On multibrand analysis, only brand A was associated with illness (undefined matched odds ratio; 95% confidence interval, 6.8-infinity). Wisconsin's agriculture laboratory isolated E. coli O157:H7 with the outbreak pattern from spinach in 2 brand A packages, both produced on 15 August 2006. CONCLUSIONS: The rapid multijurisdictional epidemiologic and laboratory response, including timely pulsed-field gel electrophoresis pattern analysis and PulseNet posting, facilitated prompt voluntary recall of brand A spinach.

Four strains of Escherichia coli O157:H7 isolated from patients during an outbreak of disease associated with ground beef: importance of evaluating multiple colonies from an outbreak-associated product.

This report describes the investigation of a ground-beef-associated outbreak that involved five genetically distinct patient strains of Escherichia coli O157:H7. Human and product isolates were evaluated by pulsed-field gel electrophoresis (PFGE) with two endonucleases. The multiple-strain etiology of this outbreak underscores the importance of isolating and evaluating multiple colonies from outbreak-related products and comparing two endonuclease PFGE patterns of all product and human isolates identified during outbreak periods. This investigation emphasizes the importance of interviewing all confirmed and suspected case patients during the outbreak period, regardless of the PFGE pattern of their isolate, to confirm or rule out an epidemiologic link to the outbreak.