title: A multistate outbreak of Escherichia coli O157:H7 infections associated with consumption of mesclun lettuce.
abstract: BACKGROUND
  An outbreak of Escherichia coli O157:H7 infections in Connecticut and Illinois during May 28 to June 27, 1996, was investigated to determine the source of infections.
  
  
  METHODS
  Independent case-control studies were performed in both states. Pulsed-field gel electrophoresis (PFGE) was performed on E. coli O157:H7 isolates. A case-patient was defined as a Connecticut or northern Illinois resident with diarrhea whose stool culture yielded E. coli O157:H7 of the outbreak-associated PFGE subtype. Controls were town-, age-, and sex-matched to case-patients. We traced implicated lettuce to the farm level and performed environmental investigations to identify unsafe lettuce production practices.
  
  
  RESULTS
  In Connecticut and Illinois, infection was associated with consumption of mesclun lettuce (Connecticut matched odds ratio [MOR], undefined; 95% confidence interval [CI], 3.4 to infinity; and Illinois MOR, undefined; 95% CI, 1.4 to infinity). We traced implicated lettuce to a single grower-processor. Cattle, a known E. coli O157:H7 reservoir, were found near the lettuce fields. Escherichia coli (an indicator of fecal contamination) was cultured from wash water and finished lettuce. A trace-forward investigation identified 3 additional states that received implicated lettuce; E. coli O157:H7 isolates from patients in 1 of these states matched the outbreak-associated PFGE subtype.
  
  
  CONCLUSIONS
  This multistate outbreak of E. coli O157:H7 infections was associated with consumption of mesclun lettuce from a single producer. Molecular subtyping facilitated the epidemiological investigation. This investigation increased the knowledge about current production practices that may contribute to the contamination of lettuce by microbial pathogens. Lettuce production practices should be monitored for microbiological safety.
authors.affiliation: Epidemiology Program Office, Centers for Disease Control and Prevention, Atlanta, GA, USA. hilborn.e@epamail.epa.gov
authors.forename: E D
authors.initials: ED
authors.lastname: Hilborn
authors.forename: J H
authors.initials: JH
authors.lastname: Mermin
authors.forename: P A
authors.initials: PA
authors.lastname: Mshar
authors.forename: J L
authors.initials: JL
authors.lastname: Hadler
authors.forename: A
authors.initials: A
authors.lastname: Voetsch
authors.forename: C
authors.initials: C
authors.lastname: Wojtkunski
authors.forename: M
authors.initials: M
authors.lastname: Swartz
authors.forename: R
authors.initials: R
authors.lastname: Mshar
authors.forename: M A
authors.initials: MA
authors.lastname: Lambert-Fair
authors.forename: J A
authors.initials: JA
authors.lastname: Farrar
authors.forename: M K
authors.initials: MK
authors.lastname: Glynn
authors.forename: L
authors.initials: L
authors.lastname: Slutsker
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000822:Animal Husbandry; D000818:Animals; D002140:California / Q000453:epidemiology; D002417:Cattle; D002648:Child; D002675:Child, Preschool; D003237:Connecticut / Q000453:epidemiology; D004196:Disease Outbreaks; D004927:Escherichia coli Infections / Q000453:epidemiology* / Q000382:microbiology; D019453:Escherichia coli O157 / Q000302:isolation & purification; D005260:Female; D005431:Florida / Q000453:epidemiology; D005516:Food Microbiology; D006801:Humans; D007087:Illinois / Q000453:epidemiology; D018545:Lactuca / Q000382:microbiology*; D008297:Male; D008875:Middle Aged; D009518:New York / Q000453:epidemiology; D016017:Odds Ratio