title: Multistate outbreak of Listeria monocytogenes infections linked to whole apples used in commercially produced, prepackaged caramel apples: United States, 2014-2015.
abstract: Whole apples have not been previously implicated in outbreaks of foodborne bacterial illness. We investigated a nationwide listeriosis outbreak associated with caramel apples. We defined an outbreak-associated case as an infection with one or both of two outbreak strains of Listeria monocytogenes highly related by whole-genome multilocus sequence typing (wgMLST) from 1 October 2014 to 1 February 2015. Single-interviewer open-ended interviews identified the source. Outbreak-associated cases were compared with non-outbreak-associated cases and traceback and environmental investigations were performed. We identified 35 outbreak-associated cases in 12 states; 34 (97%) were hospitalized and seven (20%) died. Outbreak-associated ill persons were more likely to have eaten commercially produced, prepackaged caramel apples (odds ratio 326·7, 95% confidence interval 32·2-3314). Environmental samples from the grower's packing facility and distribution-chain whole apples yielded isolates highly related to outbreak isolates by wgMLST. This outbreak highlights the importance of minimizing produce contamination with L. monocytogenes. Investigators should perform single-interviewer open-ended interviews when a food is not readily identified.
authors.affiliation: Centers for Disease Control and Prevention,Atlanta,GA,USA.
authors.forename: K M
authors.initials: KM
authors.lastname: Angelo
authors.affiliation: Centers for Disease Control and Prevention,Atlanta,GA,USA.
authors.forename: A R
authors.initials: AR
authors.lastname: Conrad
authors.affiliation: Minnesota Department of Health,St. Paul,MN,USA.
authors.forename: A
authors.initials: A
authors.lastname: Saupe
authors.affiliation: Arizona Department of Health Services,Phoenix,AZ,USA.
authors.forename: H
authors.initials: H
authors.lastname: Dragoo
authors.affiliation: New Mexico Department of Health,Santa Fe,NM,USA.
authors.forename: N
authors.initials: N
authors.lastname: West
authors.affiliation: Minnesota Department of Agriculture,St. Paul,MN,USA.
authors.forename: A
authors.initials: A
authors.lastname: Sorenson
authors.affiliation: California Department of Public Health Food and Drug Branch,Sacramento,CA,USA.
authors.forename: A
authors.initials: A
authors.lastname: Barnes
authors.affiliation: Food and Drug Administration,College Park,MD,USA.
authors.forename: M
authors.initials: M
authors.lastname: Doyle
authors.affiliation: Food and Drug Administration,College Park,MD,USA.
authors.forename: J
authors.initials: J
authors.lastname: Beal
authors.affiliation: Centers for Disease Control and Prevention,Atlanta,GA,USA.
authors.forename: K A
authors.initials: KA
authors.lastname: Jackson
authors.affiliation: Centers for Disease Control and Prevention,Atlanta,GA,USA.
authors.forename: S
authors.initials: S
authors.lastname: Stroika
authors.affiliation: Centers for Disease Control and Prevention,Atlanta,GA,USA.
authors.forename: C
authors.initials: C
authors.lastname: Tarr
authors.affiliation: Centers for Disease Control and Prevention,Atlanta,GA,USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Kucerova
authors.affiliation: Centers for Disease Control and Prevention,Atlanta,GA,USA.
authors.forename: S
authors.initials: S
authors.lastname: Lance
authors.affiliation: Centers for Disease Control and Prevention,Atlanta,GA,USA.
authors.forename: L H
authors.initials: LH
authors.lastname: Gould
authors.affiliation: Centers for Disease Control and Prevention,Atlanta,GA,USA.
authors.forename: M
authors.initials: M
authors.lastname: Wise
authors.affiliation: Centers for Disease Control and Prevention,Atlanta,GA,USA.
authors.forename: B R
authors.initials: BR
authors.lastname: Jackson
mesh_terms: D002182:Candy / Q000382:microbiology; D002241:Carbohydrates; D004196:Disease Outbreaks; D005517:Foodborne Diseases / Q000453:epidemiology* / Q000382:microbiology; D005838:Genotype; D007407:Interviews as Topic; D008089:Listeria monocytogenes / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D008088:Listeriosis / Q000453:epidemiology* / Q000382:microbiology; D027845:Malus / Q000382:microbiology*; D058885:Multilocus Sequence Typing; D016019:Survival Analysis; D014481:United States / Q000453:epidemiology
chemical_list: D002241:Carbohydrates; C569050:caramel coloring
keywords:  Listeria ; Foodborne infections; food safety; infectious disease epidemiology; outbreaks