title: Epidemiological and Microbiological Investigation of an Outbreak of Severe Disease from Shiga Toxin-Producing Escherichia coli O157 Infection Associated with Consumption of a Slaw Garnish.
abstract: Investigating outbreaks of Shiga toxin-producing Escherichia coli (STEC) in England is a priority due to the potential severity of disease. However, there are often challenges in investigating outbreaks due to the small numbers of cases, poor patient recall, and low levels of bacteria that are challenging to detect in food samples using traditional laboratory culture techniques, and frequently a source is not identified. In September 2014, we investigated an STEC O157 outbreak associated with consuming a slaw garnish, and we report our findings here. Twenty confirmed cases were identified. Outbreak cases were interviewed, and menus reviewed to identify dishes consumed outside the home. Cases shared a history of eating meals at different chain restaurants. Analysis of menu items indicated shared consumption of slaw garnishes by 85.6% cases, although just 35.7% reported consuming them during interviews. Whole-genome sequencing linked cases where interpretation of the multilocus variable number tandem repeat analysis profile was obscured and indicated that the strain originated from a domestic (i.e., United Kingdom) source. Traceback identified that carrots and cabbages grown in the United Kingdom were the likely source of infection. Samples of products were examined, but STEC was not recovered. Epidemiological investigations linked the outbreak to consumption of a slaw garnish, which was poorly recalled by cases, and likely comprised of domestically produced raw vegetables. The causative organism was not isolated from food samples, and we conclude that future investigations should include sampling of animals and wildlife in the vicinity of farms where implicated produce is grown.
authors.affiliation: Gastrointestinal Illness Department, National Infections Service, Public Health England, 61 Colindale Avenue, London, NW9 5EQ, UK. lisa.byrne@phe.gov.uk.
authors.forename: Lisa
authors.initials: L
authors.lastname: Byrne
authors.affiliation: Gastrointestinal Illness Department, National Infections Service, Public Health England, 61 Colindale Avenue, London, NW9 5EQ, UK; Gastrointestinal Bacteria Reference Unit, National Infections Service, Public Health England, 61 Colindale Avenue, London, NW9 5EQ, UK; National Institute for Health Research (NIHR) Health Protection Research Unit in Gastrointestinal Infections, Public Health England, 61 Colindale Avenue, London, NW9 5EQ, UK; National Institute for Health Research (NIHR) Health Protection Research Unit in Gastrointestinal Infections, University of Liverpool, Liverpool, L69 7BE, UK.
authors.forename: Natalie
authors.initials: N
authors.lastname: Adams
authors.affiliation: Gastrointestinal Illness Department, National Infections Service, Public Health England, 61 Colindale Avenue, London, NW9 5EQ, UK.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Glen
authors.affiliation: Gastrointestinal Bacteria Reference Unit, National Infections Service, Public Health England, 61 Colindale Avenue, London, NW9 5EQ, UK.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Dallman
authors.affiliation: Wessex Public Health England Centre, Solent Business Park, Unit 8, Victory Park, Fareham, PO15 7FN, UK.
authors.forename: Ishani
authors.initials: I
authors.lastname: Kar-Purkayastha
authors.affiliation: Anglia Health Protection Team, Anglia and Essex Public Health England Centre, Public Health England, Thetford Community Healthy Living Centre, Croxton Road, Thetford, IP24 1JD, UK.
authors.forename: Gillian
authors.initials: G
authors.lastname: Beasley
authors.affiliation: Food, Water and Environment Laboratory, Public Health England, Manor Farm Road, Porton Down, Salisbury, SP4 0JG, UK.
authors.forename: Caroline
authors.initials: C
authors.lastname: Willis
authors.affiliation: Public Health England Centre Yorkshire and Humber, York Block 2, The Food and Environment Research Agency (FERA), Sand Hutton, York, YO41 1LZ, UK.
authors.forename: Simon
authors.initials: S
authors.lastname: Padfield
authors.affiliation: Gastrointestinal Illness Department, National Infections Service, Public Health England, 61 Colindale Avenue, London, NW9 5EQ, UK.
authors.forename: Goutam
authors.initials: G
authors.lastname: Adak
authors.affiliation: Gastrointestinal Bacteria Reference Unit, National Infections Service, National Institute for Health Research (NIHR) Health Protection Research Unit in Gastrointestinal Infections, Public Health England, 61 Colindale Avenue, London, NW9 5EQ, UK.
authors.forename: Claire
authors.initials: C
authors.lastname: Jenkins
mesh_terms: D000818:Animals; D004196:Disease Outbreaks; D004739:England; D004927:Escherichia coli Infections / Q000382:microbiology*; D019453:Escherichia coli O157 / Q000302:isolation & purification; D005516:Food Microbiology; D006801:Humans; D054323:Shiga-Toxigenic Escherichia coli / Q000302:isolation & purification*; D006113:United Kingdom