title: Multinational outbreak of travel-related Salmonella Chester infections in Europe, summers 2014 and 2015.
abstract: Between 2014 and 2015, the European Centre for Disease Prevention and Control was informed of an increase in numbers of Salmonella enterica serotype Chester cases with travel to Morocco occurring in six European countries. Epidemiological and microbiological investigations were conducted. In addition to gathering information on the characteristics of cases from the different countries in 2014, the epidemiological investigation comprised a matched case-case study involving French patients with salmonellosis who travelled to Morocco that year. A univariate conditional logistic regression was performed to quantify associations. The microbiological study included a whole genome sequencing (WGS) analysis of clinical and non-human isolates of S. Chester of varied place and year of isolation. A total of 162 cases, mostly from France, followed by Belgium, the Netherlands, Spain, Denmark and Sweden were reported, including 86 (53%) women. The median age per country ranged from 3 to 38 years. Cases of S. Chester were more likely to have eaten in a restaurant and visited the coast of Morocco. The results of WGS showed five multilocus sequence types (ST), with 96 of 153 isolates analysed clustering into a tight group that corresponded to a novel ST, ST1954. Of these 96 isolates, 46 (48%) were derived from food or patients returning from Morocco and carried two types of plasmids containing either qnrS1 or qnrB19 genes. This European-wide outbreak associated with travel to Morocco was likely a multi-source outbreak with several food vehicles contaminated by multidrug-resistant S. Chester strains.
authors.affiliation: Santé publique France, the French national public health agency, Saint-Maurice, France.|European Programme for Intervention Epidemiology Training (EPIET), European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden.
authors.forename: Laure
authors.initials: L
authors.lastname: Fonteneau
authors.affiliation: Santé publique France, the French national public health agency, Saint-Maurice, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Jourdan Da Silva
authors.affiliation: Institut Pasteur, French National Reference Center for E. coli, Shigella and Salmonella, Paris, France.
authors.forename: Laetitia
authors.initials: L
authors.lastname: Fabre
authors.affiliation: Public Health England, Gastrointestinal Bacterial Reference Unit, London, England.
authors.forename: Philip
authors.initials: P
authors.lastname: Ashton
authors.affiliation: Statens Serum institut (SSI), Denmark.
authors.forename: Mia
authors.initials: M
authors.lastname: Torpdahl
authors.affiliation: Statens Serum institut (SSI), Denmark.
authors.forename: Luise
authors.initials: L
authors.lastname: Müller
authors.affiliation: Institut Pasteur du Maroc, Sécurité alimentaire et environnement, Casablanca, Morocco.
authors.forename: Brahim
authors.initials: B
authors.lastname: Bouchrif
authors.affiliation: University Ibn Zohr, LBVRN, Agadir, Morocco.
authors.forename: Abdellah
authors.initials: A
authors.lastname: El Boulani
authors.affiliation: NRL Salmonella & AMR, Veterinary Laboratory of Chalkida, Greece.
authors.forename: Eleni
authors.initials: E
authors.lastname: Valkanou
authors.affiliation: NRL Salmonella, Institute of Public Health, Belgium.
authors.forename: Wesley
authors.initials: W
authors.lastname: Mattheus
authors.affiliation: Netherlands National Institute for Public Health and the Environment (RIVM), the Netherlands.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Friesema
authors.affiliation: National Center for Microbiology. Instituto de Salud Carlos III, Spain.
authors.forename: Silvia
authors.initials: S
authors.lastname: Herrera Leon
authors.affiliation: Instituto de Salud Carlos III, CIBER Epidemiología y Salud Pública (CIBERESP), Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Varela Martínez
authors.affiliation: Laboratoire National de Santé, Luxembourg.
authors.forename: Joël
authors.initials: J
authors.lastname: Mossong
authors.affiliation: European Centre for Disease Prevention and Control, Stockholm, Sweden.
authors.forename: Ettore
authors.initials: E
authors.lastname: Severi
authors.affiliation: Public Health England, Gastrointestinal Bacterial Reference Unit, London, England.
authors.forename: Kathie
authors.initials: K
authors.lastname: Grant
authors.affiliation: Institut Pasteur, French National Reference Center for E. coli, Shigella and Salmonella, Paris, France.
authors.forename: François-Xavier
authors.initials: FX
authors.lastname: Weill
authors.affiliation: European Centre for Disease Prevention and Control, Stockholm, Sweden.|School of Public Health and Primary Care (CAPHRI), Maastricht University Medical Center (MUMC+), Maastricht, the Netherlands.
authors.forename: Céline M
authors.initials: CM
authors.lastname: Gossner
authors.affiliation: NRL Salmonella, Institute of Public Health, Belgium.
authors.forename: Sophie
authors.initials: S
authors.lastname: Bertrand
authors.affiliation: Public Health England, Gastrointestinal Bacterial Reference Unit, London, England.
authors.forename: Tim
authors.initials: T
authors.lastname: Dallman
authors.affiliation: Institut Pasteur, French National Reference Center for E. coli, Shigella and Salmonella, Paris, France.
authors.forename: Simon
authors.initials: S
authors.lastname: Le Hello
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D005060:Europe / Q000453:epidemiology; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D009018:Morocco; D058885:Multilocus Sequence Typing; D010802:Phylogeny; D010957:Plasmids; D012478:Salmonella Food Poisoning / Q000453:epidemiology* / Q000382:microbiology; D012480:Salmonella Infections / Q000175:diagnosis / Q000453:epidemiology* / Q000382:microbiology; D019779:Salmonella enterica / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D065288:Serogroup; D014195:Travel; D055815:Young Adult
keywords: Morocco; Salmonella; WGS; case-case study; outbreak; serotype Chester