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. 2017 Feb 16;22(7):30463.
doi: 10.2807/1560-7917.ES.2017.22.7.30463.

Multinational outbreak of travel-related Salmonella Chester infections in Europe, summers 2014 and 2015

Laure Fonteneau  1   2 , Nathalie Jourdan Da Silva  1 , Laetitia Fabre  3 , Philip Ashton  4 , Mia Torpdahl  5 , Luise Müller  5 , Brahim Bouchrif  6 , Abdellah El Boulani  7 , Eleni Valkanou  8 , Wesley Mattheus  9 , Ingrid Friesema  10 , Silvia Herrera Leon  11 , Carmen Varela Martínez  12 , Joël Mossong  13 , Ettore Severi  14 , Kathie Grant  4 , François-Xavier Weill  3 , Céline M Gossner  14   15 , Sophie Bertrand  9 , Tim Dallman  4 , Simon Le Hello  3
Affiliations

Multinational outbreak of travel-related Salmonella Chester infections in Europe, summers 2014 and 2015

Laure Fonteneau et al. Euro Surveill. .

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.

Keywords: Morocco; Salmonella; WGS; case-case study; outbreak; serotype Chester.

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Conflict of interest statement

Conflict of interest: None declared.

Figures

Figure 1
Figure 1
Distribution of Salmonella Chester cases by respective isolate week and country of residence, European Union, 2014 (n = 162)
Figure 2
Figure 2
Phylogenetic tree of Salmonella enterica serotype Chester, European Union, 1937–2015 (n=153 isolates)
Figure 3
Figure 3
Maximum Likelihood phylogeny of the Salmonella Chester ST1954 strains, European Union (n=96 strains)
See this image and copyright information in PMC

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