Disentangling a complex nationwide Salmonella Dublin outbreak associated with raw-milk cheese consumption, France, 2015 to 2016

Abstract

On 18 January 2016, the French National Reference Centre for Salmonella reported to Santé publique France an excess of Salmonella enterica serotype Dublin (S. Dublin) infections. We investigated to identify the source of infection and implement control measures. Whole genome sequencing (WGS) and multilocus variable-number tandem repeat analysis (MLVA) were performed to identify microbiological clusters and links among cases, animal and food sources. Clusters were defined as isolates with less than 15 single nucleotide polymorphisms determined by WGS and/or with identical MLVA pattern. We compared different clusters of cases with other cases (case–case study) and controls recruited from a web-based cohort (case–control study) in terms of food consumption. We interviewed 63/83 (76%) cases; 2,914 controls completed a questionnaire. Both studies’ findings indicated that successive S. Dublin outbreaks from different sources had occurred between November 2015 and March 2016. In the case–control study, cases of distinct WGS clusters were more likely to have consumed Morbier (adjusted odds ratio (aOR): 14; 95% confidence interval (CI): 4.8–42) or Vacherin Mont d’Or (aOR: 27; 95% CI: 6.8–105), two bovine raw-milk cheeses. Based on these results, the Ministry of Agriculture launched a reinforced control plan for processing plants of raw-milk cheeses in the production region, to prevent future outbreaks.

Source Attribution Study of Sporadic Salmonella Derby Cases in France

“…The 299 human strains corresponding to all the clinical cases that occurred in metropolitan France in 2014 and 2015 were collected by the National Reference Center (NRC) (Institut Pasteur). These strains were identified as serovar Derby by glass slide agglutination, according to the White-Kauffmann-Le Minor scheme (Grimont and Weill, 2007), and their genomes were extracted and sequenced as previously described (Ung et al, 2019). Therefore, the total French dataset used for the source attribution and comparative genome studies comprised 440 genomes.…”

Antimicrobial Resistance and Biofilm Formation Capacity of Salmonella enterica Serovar Enteritidis Strains Isolated from Poultry and Humans in Poland

“…Host–host transmission in most Salmonella serovars usually occurs via the fecal–oral route, and the most common source of infection with Salmonella spp. is animal products, in particular those related to poultry, including poultry meat, eggs, and confectionery containing eggs [ 4 , 5 , 6 , 7 ]. Salmonellosis is often asymptomatic in poultry, and carrier status may occur, which might present a zoonotic threat.…”

Draft Genome Sequences of Salmonella enterica subsp. enterica Serovar Dublin Strains from St. Nectaire and Morbier Cheeses Characterized by Multilocus Variable-Number Tandem-Repeat Analysis Profiles Associated with Two Fatal Outbreaks in France

“…Human outbreaks of S. Dublin have been reported in many European countries and the United States (5–8). The outbreaks of S. Dublin reported in France in 2012 and in 2015 to 2016 due to St. Nectaire and Morbier cheese consumption, respectively, resulted in serious illness and a high mortality rate (5, 9).…”