Source-attribution study of S. Derby sporadic cases in France (En préparation)

Suite à la production des génomes de référence pour S. Derby, il a été possible de construire une phylogénie plus fine à partir d’une référence adaptée à la lignée majoritaire (ST40). Nous avons inclus l’ensemble des 302 souches humaines collectées en France en 2014-2015 afin de déterminer la source-attribution des souches humaines. Nos résultats montrent la présence, chez l’humain, des 4 lignées identifiées (ST39, ST40, ST71, ST682) dans les aliments. Cependant les lignées identifiées chez le porc (les ST40, ST39 et ST682) représentent 93% des cas humains, là où les souches issues du ST71 n’en représentent que 2% (6/302). 13 profils sporadiques propres aux souches humaines sont également identifés correspondant essentiellement à des profils ST encore non définis. limiting gastroenteritis with 550 million people getting sick each year, including 220 children under 5 year old. Salmonella is one of the 4 main causes of gastroenteritis (WHO, 2018). Salmonellosis is usually characterized by acute onset of fever, abdominal pain, diarrhea, nausea and sometimes vomiting. The onset of disease symptoms occurs 6–72 hours (usually  12–36 hours) after ingestion of Salmonella, and illness lasts 2–7 days (WHO, 2018). Symptoms of salmonellosis are relatively mild and patients will make a recovery without specific treatment in most cases. However, in some cases, particularly in children and elderly patients, the associated dehydration can become severe and life-threatening. Salmonella enterica subsp. enterica serotype Derby (S. Derby) is one of the serovars whose food poisoning mainly affects the population at risk (elderly or children). Appart from these cases, most of the S. Derby cases are considered sporadic. In 1946, S. Derby caused an epidemic in Australia in 68 infants and young children causing the death of 10 of them (Mushin, 1948). In 1963, an outbreak caused by egg contamination by S. Derby caused 822 cases in 53 hospitals in the United States (Sanders et al., 1963). More recently, between the end of 2013 and the beginning of 2014, S. Derby is responsible for an outbreak in Germany involving 145 patients, mostly elderly people in Berlin and the Brandenburg region in Germany (Simon et al., 2017). In China, S. Derby is the third most reported serovar in clinical cases (Ran et al., 2011) and the most reported serovar in infants and toddlers (Cui et al., 2009). Otherwise these outbreaks affecting immune depressed people, this serovar is mainly associated with sporadic cases: in the United States, from 2005, S. Derby causes an average of 120 cases each year (CDC, 2017). In Europe S. Derby is the 5th most isolated serovar in human with 570 cases in 2016 (EFSA, 2017). In France, S. Derby varied between the 8th to the 5th position (n =164 to 178 clinical isolates) of the most frequently isolated serotypes in humans since 2000 (Weill, 2014).

The principal reservoirs of this pathogen are pigs and poultry worldwide. S. Derby was recorded as the most abundant serovar isolated from slaughter pigs with a presence in 28.5% of the production holding in whole European Union in 2008 (European Food Safety, 2008). It This serovar adapted to pigs and poultry animals is frequently isolated from pork meat. Several studies have associated pork meat and S. Derby (Valdezate et al., 2005; Hauser et al., 2011; Kerouanton et al., 2013; Simon et al., 2017; Zheng et al., 2017). In Europe, S. Derby accounted for 22.9% of the isolates from pork meat, followed by monophasic strains of S. Typhimurium (22.3%) and S. Typhimurium (20.6%) (EFSA, 2016). Data from the ANSES Salmonella Network (jointly with the National Reference Laboratory) show that this serovar is mainly isolated from This serovar adapted to pigs and poultry animals is frequently isolated from pork meat. Several studies have associated pork meat and S. Derby (Valdezate et al., 2005; Hauser et al., 2011; Kerouanton et al., 2013; Simon et al., 2017; Zheng et al., 2017). In Europe, S. Derby accounted for 22.9% of the isolates from pork meat, followed by monophasic strains of S. Typhimurium (22.3%) and S. Typhimurium (20.6%) (EFSA, 2016). Data from the ANSES Salmonella Network (jointly with the National Reference Laboratory) show that this serovar is mainly isolated from pork and poultry meat in France with 242/598 (40%) and 63/598 (11%) isolates respectively between 2014 and 2015 (Leclerc et al., 2016).