Survie au froid et pathogénicité des souches de Yersinia enterocolitica BT4 isolées chez le porc et génétiquement proches ou non de souches isolées chez l'homme

En 2021, la yersiniose était toujours la troisième zoonose humaine la plus fréquemment identifiée en Europe (EFSA et ECDC, 2022). Les porcs sont décrits comme une source de Y. enterocolitica pathogènes pour l’homme. Une enquête française menée sur 2010-2011 en abattoir a montré que 13,7 % des porcs et que 74,3 % des lots de porcs étaient positifs en Y. enterocolitica pathogènes (Fondrevez et al., 2014). Au sein des 827 souches conservées lors de cette enquête, 91,9 % avaient le biotype BT4. Ce BT4 est le plus prévalent dans les cas de yersinioses humaines en France (66,8 %) (Le Guern et al., 2016). Pour que Y. enterocolitica puisse résister à la chaîne du froid et infecter l'homme, elle doit 1) survivre à la température de réfrigération, et 2) avoir les gènes pour exprimer sa pathogénicité. Le but de cette étude était de tester la survie au froid et la pathogénicité de quatre souches de Y. enterocolitica BT4 isolées de porcs et génétiquement proches ou non de souches isolées de cas humains.

Cold survival and pathogenicity of Yersinia enterocolitica BT4 strains isolated from pigs and genetically close or not to strains isolated from human cases

The aim of this study was to test the cold survival and pathogenicity of Yersinia enterocolitica BT4 strains isolated from pigs and genetically close or not to strains isolated from human cases, to assess their ability to pass through the food chain alive and infect humans. BT4 strains (n=50) of porcine origin (Anses and IFIP’s collections) and BT4 strains of human cases (n=50, CNR's collection) isolated in 2010 in France were sequenced. cgMLST, based on 1727 genes, was used to compare strains. Porcine strains and human strains in clusters were considered to be genetically closely related. Four porcine strains were selected: two closely related to human strains (P+H+), and two not (allelic difference > 9) (P+H-). The survival of these strains at 4°C was tested in BHI culture medium (5 Log10CFU/ml) and on ham (4.5 Log10CFU/cm2) for 10-11 days. Their pathogenicity was assessed using in vitro assays on human intestinal Caco-2 cells (105cells/ml of Caco-2 cells for 107 bacteria/ml). During the survival test at 4°C, an increase of 4 Log10CFU/ml in BHI and of 1.5-2.0 Log10 CFU/cm2on ham was observed for all strains. The P+H+ and P+H- strains did not differ significantly for the tests in BHI or on ham (P-value > 0.05). Adhesion and invasion on Caco-2 cells ranged from 65-90 % and 0.55-3.60 %, respectively. The P+H+ and P+H- strains did not differ significantly in pathogenicity. This study showed that the ability to survive and grow in cold conditions is not restricted to strains capable of infecting humans and that these strains had the same capacity to infect humans.