Salmonella Muenchen ST82 in poultry and humans

Foodborne salmonellosis poses a major threat to public health globally. Since 2018, Salmonella Muenchen has emerged in Israel in both human and poultry. However, little is known about the role of poultry in the surge of human cases, and the transmission pathways within the broiler industry, which is crucial for setting effective control measures to prevent its spread and protect public health. Whole genome sequencing was utilized to compare between: i) isolates (n=99) from broiler production sector, layers, food sources and human clinical cases collected in Israel between June 2020 and January 2022; ii) isolates (n=70) collected from the broiler industry to represent potential transmission pathways between different growth stages and within farms; and (iii) emerging strains in Israel with a selection (n=125) of publicly available S. Muenchen sequences. High genetic similarity was found between human and poultry isolates. Strains were exclusively ST82, exhibited multi drug resistance (MDR), including high rates (58.6%) of quinolone resistance determinants, and harboured the pESI plasmid. S. Muenchen is prevalent in 61.5% (CI95%=51.5-71.5%) of broiler flocks, and strains were unable to be traced back to breeder flocks, however on-farm transmission and persistence in barns were evident. The Israeli S. Muenchen isolates were genetically similar to pESI-positive isolates from USA, UK and South Africa. The clonal spread of pESI-positive MDR S. Muenchen ST82 in the poultry industry is contributing to an increased incidence in humans in Israel. Horizontal transmission within the broiler industry requires adaptation of control measures to protect public health.