Phylogenetic analyses of Salmonella detected along the broiler production chain in Trinidad and Tobago

Abstract

This study was conducted to determine the phylogenies of Salmonella strains isolated from cross-sectional studies conducted at hatcheries, broiler farms, processing plants, and retail outlets (broiler production chain) in Trinidad and Tobago over 4 yr (2016–2019). Whole-genome sequencing (WGS) was used to characterize Salmonella isolates. Core genome phylogenies of 8 serovars of public health significance were analyzed for similarities in origin and relatedness. In addition, Salmonella strains isolated from human salmonellosis cases in Trinidad were analyzed for their relatedness to the isolates detected along the broiler production chain. The common source of these isolates of diverse serovars within farms, within processing plants, between processing plants and retail outlets, and among farm-processing plant-retail outlet continuum was well-supported (bootstrap value >70%) by the core genome phylogenies for the respective serovars. Also, genome analyses revealed clustering of Salmonella serovars of regional (intra-Caribbean) and international (extra-Caribbean) origin. Similarly, strains of S. Enteritidis and S. Infantis isolated from human clinical salmonellosis in 2019 from Trinidad and Tobago clustered with our processing plant isolates recovered in 2018. This study is the first phylogenetic analysis of Salmonella isolates using WGS from the broiler industry in the Caribbean region. The use of WGS confirmed the genetic relatedness and transmission of Salmonella serovars contaminating chickens in broiler processing, and retailing in the country, with zoonotic and food safety implications for humans.