Genome divergence and increased virulence of outbreak associated Salmonella enterica subspecies enterica serovar Heidelberg

In this study, we compared the genomes of outbreak associated non-outbreak causingSalmonella ser.Heidelberg strains from diverse hosts and geographical regions. Human outbreak associated strains in this study were from a 2015 multistate outbreak ofSalmonella ser.Heidelberg involving 15 states in the United States which originated from bull calves. Our clinicopathologic examination revealed that cases involvingSalmonella ser.Heidelberg strains were predominantly young, less than weeks-old, dairy calves. Pre-existing or concurrent disease was found in the majority of the calves. Detection ofSalmonella ser.Heidelberg correlated with markedly increased death losses clinically comparable to those seen in herds infected withS. Dublin, a known serious pathogen of cattle. Whole genome based single nucleotide polymorphism based analysis revealed that these calf isolates formed a distinct cluster along with outbreak associated human isolates. The defining feature of the outbreak associated strains, when compared to older isolates ofS.Heidelberg, is that all isolates in this cluster containedSaf fimbrial genes which are generally absent inS.Heidelberg. The acquisition of several single nucleotide polymorphisms and the gain ofSaf fimbrial genes may have contributed to the increased disease severity of theseSalmonella ser.Heidelberg strains.
Source: Gut Pathogens - Category: Microbiology Source Type: research