Whole genome sequencing analyses revealed that Salmonella enterica serovar Dublin strains from Brazil belonged to two predominant clades

Abstract

Salmonella Dublin is a cattle-associated serovar sporadically causing disease in humans. S. Dublin strains isolated in Brazil and in other countries were analyzed to determine their phylogenetic relationships, the presence of genes, plasmids, genomic regions related to virulence and antimicrobial resistance genes repertoire, using WGS analyses. Illumina was used to sequence the genome of 112 S. Dublin strains isolated in Brazil from humans (n = 82) and animals (n = 30) between 1983 and 2016. Furthermore, 87 strains from other countries were analyzed. WGSNP analysis revealed three different clades, in which the strains from Brazil belonged to two clades, A and C. Most of the genes and genomic regions searched varied among the strains studied. The siderophore genes iroB and iroC were exclusively found in strains from Brazil and pegD gene, related to fimbrial adherence determinants, were positive in 124 strains from clades A and B but absent in all the strains from clade C (n = 71). Eleven plasmid replicons were found in the strains from Brazil, and nine were exclusively found in strains from other countries. The antimicrobial resistance genes mdsA and mdsB, that encode an efflux pump, were found in all the strains studied. The strains from Brazil carried other resistance genes, such as tet(A) (n = 11), tet(B) (n = 4) and tet(C) (n = 4), blaTEM-1 (n = 4), catA1 (n = 1), aadA1 (n = 1), and sul1 (n = 1). In conclusion, S. Dublin strains isolated in Brazil presented some few unique genes not found in strains from other countries and were allocated into two distinct clades with strains of human and animal origin epidemiologically related. This fact stresses the zoonotic potential of S. Dublin circulating in Brazil for more than 30 years.