A novel variant of Salmonella enterica serovar Typhimurium with a rough colony morphology and multidrug resistance

ABSTRACT: Salmonella enterica serovar Typhimurium (S. Typhimurium) is a major cause of salmonellosis, with various multidrug-resistant pathovariants emerging. Here, we investigated a distinct rough colony variant with potentially enhanced environmental adaptation in China. Whole-genome sequencing of 2,212 Chinese isolates and 1,739 publicly available isolates revealed the population structure and evolutionary history of the rough colony variants. These variants showed macro, red, dry, and rough (mrdar) colonies with better biofilm-forming abilities at 28 °C and 37 °C compared to typical rdar colonies. The mrdar variants displayed expansive multidrug resistance, mainly attributed to an IncHI2 plasmid carrying 19 antimicrobial resistance genes. Phylogenomic analysis divided global collections into six lineages, with the majority of mrdar variants in sublineage L6.5, which originated from Chinese smooth colony strains and possibly emerged circa 1977. Upregulation of the csgDEFG operons was observed among mrdar variants, probably due to a distinct point mutation (-44G>T) in the csgD gene promoter. Pangenome and genome-wide association analyses identified 87 specific accessory genes and 72 distinct single nucleotide polymorphisms associated with the mrdar morphotype. This study presents the first large-scale, genome-based study of a distinct rdar colony morphology variant of S. Typhimurium in China, highlighting its global epidemic potential. Ongoing surveillance and genomic epidemiological studies are required to control epidemics, monitor bacterial population changes, and assess associated risks to global public health.

ORGANISM(S): Salmonella Enterica Subsp. Enterica Serovar Typhimurium Str. Lt2

SUBMITTER: Juntao Yang  

PROVIDER: PXD047483 | iProX | Wed Mar 06 00:00:00 GMT 2024

REPOSITORIES: iProX