Intercontinental spread and clonal expansion of ColRNA1 plasmid-bearing Salmonella Corvallis ST1541 strains: a genomic epidemiological study.

Salmonella Corvallis ST1541 has recently emerged as a globally disseminated pathogenic strain that often causes severe food-borne infections. Unlike most pandemic serotypes of Salmonella, the ST1541 strains harbored ColRNA1 plasmids that contain qnr-like determinants known to be responsible for the increasing incidence of ciprofloxacin-resistant food-borne Salmonella infections. In this study, we conducted a genomic analysis of a global collection of 388 S. Corvallis ST1541 strains collected within a twenty-year period. We investigated the genetic characteristics of plasmid-mediated quinolone resistance (PMQR) plasmids harbored by these S. Corvallis strains, established a minimum spanning tree (MST) to determine the temporal and spatial distribution of the top 10 MST clusters, inferred a time-phylogenies for the major sub-lineages and traced the routes of international dissemination of this serotype strains. Bayesian algorithm predicted that UK might be the origin of S. Corvallis strains currently prevalent in various countries. This idea is supported by the observation of the emergence of intercontinental-disseminated clonal strains and extensive transmission of the extensive-drug resistance (XDR)-encoding plasmid pSA663. This study therefore provides valuable insight into the evolution of globally transmitted S. Corvallis strains and suggests a need to strengthen cooperation between different countries to control the dissemination of these drug-resistant bacteria. [ABSTRACT FROM AUTHOR]