Abstract
Salmonella Infantis, a common contaminant of poultry products, is known to harbor mobile genetic elements that confer multi-drug resistance (MDR) and have been detected in many continents. Here, we report four MDR S. Infantis strains recovered from poultry house environments in Santa Cruz Island of the Galapagos showing extended-spectrum β-lactamase (ESBL) resistance and reduced fluoroquinolone susceptibility. Whole-genome sequencing (WGS) revealed the presence of the ESBL-conferring blaCTX-M-65 gene in an IncFIB-like plasmid in three S. Infantis isolates. Multi-locus sequence typing (MLST) and single nucleotide variant/polymorphism (SNP) SNVPhyl analysis showed that the S. Infantis isolates belong to sequence type ST32, likely share a common ancestor, and are closely related (1–3 SNP difference) to blaCTX-M-65-containing clinical and veterinary S. Infantis isolates from the United States and Latin America. Furthermore, phylogenetic analysis of SNPs following core-genome alignment (i.e., ParSNP) inferred close relatedness between the S. Infantis isolates from Galapagos and the United States. Prophage typing confirmed the close relationship among the Galapagos S. Infantis and was useful in distinguishing them from the United States isolates. This is the first report of MDR blaCTX-M-65-containing S. Infantis in the Galapagos Islands and highlights the need for increased monitoring and surveillance programs to determine prevalence, sources, and reservoirs of MDR pathogens.
Highlights
This article is an open access articleNon-typhoidal Salmonella (NTS) comprises multiple serovars of Salmonella enterica that can cause self-limiting or invasive enteric disease and are transmitted to humans mainly through contaminated food [1,2]
Most gastrointestinal infections caused by NTS are self-limiting; complicated infections can be treated by first-line antibiotics such as ampicillin, folic pathway inhibitors, and chloramphenicol
Antibiotic resistance is mediated by mutations in genes that are chromosomally encoded, or by genes carried by mobile genetic elements (MGE) such as plasmids, integrons, and transposons that are acquired from other bacteria in the environment through horizontal gene transfer [6]
Summary
This article is an open access articleNon-typhoidal Salmonella (NTS) comprises multiple serovars of Salmonella enterica that can cause self-limiting or invasive enteric disease and are transmitted to humans mainly through contaminated food [1,2]. The consumption of poultry products represents a common route of NTS transmission to humans [3], and the increasing prevalence of antimicrobial resistance (AMR) among NTS isolates has become a serious concern [4,5]. Most gastrointestinal infections caused by NTS are self-limiting; complicated infections can be treated by first-line antibiotics such as ampicillin, folic pathway inhibitors, and chloramphenicol. Strains of AMR NTS are globally disseminated, and their emergence has been linked to the overuse of antibiotics in agriculture and human medicine [7]. European countries have banned the sub-therapeutic use of antibiotics as growth promoters in commercially farmed animals [8], and some member states have since reported a reduction in the prevalence of AMR bacterial pathogens in food animals [9]. The practice continues in many developing, and some developed countries, serving as potential reservoirs from which MDR strains of NTS emerge as a result of a sustained selection pressure [9,10]
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