Identification of Antimicrobial Resistance Genes and Plasmid Types in Isolates of Salmonella Enterica

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Medicine and Health Sciences


Multiple drug resistance is becoming increasingly problematic in the U.S., where antibiotics are overused both in agriculture and healthcare. One way bacteria can develop this resistance is through acquisition of antibiotic resistance genes either on their chromosomes or on plasmids. A plasmid is an autonomous extrachromosomal DNA structure that replicates independently of the bacterial chromosome. Plasmids can be horizontally spread across different bacterial species through conjugation, allowing multiple bacteria the ability to select for a resistant, advantageous phenotype. Typing and characterization of plasmids is important in order to better understand and trace the spread of this resistance. Salmonella enterica, one of the major causes of intestinal illnesses worldwide, has acquired resistance to a number of different antibiotics. The objective of this study was to confirm the presence and location of antimicrobial resistance genes and identify plasmid types in clinical isolates of Salmonella. This was achieved by analyzing their sequenced genomes using web-based programs put together by Center for Genomic Epidemiology . Three programs, PlasmidFinder, ResFinder, and Plasmid Multi locus Sequence Typing (pMLST) were used to provide better characterization and typing of S. enterica plasmids and the resistance genes carried on these plasmids. With the help of these three programs the number of plasmids in five different Salmonella enterica clinical isolates were confirmed, the plasmids were divided into different incompatibility groups, and the resistance genes carried by these plasmids were identified. This analysis will be beneficial in comparing the newly identified plasmids to other plasmids belonging to certain incompatibility groups that have been well studied and found to be associated with specific resistance genes. This will greatly aid in assigning these plasmids to lineages that can in turn help with future comparative analysis studies in order to better understand and combat the spread of resistance in Salmonella.


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