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Title: Genomic analysis and Next Generation Sequencing (NGS) of MDR plasmids in Salmonella enterica

item Frye, Jonathan

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/27/2011
Publication Date: 4/27/2011
Citation: Frye, J.G. 2011. Genomic analysis and Next Generation Sequencing (NGS) of MDR plasmids in Salmonella enterica. New Frontiers in Molecular Epidemiology II. April 26-28,2011. Decatur, GA.

Interpretive Summary:

Technical Abstract: Food animals harboring Multi-Drug Resistant (MDR) Salmonella enterica are a possible source of zoonotic human infections and are a potential risk to human health. MDR genes can be transmitted in a number of ways including via plasmids. MDR plasmid prevalence and distribution was investigated by studying a set of 437 Salmonella isolates obtained from clinically ill animals in 2005. Antimicrobial resistance (AR) phenotypes were determined, followed by a PCR assay for the presence of 18 plasmid replicon regions. A subset of 216 isolates was analyzed by PFGE. Cluster analysis based on the PFGE patterns showed that Salmonella positive for IncA/C plasmids grouped together based on serotype and MDR profile. This clustering determined that IncA/C plasmids and MDR has been associated with Salmonella previous to the introduction of the therapeutic use of antimicrobials and that the spread of resistance is likely due to the expansion of resistant clones rather than the accretion of new resistances. A subset of 59 isolates PCR positive for IncA/C plasmids were hybridized to a DNA microarray able to detect 775 AR genes and 493 IncA/C and H1 plasmid genes. This analysis further defined a core “backbone” of IncA/C plasmid genes and also identified variable regions associated with resistance to heavy metals that could explain the stability of MDR IncA/C plasmids in the absence of antimicrobial selective pressure. From these results, plasmid preparations from 32 isolates were sequenced by Next Generation Sequencing (Roche 454). Preliminary sequencing data confirmed the microarray data and identified and assembled contiguous sequences encoding IncA/C plasmid core genes as well as AR genes. Analysis of high-throughput DNA sequencing will enable the accurate determination of the history and evolution of IncA/C plasmids and the MDR genes they carry.