An oligonucleotide microarray to characterize multidrug resistant plasmids

Many of the Enterobacteriaceae carry multiple drug resistance (MDR) genes on large plasmids of replicon type Inc A/C and Inc H1. It is important to understand the transmission of these MDR plasmids because the genes they carry can affect the outcome of antimicrobial therapy. The aim of this study was to design a microarray with oligonucleotide probes for every gene in the six Inc A/C and one Inc H1 plasmids of interest while representing all redundant sequences only once. The microarray is printed in triplicate with 493 unique oligonucleotide probes 70 nucleotides in length. Salmonella enterica and Escherichia coli control strains and test plasmids (in the parent strain and transformed into a known E. coli background strain) were hybridized to the plasmid microarray. This hybridization arrays presents a rapid and cost effective method for high-density screening of isolates to evaluate the gene content of Inc A/C and H1 plasmids and will show how plasmids can change content with transmission.