Identification and molecular characterization of class 1 integrons in multiresistant Escherichia coli isolates from poultry litter

Abstract

This study describes the prevalence of arrays of class 1 integron cassettes and Qnrdeterminants (A, B, and S) in 19 fluoroquino lone- resistant Escherichia coli isolates from chicken litter. qnrS and qnrA were the predominant genes in these fluoroquinoloneres istant isolates, and an uncommon array of aacA4-catB3-dfrA1 gene cassettes from a class1integron was found. Additionally, aadA1 and dfrA1 gene cassettes, encoding resistance tostreptomycin and trimethoprim, constituted the mostcommon genes identified and was located on megaplasmids as well on the chromosome. Antibiotic resistance, pulsed-field gel electrophoresis (PFGE), and plasmid data suggest a genetically diverse origin of poultry E. coli isolates. © 2012, American Society for Microbiology.