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Title: Analysis of antimicrobial resistance genes detected in multiple-drug-resistant Escherichia coli isolates from broiler chicken carcasses

Author
item GLENN, LASHANDA - Former ARS Employee
item Englen, Mark
item Lindsey, Rebecca
item FRANK, JOSEPH - University Of Georgia
item TURPIN, JENNIFER - Former ARS Employee
item Berrang, Mark
item Meinersmann, Richard - Rick
item Cray, Paula
item Frye, Jonathan

Submitted to: Microbial Drug Resistance
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2012
Publication Date: 8/6/2012
Citation: Glenn, L.M., Englen, M.D., Lindsey, R.L., Frank, J.F., Turpin, J.E., Berrang, M.E., Meinersmann, R.J., Cray, P.J., Frye, J.G. 2012. Analysis of antimicrobial resistance genes detected in multiple-drug-resistant Escherichia coli isolates from broiler chicken carcasses. Microbial Drug Resistance. 18(4):453-463.

Interpretive Summary: Multi-drug resistant (MDR) bacteria are a potential problem in animal and human health. Antibiotics are required to treat some diseases, and antimicrobial resistance could result in treatment failure for some infections. To determine the genetic cause of resistance, 32 MDR Escherichia coli isolates from poultry were examined. Microarray analysis was used to detect hundreds of antimicrobial resistance genes and mobile genetic elements, such as plasmids, known to be associated with the spread of antimicrobial resistance genes among bacteria. Resistance genes were detected consistent with the MDR phenotypes of all isolates, and a large number of plasmid genes were detected in 27 isolates, indicating the likely presence of IncA/C plasmids, which are known to carry MDR genes. Testing for 18 plasmid types associated with MDR in Enterobacteriaceae detected one or more replicon type in all 32 isolates, and confirmed the presence of IncA/C in the 27 isolates. Class I integrons were also assayed for and detected in 25 of the isolates. The class I integrons detected ranged in size from ~1000 to 3300bp and sequence analysis identified antimicrobial resistance genes in these integrons. The genetic elements found in these isolates indicate that plasmids and integrons carrying antimicrobial resistance genes should be the focus of future studies to identify points where the spread of antimicrobial resistance genes in the poultry environment could be prevented by interventions.

Technical Abstract: Multi-drug resistant (MDR) bacteria in food animals are a potential problem in both animal and human health. In this study, MDR commensal Escherichia coli isolates from poultry were examined. Thirty-two E. coli isolates from broiler carcass rinses were selected based on resistance to aminoglycosides, ß-lactams, chloramphenicols, tetracyclines and sulfonamide antimicrobials. Microarray analysis for the presence of antimicrobial resistance and plasmid genes identified aminoglycoside (aac(6), aac(3), aadA, aph, strA and strB), ß-lactam (blaAmpC, blaTEM, blaCMY and blaPSE-1), chloramphenicol (cat, flo and cmlA), sulfamethoxazole (sulI and sulII), tetracycline (tet(A), tet(C), tet(D) and tetR) and trimethoprim (dfrA) resistance genes. A large number of IncHI1 plasmid genes (n=197) were detected in one isolate, while in 27 others a number of IncA/C genes were detected (mean=180) indicating the likely presence of these plasmids in the isolates. Eighteen plasmid replicon types often associated with MDR in Enterobacteriaceae were tested by polymerase chain reaction (PCR) and one or more replicon types were detected in all 32 isolates. Class I integrons were detected by PCR amplification of the integrase I (intI1) gene and insertion sizes were determined by amplification of the conserved flanking regions. Of the 25 isolates positive for the intI1 gene, class I integrons ranging in size from ~1000 to 3300bp were identified in 19 of them. The presence of class I integrons, IncA/C plasmid genes, and MDR associated plasmids in several isolates indicates the importance of these genetic elements in the accumulation and spread of antimicrobial resistance genes in the microbial community associated with poultry.