EPIDEMIOLOGY, ECOLOGY, AND MOLECULAR GENETICS OF ANTIMICROBIAL RESISTANCE IN PATHOGENIC AND COMMENSAL BACTERIA FROM FOOD ANIMALS
Location: Bacterial Epidemiology and Antimicrobial Resistance
Title: Analysis of Antimicrobial Resistance Genes in Multiple Drug Resistant (MDR) Escherichia coli Isolated from Broiler Chicken Carcasses
Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: April 2, 2010
Publication Date: May 25, 2010
Citation: Glenn, L.M., Lindsey, R.L., Cray, P.J., Frye, J.G. 2010. Analysis of Antimicrobial Resistance Genes in Multiple Drug Resistant (MDR) Escherichia coli Isolated from Broiler Chicken Carcasses. American Society for Microbiology. May 23 - 27, 2010. San Diego, CA. Poster#A-1012.
Background: MDR food-borne bacteria are a concern in both animal and human health. To understand the mechanisms driving this problem, the genetic elements responsible for resistance need to be determined and analyzed. Methods: From 2000-2007, 16,912 Escherichia coli were isolated from broiler carcass rinses and subjected to antimicrobial susceptibility testing via SensititerTM (TREK Diagnostics, Inc, Westlake, OH). DNA was isolated from a representative subset of MDR isolates (n=32), fluorescently labeled, and hybridized to a microarray containing 775 antimicrobial resistance genes and 489 MDR plasmid gene probes. The presence of class I integrons was determined using PCR of integrase I (IntI) and the size of the integrons was determined by PCR of the conserved flanking regions. Plasmid replicon typing by multiplex PCR was used to determine the presence/absence of 18 plasmids often associated with MDR in Enterobacteriaceae. Results: Gene probes with positive hybridizations included: aminoglycoside resistance (aac, aadA, aph, strA and strB); beta-lactam resistance (blaAMP, blaTEM, blaCMY-2, blaCMY-13, blaOXA and blaSHV); chloramphenicol resistance (cat, flo and cmlA); sulfamethoxazole resistance (sul1, sulI and sulII); tetracycline resistance (tet(A), tet(C), tet(D) and tet(R)); and trimethoprim resistance (dfrA, dhrf and dhf). Twenty-five isolates were positive for IntI gene, class I integrons were amplified in 19 isolates and ranged in size from 1000 to 3300bp. One isolate contained a large number of H1 plasmid genes (n=197) while 28 isolates contained many IncA/C plasmid genes (average=171). One or more plasmids were detected in 29 isolates using multiplex PCR. Conclusions: Overall, there was a positive correlation between the antimicrobial susceptibility and resistance genes detected via microarray. Similar resistance genes were found among the isolates regardless of year of isolation. The presence of variable sized class I integrons, IncA/C plasmid genes, and MDR associated plasmids may indicate the importance of these genetic elements in the accumulation and/or spread of antimicrobial resistance genes in the poultry microbial community.