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 and plasmids from commensal Escherichia coli
Submitted to: American Society for Microbiology General Meeting
Publication Type: Abstract Only
Publication Acceptance Date: May 22, 2011
Publication Date: May 23, 2011
Citation: Lindsey, R.L., Frye, J.G., Thitaram, S.N., Cray, P.J., Englen, M.D. 2011. Analysis of antimicrobial resistance genes and plasmids from commensal Escherichia coli. American Society for Microbiology General Meeting. p. 121.
Background: Escherichia coli are commonly associated with various animal and environmental sources. They often acquire antimicrobial resistance (AR) to classes of drugs that are used to treat Gram-negative infections such as aminoglycosides, cephalosporins, fluoroquinolones and sulfonamides. Plasmids encoding antimicrobial resistance genes are a main factor in the transfer of resistance genes between bacterial strains and species. It is therefore important to identify and track the genetic elements responsible for resistance to better understand the mechanisms driving this problem. Methods: 35 E. coli isolates from 7 different food and companion animals were selected based on multi-drug resistant (MDR) resistance to clinically important antimicrobials. DNA was isolated from these isolates, fluorescently labeled, and hybridized to a microarray containing 489 MDR plasmid gene probes and 775 antimicrobial resistance genes. Results: Positive hybridizations were detected to both groups of gene probes including: aminoglycoside resistance (aac, aadA, aph, strA/B); Beta-lactam resistance (blaAMP, blaTEM, blaCMY); chloramphenicol resistance (cat, flo); sulfamethoxazole resistance (sul1); and tetracycline resistance (tet(A, C, D, R)). Eight isolates had core IncA/C plasmid genes detected, indicating they contained IncA/C plasmids. No individual gene probe was positive in all isolates. Conclusion: Overall our results showed similarities in the resistance genes detected in this diverse population of commensal E. coli. However, there was distinct genotypic variability. Additionally, all isolates hybridized to varied plasmid gene probes indicating the importance of these genetic elements in the accumulation and spread of antimicrobial resistance genes in of commensal E. coli from animal sources.