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 detected in Campylobacter coli, Enterococcus spp., Escherichia coli and Salmonella enterica isolated from the same animal sample
Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: May 17, 2009
Publication Date: May 17, 2009
Citation: Frye, J.G., Jackson, C.R., Englen, M.D., Meinersmann, R.J., Berrang, M.E., Cray, P.J. 2009. Analysis of antimicrobial resistance genes detected in Campylobacter coli, Enterococcus spp., Escherichia coli and Salmonella enterica isolated from the same animal sample [abstract]. American Society for Microbiology. May 17 - 21, 2009. Philadelphia, PA. A-051.
Background: The potential spread of antimicrobial resistant bacteria through the food chain is concerning. Animals may provide an environment for the exchange of antimicrobial resistance (AR) genes among bacteria; therefore a study was developed to identify AR genes found in common among commensal and pathogenic bacteria in swine. Methods: Campylobacter coli, Enterococcus spp., Escherichia coli and Salmonella enterica were co-cultured from fecal samples collected on-farm from swine. All four bacteria were isolated from 49 fecal samples for a total of 194 isolates, 49 of each genus. These isolates were further analyzed for AR phenotype and genotype. Phenotypic testing was done by automated broth micro-dilution with a panel of antimicrobials (Sensititer, TREK Diagnostic Systems, Inc., Westlake, OH, USA). AR genes were analyzed with a DNA microarray containing probes for 775 resistance genes. DNA extractions, labeling, hybridization, image and data analysis were done following standard microarray techniques (Corning Inc., Acton, MA, USA). Results: 417 different antimicrobial resistance genes and mobile element probes had positive hybridizations with one or more of the isolates. An average of 30 and 33 genes were detected in Salmonella and E. coli isolates respectively. C. coli averaged four genes and Enterococcus spp. averaged nine genes detected. Approximately half of Salmonella and E. coli isolated from the same fecal sample had common genes detected including ones encoding resistance to aminoglycosides (aadA, aadB, and aph(3)-I), beta-lactams (blaAMPC and blaTEM), sulfanilamide (sulI), tetracycline (tetA, tetB, and tetR) and mobile elements (intI, tnpA, and tnpR). However, very few common AR genes were found between Salmonella and E. coli and the other isolates. All C. coli and Enterococcus spp. isolates had fewer genes detected, however nine pairs did share genes including tet(O) and aph(3). Conclusions: These data demonstrate that common AR genes were found in different species of bacteria isolated from the same fecal sample. This may be evidence for transfer or a common source of AR genes among bacteria in these animals.