ARS | Publication request: Comparison of antimicrobial resistance determinants among Salmonella, Campylobacter, Escherichia coli, and Enterococcus isolated from Swine

Submitted to: International Association for Food Protection
Publication Type: Abstract Only
Publication Acceptance Date: May 30, 2008
Publication Date: August 2, 2008
Citation: Fry, P., Abley, M., Kaydos-Daniels, S., Cray, P.J., Gebreyes, W. 2008. Comparison of antimicrobial resistance determinants among Salmonella, Campylobacter, Escherichia coli, and Enterococcus isolated from Swine [abstract].International Association for Food Protection. P4-53. P. 145-146.

Technical Abstract: Introduction: The importance of Salmonella, Campylobacter, E.coli, and Enterococcus as carriers of antimicrobial resistance is well known, but limited work has been done to examine the relationship between this phenotypic characteristic and genotypic attributes among strains isolated in similar settings and time points. Purpose: The purpose of this project is to determine the role of peri-harvest factors on selection and dissemination of antimicrobial resistant foodborne and commensal organisms. Methods: Isolates were collected from processing plants in North Carolina and Iowa. Samples originated from the head meat, carcass, lairage swabs, and lymph nodes. Phenotypic characterization of antimicrobial resistance patterns was completed on 1,284 samples. Genotypic characterization by PCR and sequencing of resistance genes and class-1 integrons was performed on 128 isolates selected based on multidrug resistance pattern and association with other samples. Results: Phenotypically, all four pathogens were highly resistant to tetracycline, with the lowest prevalence being in Salmonella at 69.4%. Genotypically, the most common genes found are tetA(B) (26.6%), aadA2 (19.5%), and cmlA (18.0%). Within the samples that tested positive for tetA(B), aadE, and cmlA there were multiple groups of organisms that were from the same animal. Class-1 integrons were found in 43.75% of the samples with the majority found in Salmonella (22.7%) and Enterococcus (19.5%). Large (4kb) integrons were found in Salmonella serovar Havana and Enterococcus samples, unlike previous reports. Significance: The overlapping of resistance genes found within the four organisms may be the result of horizontal resistance gene transfer within the host. Large integrons among MDR Salmonella and enterococci is also of high significance since integrons facilitate the carriage and dissemination of multi-drug resistance.