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Title: Antimicrobial susceptibility and plasmid replicon typing of Salmonella enterica serovar Kentucky isolates recovered from broilers

Author
item LADELY, SCOTT R. - Food Safety Inspection Service (FSIS)
item Ball, Takiyah
item Meinersmann, Richard - Rick
item FEDORKA-CRAY, PAULA J - Former ARS Employee

Submitted to: American Meat Science Association Conference Reciprocal Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 6/9/2015
Publication Date: 6/14/2015
Citation: Ladely, S., Ball, T.A., Meinersmann, R.J., Fedorka-Cray, P. 2015. Antimicrobial Susceptibility and Plasmid Replicon Typing of Salmonella enterica serovar Kentucky isolates recovered from Broilers. 68th American Meat Science Association Conference Reciprocal Proceedings. June 14-17, 2015. Lincoln, Nebraska.

Interpretive Summary:

Technical Abstract: In the United States, Salmonella enterica serotype Kentucky has become the predominate serotype recovered from broiler slaughter samples and the prevalence of resistance to streptomycin and tetracycline has increased dramatically in this serotype. To characterize the relationships between antimicrobial resistance, genotype, and plasmid replicon types among S. Kentucky derived from poultry, 600 isolates representing a ten year period (2004 – 2013) were randomly chosen from the animal arm of the National Antimicrobial Resistance Monitoring System Salmonella collection, susceptibility to 15 antimicrobials, pulsed-field gel electrophoresis, and plasmid incompatibility (Inc) replicon types were determined, and linkage disequilibrium analysis was performed. Antimicrobial resistance was most common for tetracycline (50.0%) and streptomycin (46.5%). Resistance to ampicillin, amoxicillin-clavulanic acid, ceftriaxone, ceftiofur and cefoxitin ranged from 14.3% to 16.7%. The most prevalent Inc replicon types observed were I1 (62.0%), FIB (47.3%) and HI2 (8.7%). Replicon types A/C, K/B, P, and FIC were detected in less than 1% of the isolates. IncI1, HI2, and A/C were significantly linked to 8, 7, and 9 antimicrobials, respectively and FIB was linked with streptomycin and tetracycline resistance only. Cluster analysis based on PFGE revealed 112 unique types sharing 73.0% similarity. Analysis also revealed two large clusters consisting of 144 and 190 isolates. The larger of the two clusters had significantly (p<0.05) more isolates resistant to streptomycin (68.9%) and tetracycline (92.1%) compared the smaller cluster (11.8% and 13.2% for streptomycin and tetracycline, respectively) or the remainder of the isolates examined (n=266, 49.2% and 39.8% for streptomycin and tetracycline, respectively). We conclude the dramatic increase in streptomycin and tetracycline resistance among S. Kentucky derived from poultry is the result of clonal expansion of a strain harboring plasmid replicon type FIB.