Antimicrobial Resistance of Salmonella enterica from Chickens in South Korea

Introduction: Salmonella enterica (S. enterica) infections by poultry products has been a major food-borne illness even though only several serotypes cause most human infections. For control, antimicrobial drugs have been widely used and the emergence of multidrug resistance especially to fluoroquinolones and third-generation cephalosporins associated with poultry is also an increasing threat to public health in South Korea.

Purpose: In the present study, we examined antimicrobial resistance of recent isolates of S. enterica from chickens and environments for the control of Salmonella infection in chicken.

Methods: S. enterica isolates (n=104) from chickens and environments of chicken farms and slaughter houses in South Korea in 2015 were serotyped and tested for an antimicrobial susceptibility by determining minimum inhibitory concentrations(MICs) to 15 antimicrobials using customized panels (Sensititre; Trek Diagnostics, Westlake, OH, USA).  

Results: Thirteen serovars of S. enterica were identified in the isolates except 2 unidentified isolates. A total of 104 isolates of S. enterica from chickens and environments showed 32 different antimicrobial resistance pattern, respectively. Most isolates of S. enterica (94 /104; 90.4%) were resistant to nalidixic acid and 61.5% (64/104) of the isolates showed resistance to at least five antimicrobials. Moreover, the resistance rate to third-generation cephalosporin (ceftiofur) and fluoroquinolone was 17.3% (18/104) and 2.9% (3/104) in S. enterica isolate, respectively

Significance: These data showed high frequency of multi-drug resistance (MDR) and also resistance to fluoroquinolones and third-generation cephalosporins in S. enterica isolates from chickens and environments in South Korea. Appropriate intervention strategies is needed for control of Salmonella infections and reducing antimicrobial resistance in chickens.