Antimicrobial Resistance and PFGE Molecular Typing of serovar Gallinarum Isolates from Chickens in South Korea from 2013 to 2018.

Antimicrobial resistance and pulsed-field gel electrophoresis (PFGE) genotypes of collected ser. Gallinarum isolates were investigated to examine the epidemiological relationship between field outbreak isolates of ser. Gallinarum. Thirty ser. Gallinarum isolates collected from poultry farms with FT outbreaks from 2013 to 2018 in South Korea were analyzed. All isolates were resistant to at least 3 of the 18 antimicrobials tested and exhibited an MDR phenotype. All isolates showed resistance to streptomycin, sulfisoxazole, and colistin. One isolate was resistant to 9 antimicrobials. The antimicrobial resistance profile, streptomycin-sulfisoxazole-colistin-nalidixic acid-ciprofloxacin-gentamicin (18/30, 60.0%), was the most prevalent. PFGE types were classified into 10 groups with a 100% correlation cutoff in dendrograms for 30 field isolates. The dominant PFGE types were 1 (8/30, 26.7%), 4 (7/30, 23.3%), and 9 (5/30, 16.7%). Interestingly some isolates collected from the same and different companies had the same PFGE type. We reported a high MDR rate in ser. Gallinarum isolates. The present study highlights the occurrence of horizontal spread and cyclic contamination of MDR ser. Gallinarum within the same company. Furthermore, we showed cross-contamination between different companies. The characterization of these isolates would be helpful in the development of prevention and control strategies for MDR ser. Gallinarum infection in South Korea.