Oxacillin

The antibiotic susceptibility of P. konkukensis was determined according to the Kirby–Bauer disc diffusion method. The antibiotics used in this study were gentamycin (2 µg), vancomycin (30 µg), ampicillin (2 µg), tetracycline (30 µg), oxacillin (1 µg), kanamycin (64 µg), erythromycin (1 µg), chloramphenicol (30 µg), and clindamycin (2 µg) (Oxoid Ltd., Basingstoke, Hampshire, UK). The freshly prepared P. konkukensis bacterial culture incubated at 37 °C for 24 h was swabbed onto R2A agar plate using sterilized cotton swabs. Each disc of antibiotics was placed on the agar plate. After incubation at 37 °C for 48 h, a clear zone around the disc was observed.

The antimicrobial susceptibility profiles of the isolates were determined with disk diffusion method in accordance with the Clinical and Laboratory Standards Institute (CLSI) guidelines [24]. Antimicrobial agents that are generally used in veterinary hospitals in Korea were purchased from Oxoid and tested: penicillin (10 U), oxacillin (30 μg), cefazolin (30 μg), cefoxitin (30 μg), cefotaxime (30 μg), vancomycin (30 μg), gentamicin (10 μg), amikacin (30 μg), quinupristin-dalfopristin (15 μg), rifampin (5 μg), chloramphenicol (30 μg), trimethoprim-sulfamethoxazole (1.25/23.75 μg), ciprofloxacin (5 μg), minocycline (30 μg), tetracycline (30 μg), linezolid (30 μg), and erythromycin (15 μg). Shortly, an overnight culture of S. pseudintermedius was prepared in Muller–Hinton broth (Becton Dickinson) and was added to sodium chloride solution (0.45%; w/v) to achieve 0.5 McFarland standard turbidity. Then, the bacterial solution was inoculated by spread plating on Muller–Hinton agar using a sterile cotton swab. After allowing the inoculum to dry, the discs containing antimicrobials were placed onto the agar, and the cultures were incubated for 18–24 h at 37°C. A reference strain, Staphylococcus aureus (ATCC 25923), was used as control.