Antimicrobial Susceptibility of Human Pasteurella multocida Isolates in Korea, 2022–2025

BACKGROUND: is an important zoonotic pathogen that causes soft-tissue infections in humans; however, recent antimicrobial susceptibility data in Korea remain limited. MATERIALS AND METHODS: isolates collected at a nationwide commercial laboratory in Korea between November 2022 and July 2025 were analyzed. Antimicrobial susceptibility testing was performed using the disk diffusion method on Mueller-Hinton agar supplemented with 5% sheep blood. Five clinically relevant antimicrobial agents were tested: penicillin, amoxicillin-clavulanic acid (AMC), levofloxacin, tetracycline, and trimethoprim-sulfamethoxazole (TMP-SMX). For isolates classified as penicillin non-susceptible by disk diffusion, minimum inhibitory concentration (MIC) testing was performed using E-test and β-lactamase production was assessed using a phenotypic method. RESULTS: All tested isolates were susceptible to tetracycline and TMP-SMX by disk diffusion. Susceptibility rates by disk diffusion were 97.1% for AMC, 91.4% for levofloxacin, and 85.7% for penicillin. All 10 isolates initially classified as penicillin non-susceptible by disk diffusion were confirmed to be susceptible to penicillin by MIC testing and were β-lactamase negative. The 2 isolates classified as non-susceptible to AMC by disk diffusion were also β-lactamase negative and susceptible to penicillin by MIC testing. CONCLUSION: isolates in Korea.