Antimicrobial Resistance Profiles of <i>Pseudomonas aeruginosa</i> in a Korean Community Hospital: <i>In Vitro</i> Activity of Ceftazidime-Avibactam and Other Agents

The novel antibiotic ceftazidime-avibactam was introduced in Korea in 2023. This study evaluated the <i>in vitro</i> susceptibility of <i>Pseudomonas aeruginosa</i> isolates from a community-based hospital to various antibiotics, including ceftazidime-avibactam. A total of 100 non-duplicated consecutive <i>P. aeruginosa</i> isolates obtained from clinical specimens collected between October 2017 and March 2018 were analyzed. The minimum inhibitory concentrations (MICs) for ceftazidime, ceftazidime-avibactam, and colistin were determined by broth microdilution. Susceptibility to other antibiotics was assessed using the MicroScan system. Carbapenemase genes were detected by multiplex PCR. Among 100 isolates, 37% were multidrug-resistant (MDR), 27% were carbapenem-resistant (CR), and 9% were difficult-to-treat (DTR) <i>P. aeruginosa</i>. Colistin exhibited the highest efficacy against MDR and CR <i>P. aeruginosa</i> (MIC_50/90=1/4 mg/l, 89.2% and 88.9% susceptible), followed by ceftazidime-avibactam (MIC_50/90=4/16 mg/l, 86.5% and 85.2% susceptible). For DTR isolates, colistin (MIC_50/90=1/8 mg/l, 77.8% susceptible) was the most effective, followed by ceftazidime-avibactam (MIC_50/90= 4/≥128 mg/l, 66.7% susceptible). Carbapenemase genes were identified in four of 27 CR isolates (14.8%), including IMP- and KPC-type enzymes. Appropriate antibiotic use was observed in 71.4% of the non-MDR group and 56.8% of the MDR group. Clinical success was higher in the non-MDR group (85.7% vs. 64.9%, <i>p</i>=0.029), and <i>P. aeruginosa</i> infection was more frequently the cause of death in the MDR group (27% vs. 9.5%, <i>p</i>=0.043). <i>P. aeruginosa</i> isolated from a community-based hospital showed high antibiotic resistance, posing treatment challenges. Ceftazidime-avibactam may be a viable treatment option for MDR <i>P. aeruginosa</i> infections and warrants further clinical evaluation in Korea.