MIC Distributions and CLSI-Categorized Resistance in Pseudomonas aeruginosa from Companion Animals in Poland: Evidence of Strong Meropenem–Ceftazidime Co-Non-Susceptibility

<i>Pseudomonas aeruginosa</i> is a clinically important opportunistic pathogen in dogs and cats, frequently associated with chronic infections and increasing antimicrobial resistance. In 2024, 111 <i>P. aeruginosa</i> isolates from 77 dogs and 34 cats were analyzed. Isolates originated from the external ear canal of animals with chronic otitis externa (66/111, 59.5%) and the nasal cavity of animals with chronic rhinitis (29/111, 26.1%), wounds (7/111, 6.3%), the conjunctival sac (5/111, 4.5%), and the skin (4/111, 3.6%). MICs for ciprofloxacin, meropenem, ceftazidime, aztreonam, piperacillin, piperacillin/tazobactam, and colistin were determined using a commercial microdilution panel and interpreted with CLSI M100 breakpoints for <i>P. aeruginosa</i>. Susceptibility was highest to piperacillin and piperacillin/tazobactam (both 90.1% susceptible and 7.2% resistant). Resistance was more frequent to ciprofloxacin (26.1%), meropenem (17.1%), and ceftazidime (16.2%). Colistin resistance (MIC ≥ 4 µg/mL) was detected in 6.3% of isolates. MDR (Magiorakos definition; non-susceptibility to ≥1 agent in ≥3 antimicrobial categories) was identified in 17/111 (15.3%) isolates. Meropenem non-susceptibility was strongly associated with ceftazidime non-susceptibility (25/111, 22.5%; OR 11.21; 95% CI 4.29-29.30; phi 0.51; <i>p</i> = 2.4 × 10^-7). These findings provide baseline phenotypic surveillance data for <i>P. aeruginosa</i> from companion animals in Poland and highlight clinically relevant co-non-susceptibility patterns involving meropenem and ceftazidime.