Pseudomonas aeruginosa is an opportunistic pathogen that usually does not cause infection in immunocompetent individuals, but can lead to severe disease in those with compromised immune systems. This organism is resistant to most antibiotic agents, and many clinical isolates of P. aeruginosa demonstrate multidrug resistance (MDR). In the present study, 150 clinical samples were obtained from various clinical sources in several hospitals located in Baghdad during the period of August through October of 2025. Identification of the isolates as P. aeruginosa was accomplished using morphological, microscopic, and biochemical assays, with confirmation of the isolate's identity via the VITEK2 system. Ultimately, there were 58 P. aeruginosa isolates successfully identified. The data from the current study indicate that burned patients had the greatest percentage of P. aeruginosa isolates (23; 39.66%), followed by infected wounds (16; 27.59%), ears (8; 13.79%), urine (7; 12.07%), and sputum (4; 6.90%). Antibiotic susceptibility testing performed on the P. aeruginosa isolates demonstrated that the greatest percent of isolates were resistant to the antibiotic agents piperacillin-tazobactam (86.2%), ceftazidime (75.9%), and ciprofloxacin (74.1%). Statistical evaluation revealed that ceftazidime-treated samples exhibited a significant decrease in gene expression for both pslA and pslD when compared to the control group (p ≤ 0.05); however, no statistically significant difference was observed between the ceftazidime-treated samples and the control samples for pqsA expression (p > 0.05)