Molecular Characterization of Multi-Drug-Resistant Clinical Isolates of Pseudomonas aeruginosa in Osun State, Nigeria

Background: Pseudomonas aeruginosa is an opportunistic pathogen of humans and is associated with high rates of morbidity and mortality in hospital-acquired infections. This study aimed to elucidate the molecular mechanisms of antibiotic resistance and virulence in multidrug-resistant (MDR) P. aeruginosa isolated from clinical samples in Osun State, Nigeria. Methods: One hundred and twenty (120) clinical isolates of P. aeruginosa were randomly collected from the Medical Microbiology Laboratory of Osun State University Teaching Hospital, Osogbo, between January 2018 and November 2019. The isolates were cultured on cetrimide agar plates and identified based on colonial morphology and biochemical character-istics. Antibiotic susceptibility testing was performed using the Kirby-Bauer disc diffusion method, and antibiotic resistance genes were detected using polymerase chain reaction (PCR). Results: All the isolates were resistant to ampicillin, amoxicillin–clavulanate, cefotaxime, cefpodoxime, cefepime, and ticarcillin, while 91.7% (n = 110) and 90.8% (n = 109) were resistant to tetracycline and ceftazidime, respectively. They were all sensitive to meropenem; however, low rates of resistance were observed for imipenem (8/6.7%), gentamicin (20/16.7%), amikacin (23/19.2%), polymyxin B (28/23.3%), and ciprofloxacin (49/40.8%). The blaCTX-M-15 (100/83.3%), blaTEM-1 (96/80.0%), blaSHV-1 (90/75.0%), blaKPC (8/6.7%), and blaNDM (8/6.7%) resistance genes were seen in the isolates. The isolates produced lasB (73/60.8%), ExoS (72/60.0%), rhlAB (70/58.3%), algD (64/53.3%), toxA (55/45.8%), and pilB (20/16.7%) virulence genes. Conclusion: Multidrug-resistant P. aeruginosa is a major public health concern; the identification of its resistance and virulence genes provides important insights into the pathogen’s adaptability and its impact on patient outcomes and infection control.