COMPREHENSIVE PHENOTYPIC AND GENOTYPIC CHARACTERIZATION OF PSEUDOMONAS AERUGINOSA CLINICAL ISOLATES FROM A TERTIARY CARE HOSPITAL: INSIGHTS INTO VIRULENCE AND ANTIMICROBIAL RESISTANCE.

Background: Pseudomonas aeruginosa is a notorious Gram-negative opportunistic pathogen that plays a critical role in hospital-acquired infections (HAIs). It’s remarkable capacity to form biofilms and produce virulence factors, alongside mechanisms of antimicrobial resistance, complicates treatment strategies and worsens patient outcomes. Objectives: This study aimed to systematically investigate phenotypic traits and genetic determinants associated with virulence and resistance in P. aeruginosa isolates collected from diverse clinical specimens in a tertiary healthcare setting. Methods: Eighty non-duplicate P. aeruginosa isolates were recovered and confirmed using standard biochemical methods. Antibiotic susceptibility patterns were determined by Kirby-Bauer disc diffusion, following CLSI guidelines. Phenotypic assays for biofilm formation, hemolysin production, and elastase activity were performed. Molecular detection of virulence-associated genes (lasB, exoT, plcH, and pvdA) was conducted using PCR amplification followed by agarose gel electrophoresis. Results: Among the isolates, 62.5% originated from male patients, with pus samples accounting for 28.75% of all specimens. Imipenem exhibited the highest susceptibility (90%), whereas resistance was notably observed against ceftazidime and ciprofloxacin. Biofilm formation was present in 28.75%, hemolysin activity in 21.25%, and elastase production in 26.25% of isolates. Multidrug resistance was detected in 15% of isolates. Genotypically, pvdA was identified in 87.5%, exoT in 80%, lasB in 72.5%, and plcH in 66.25% of isolates. A significant correlation was established between phenotypic traits and gene presence (r = 0.54, p < 0.01), suggesting a direct relationship between virulence factors and antimicrobial resistance patterns. Conclusion: The coexistence of multiple virulence factors and antimicrobial resistance in P. aeruginosa underscores the need for integrated phenotypic and genotypic diagnostic approaches. These findings advocate for molecular surveillance programs and infection control interventions aimed at mitigating the spread and impact of resistant P. aeruginosa strains in healthcare settings.