Prevalence and Antimicrobial Susceptibility Profile of Pseudomonas Aeruginosa Isolated from Diverse Clinical Specimens in A Tertiary Care Hospital

Abstract

Background: Pseudomonas aeruginosa is a ubiquitous, aerobic Gram-negative bacillus notorious for its capacity to colonise vulnerable patients and generate healthcare-associated infections that are notoriously difficult to manage. Its expanding multidrug-resistant (MDR) phenotype, underpinned by intrinsic low outer-membrane permeability, constitutive efflux pump expression, and a broad repertoire of acquired resistance mechanisms, has rendered empirical therapy increasingly unreliable and necessitates continuous local surveillance of susceptibility patterns.

Objectives: To isolate and confirm P. aeruginosa from diverse clinical specimens submitted to a tertiary care microbiology laboratory; to delineate the demographic and specimen-source profile of infected patients; and to generate a comprehensive, agent-specific antimicrobial susceptibility dataset against a representative panel of anti-pseudomonal antibiotics.

Methods: A prospective, descriptive, laboratory-based observational study was undertaken over six months (August 2025 to January 2026) at the Department of Microbiology, In a tertiary care hospital. A total of 174 non-duplicate P. aeruginosa clinical isolates were included. Species identification was performed by standard colonial morphology and a complete battery of biochemical tests (IMViC, oxidase, urease, TSI, OF test). Antimicrobial susceptibility testing was conducted by the Kirby-Bauer disk diffusion method on Mueller-Hinton agar in strict accordance with CLSI M100 guidelines (32nd edition, 2022).

Results: Male patients constituted 71.84% (n=125) of the study cohort. The >60-year age group yielded the highest number of isolates (32.76%). The majority of specimens originated from the in-patient department (83.33%). Sputum was the predominant specimen type (41.95%), followed by pus (17.24%) and ear swabs (15.52%). The General Medicine ward contributed the highest proportion of isolates (22.41%), followed by the ICU (18.97%). Among anti-pseudomonal agents tested, piperacillin-tazobactam demonstrated the highest sensitivity rate (87.93%), while the highest resistance rates were recorded for ceftazidime and aztreonam (42.53% each).

Conclusion: The study documents a concerning level of antimicrobial resistance in P. aeruginosa at this institution, particularly to third-generation cephalosporins and monobactams. Piperacillin-tazobactam and carbapenems retained relatively superior activity and may guide empirical treatment in clinically critical scenarios. Systematic susceptibility surveillance, stringent antimicrobial stewardship, and enhanced infection control measures are indispensable to curtail the dissemination of resistant clones.