Phenotypic Characterization of Multidrug-Resistant Pseudomonas aeruginosa Isolated From Patients With Ventilator-Associated Pneumonia: Insights Into Resistance Mechanisms and Biofilm Formation

BackgroundIn patients receiving mechanical ventilation in intensive care units (ICUs), ventilator-associated pneumonia (VAP) is a serious illness connected with healthcare.Pseudomonas aeruginosa (P.aeruginosa) is among the most often used pathogens linked to VAP and is increasingly characterized by multidrug resistance, βlactamase production, and biofilm-forming ability.This study focused on assessing the antimicrobial susceptibility pattern, prevalence of multidrug resistance, extended-spectrum β-lactamase (ESBL) production, metallo-β-lactamase (MBL) production, and biofilm-forming ability among isolates of P. aeruginosa collected from endotracheal tube (ETT) aspirates of individuals with VAP. MethodsA descriptive cross-sectional research study was carried out in the Microbiology Department at Krishna Charitable Hospital and Medical Research Center, Karad, India.A total of 104 non-repetitive P. aeruginosa isolates acquired from ETT aspirates of patients clinically suspected of VAP were included.Identification was carried out utilising conventional microbiological and biochemical methods.Antimicrobial susceptibility testing was performed using the Kirby-Bauer disk diffusion method.ESBL and the production of MBLs were detected phenotypically by combined disk diffusion methods.The Congo red agar (CRA) method and the Christensen's tube method were used to evaluate biofilm development. ResultsAmong the 104 VAP patients, 72 (69.23%) were male, and 32 (30.77%) were female.The highest proportion of cases was observed in the 21-40-year age group (45.65%).Most (49.04%) of VAP cases occurred in the medical intensive care unit (MICU), and 54.81% of cases appeared five days after starting mechanical ventilation.Antimicrobial susceptibility testing revealed complete resistance to piperacillin and imipenem (100% each), followed by piperacillin-tazobactam and meropenem (98.08% each), ciprofloxacin (97.12%), ceftazidime (95.19%), levofloxacin (94.23%), and cefepime (87.50%).Aztreonam demonstrated the highest susceptibility (83.65%).ESBL production was detected in 7 (6.73%)isolates, whereas MBL production was identified in 80 (76.92%) isolates.Biofilm formation was observed in 54 (51.92%) isolates by the Christensen's tube method and in 23 (22.12%) isolates by the CRA method. ConclusionsA significant occurrence of multidrug-resistant P. aeruginosa was found among those who had VAP.Extensive antimicrobial resistance, high MBL production, and frequent biofilm formation highlight the therapeutic obstacles linked to these infections.Continuous surveillance of antimicrobial resistance, strict infection-control measures, and judicious antibiotic use are essential to reduce the transmission of resistant strains and improve patient outcomes.