Iranian Journal of Medical Microbiology

Background and Objective: Ventilator-associated pneumonia (VAP) is a severe infection occurring in mechanically ventilated ICU patients with Pseudomonas aeruginosa being the leading etiology. This pathogen frequently develops resistance to multiple antibiotic, including through biofilm formation. Hence, this study aims to evaluate the association between in-vitro biofilm production and antimicrobial susceptibility of Pseudomonas aeruginosa in the planktonic state.
Methods This is a pilot study analyzing seven P. aeruginosa strains isolated from VAP patients at Dr. Soetomo General Hospital, Surabaya, Indonesia. Bacteria were identified from endotracheal aspirates using Gram staining, oxidase testing, and the VITEK® 2 system. Biofilm production was assessed via crystal violet staining, and antimicrobial susceptibility was determined by broth microdilution. Statistical analysis was performed with the Mann-Whitney nonparametric test using GraphPad Prism 9 software.
Results & Conclusion: Significant differences were observed in the biofilm production and antimicrobial susceptibility of P. aeruginosa isolates from VAP patients against ceftazidime, piperacillin-tazobactam, cefepime, aztreonam, levofloxacin, and piperacillin. Strong biofilm producers showed higher resistance, especially to ceftazidime, piperacillin-tazobactam, and piperacillin, while weak biofilm producers had minimal resistance, except to ciprofloxacin, ticarcillin-clavulanate, and levofloxacin. Colistin showed MIC values of ≤2 µg/mL against all isolates. Our findings indicate biofilm formation as a critical factor influencing resistance, emphasizing the need to consider biofilm-producing capacity when selecting treatment strategies for VAP caused by P. aeruginosa.