In vitro efficacy of colistin against multidrug-resistant Pseudomonas aeruginosa in burn patient by minimum inhibitory concentration with broth dilution

Background: Pseudomonas aeruginosa strains cause 86% of sepsis mortality in burn victims. Therefore, to combat the multi-drug resistance in Pseudomonas aeruginosa, colistin is the new drug, and it has recently been introduced. To analyze the in vitro efficacy of colistin against multidrug-resistant Pseudomonas aeruginosa in burn patients by determining the minimum inhibitory concentration with broth dilution. Material And Methods: The cross-sectional study was performed from March 2021 to February 2022 in the Burn Centre at Nishter Hospital in Multan, Pakistan. 300 burn patients (≥20% burn) were selected, and their pus samples were collected and processed in the microbiology laboratory. The Kirby-Bauer disc diffusion method was applied to check the antibiotic susceptibility against isolated strains. The colistin sensitivity against multi-drug resistant (MDR) strains was estimated by employing the broth dilution method at two-fold serial dilutions from 0.5 µg/mL to 0.003 µg/mL. Results: 124 (55.3%) strains were identified as Pseudomonas aeruginosa, while the remaining strains were identified as Escherichia coli (13.0%), Streptococci (13.0%), Klebsiella pneumoniae (8.9%), Staphylococci (6.6%), and Candida albicans (2.2%). All isolated strains of Pseudomonas aeruginosa showed resistance against antibiotics: aztreonam (60.4%), cefepime (72.5%), ceftazidime (71.7%), ciprofloxacin (62.0%), imipenem (33.0%), levofloxacin (58.0%), meropenem (19.3%), piperacillin/tazobactam (66.1%), and tobramycin (63.7%). The significantly calculated MIC value of colistin against MDR strains was 0.35-0.5 mg/L (CLSI and EUCAST recommended value = ≤2 mg/L). Conclusion: Colistin can be a good option to treat nosocomial infections of MDR Pseudomonas aeruginosa in burn patients. Keywords: Burn patients, Colistin, Multi-drug resistance, Minimum inhibitory concentration