Evaluating Susceptibility of Environmental Isolates of Pseudomonas aeruginosa to Chlorhexidine Gluconate and Aqueous Extract of Peganum harmala

Background and Objective: Pseudomonas aeruginosa is an important case of nosocomial infections and a major health problem. The increased emergence of resistance to antibiotics and disinfectants among these bacteria, necessitates the production of new antimicrobials with wider activity and low toxicity. This study was carried out to evaluate inhibitory effects of chlorhexidine gluconate and extract of Peganum harmala on multi-drug resistant (MDR) P. aeruginosa. Material and Methods: 39 P. aeruginosa strains were isolated from 114 environmental samples. After identifying MDR strains, minimal inhibitory concentration (MIC) of chlorhexidine gluconate (20%) and P. harmala extract against the isolates was determined by broth microdilution method. Results: Overall, 27 (69.2%) P. aeruginosa isolates resistant to quinolones, aminoglycoside, cephems and carbapenems were reported as MDR strains. The MIC of chlorhexidine gluconate was ≥ 1000μg/ml, which was 4-fold higher than the MIC of P. harmala extract (MIC = 500μg/ml). MIC of chlorhexidine gluconate and P. harmala extract against P. aeruginosa isolates differed significantly (P=0.01). Conclusion: Compared to chlorhexidine gluconate, P. harmala extract has a higher antibacterial effect on MDR P. aeruginosa isolates from environment. Further research is required to verify the efficacy of this plant extract for disinfection of equipment in local clinics and laboratories