Evaluation of the antimicrobial activity of Arnebia euchroma extract and its influence on quorum sensing gene expression in Pseudomonas aeruginosa

Abstract

Background: Antibiotic resistance in Pseudomonas aeruginosa has become a significant public health concern, particularly in burn patients. This study aimed to evaluate the effect of Arnebia euchroma extract on the expression of the lasR and lasI genes, which are crucial for the pathogenicity of this bacterium. Methods: Five P. aeruginosa strains were isolated from burn wounds, identified with selective media and differential tests. The methanolic extract of A. euchroma was prepared by maceration and tested for antimicrobial activity. Antibiotic susceptibility was assessed using the disc diffusion method. The presence of lasI and lasR genes in clinical strains was confirmed by PCR, and their expression levels were quantified by Real-Time PCR. Active compounds in the extract were identified using gas chromatography-mass spectrometry. Results: The A. euchroma root extract exhibited significant antibacterial effects, forming clear inhibition zones on agar plates. Its minimum inhibitory concentration ranged from 62.5 to 250 mu g/mL, while the minimum bactericidal concentration was between 125 and 250 mu g/mL. All tested P. aeruginosa isolates were positive for the lasI and lasR genes, with gene expression significantly reduced in the presence of the extract. The extract inhibited over 75 of lasI and lasR expression, comparable to tobramycin. Diacetone alcohol, alpha-terpinenyl acetate, and xanthosine were identified as the most abundant compounds in the root. Conclusion: The findings suggest that A. euchroma extract has potential as an antimicrobial and quorum sensing inhibitor. However, further studies with larger strain collections and in vivo validation are needed to confirm its therapeutic relevance.