Evaluation of Trimethoprim Nanoemulsion for Combating Antibiotic Resistant Proteus mirabilis in Urinary Tract Infections

Background and Aim: Nanoemulsion technology is considered one of the most advanced and targeted drug delivery systems.This study aimed to evaluate the efficacy of a trimethoprim-based nanoemulsion against Proteus mirabilis isolated from urinary tract infections (UTIs). Materials and Methods:A total of 300 urine samples were collected from patients with clinically diagnosed UTIs at Azadi Teaching Hospital.Samples were cultured on blood agar and MacConkey agar.Phenotypic identification was performed, and P. mirabilis was confirmed by detection of the 16S rRNA gene.Antibiotic susceptibility was assessed using the Kirby-Bauer disk diffusion method.Trimethoprim nanoemulsions were prepared through phase diagram construction, characterized by Fourier-transform infrared spectroscopy (FTIR), zeta potential, and field emission scanning electron microscopy (FESEM), and evaluated for stability and antimicrobial activity.Results: Of 175 culture-positive samples, 50 (28.6%)yielded P. mirabilis.PCR confirmed all isolates by amplification of a single 1500-bp 16S rRNA gene fragment.Antimicrobial susceptibility testing showed complete resistance (100%) to ampicillin, 50% resistance to trimethoprim, nalidixic acid, and ciprofloxacin, and 30% resistance to gentamicin.FTIR analysis indicated no major chemical interactions between trimethoprim and excipients, supporting drug stability.FESEM imaging demonstrated a uniform spherical morphology of the nanoemulsion droplets, consistent with high stability and bioactivity.The mean inhibition zone diameter of the trimethoprim nanoemulsion against P. mirabilis was 41.5 mm, significantly greater than that of pure trimethoprim (p < 0.001). Conclusion:The All P. mirabilis isolates were fully susceptible to the trimethoprim nanoemulsion, highlighting its potent antibacterial activity and potential as a therapeutic strategy against multidrug-resistant strains.