Evaluation of antibacterial and antibiofilm efficacy of gentamicin-loaded solid lipid nanoparticles (GM-SLNs) against Acinetobacter baumannii infections

Abstract

Acinetobacter baumannii has become a notable “superbug” due to its rapid development of resistance to multiple classes of antibiotics. This study aimed to evaluate the antibacterial and antibiofilm effectiveness of gentamicin-loaded solid lipid nanoparticles (GM-SLNs) in treating infections caused by A. baumannii. Nanoparticles were synthesized using the double melt emulsion dispersion method. A. baumannii was isolated from wounds, blood, urine, and sputum through standard microbiological techniques. Antimicrobial susceptibility was tested using the Kirby-Bauer disk diffusion method. The biofilm-forming ability of A. baumannii isolates, the antibacterial activity of GM-SLNs, and the time killing assay were conducted following standard protocols with slight modifications. The impact of GM-SLNs on the expression of biofilm-related genes was analyzed using real-time PCR. A total of 37 A. baumannii strains were isolated from 41 clinical specimens. The most common antibiotic resistances were against gentamicin (GM), ciprofloxacin (CIP), ceftazidime (CAZ), and imipenem (IMP). 80% of the A. baumannii isolates were classified as multidrug-resistant (MDR). GM-SLNs reduced the minimum inhibitory concentrations (MICs) for all A. baumannii strains twofold, fourfold, and even up to eightfold compared to free GM. GM-SLNs were also significantly more effective than free GM in inhibiting biofilm formation in all A. baumannii isolates. Furthermore, the expression of the bap gene was significantly lower in all isolates treated with GM-SLNs compared to those treated with free GM. Overall, GM-SLNs represent a major breakthrough in the fight against A. baumannii and other biofilm-related infections, providing hope for more effective treatment options amid the growing challenge of antimicrobial resistance.