Synergistic Effect of Biogenic Silver Nanoparticles and Antibiotics Against Multidrug-Resistant Pseudomonas aeruginosa

Abstract

Infections caused by Pseudomonas aeruginosa may be either acquired in the community or contracted in a healthcare setting. Multidrug-resistant (MDR) P. aeruginosa is a growing problem; a new treatment approach is required to tackle this. Combination therapy of antibiotics and nanoparticle is thus applied to overcome this problem. Therefore, this study was planned to evaluate the synergistic effect of AgNPs along with different antibiotics against MDR P. aeruginosa. A total of 120 surgical or burn wound samples were collected from a tertiary care hospital. The plates containing the samples cultivated on cetrimide agar were then heated to 37°C. Isolates were identified based on colony shape, Gram staining, and several biochemical tests. A Kirby-Bauer disc diffusion technique antibiogram was conducted following CLSI 2022 recommendations. A minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were also determined. The Agar well diffusion technique and the microdilution method were used to test the antibacterial activity of the AgNPs, respectively. The synergistic effect of antibiotics and AgNPs was estimated by the Checkerboard method. Out of 120 samples, 46 (38.8%) were confirmed positive for P. aeruginosa, and out of that, 33 were confirmed as MDR P. aeruginosa. Seven representative isolates proceeded for further procedures. Antibacterial activity of AgNPs revealed a maximum zone of inhibition of 12 mm at 4 mg/ml and a minimum of 2.5 mm at 1 mg/ml by agar well diffusion method. MIC and MBC of AgNPs showed that all the isolates were inhibited at 250 mg/ml. The FIC index of checkerboard results showed that colistin and gentamicin exhibited complete synergism with AgNPs, while ciprofloxacin showed partial synergism with AgNPs.