Document Type : New and original researches in the field of Microbiology.
Authors
1
Department of Microbiology, College of Medicine, University of Babylon, Babylon, Babylon, Iraq
2
DNA Research Center, University of Babylon, Babylon, Iraq
Abstract
Background: Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen responsible for severe hospital-acquired infections. Rising antibiotic resistance necessitates alternative antimicrobial strategies, such as silver nanoparticles (AgNPs). Objective: To evaluate the antibacterial activity of different AgNP concentrations compared with selected conventional antibiotics against P. aeruginosa clinical isolates. Methodology: Five Pseudomonas aeruginosa isolates were tested in this study. The work was conducted at the Microbiology Laboratory, Al-Turki Hospital, Hillah, Babylon, Iraq, between September 2024 and May 2025. A total of 66 P. aeruginosa isolates were initially obtained from clinical specimens, including wound swabs, burn exudates, and respiratory secretions, collected from patients with hospital-acquired infections. From these, five representative isolates with distinct antibiotic resistance profiles were selected for detailed testing. Silver nanoparticles (AgNPs) at concentrations of 31.25–500 µg/mL were prepared by serial dilution and evaluated using the agar well diffusion method. Antibiotic susceptibility was determined using the Kirby–Bauer disc diffusion method with Colistin, Norfloxacin, Aztreonam, Cefepime, and Tobramycin. Inhibition zones were measured after 24 h incubation at 37 °C. Results: AgNPs showed a concentration-dependent antibacterial effect. The highest inhibition zones were observed at 500 µg/Ml (17.2±1.9 mm) and 250 µg/mL (16.0±1.2 mm). Lower concentrations (31.25–125 µg/mL) produced smaller but measurable zones (10.0–14.4 mm). All isolates were resistant to Colistin, Cefepime, Aztreonam, and Tobramycin, while Norfloxacin inhibited only two isolates (25 mm). Conclusion: AgNPs demonstrated superior antibacterial activity compared with most tested antibiotics, indicating their potential as alternative or adjunctive agents against multidrug-resistant P. aeruginosa. Further studies on safety, mechanisms, and clinical applicability are recommended.
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