Comparison of the Antibacterial Effects of Nanosilver With 18 Antibiotics on Multidrug Resistance Clinical Isolates of Acinetobacter baumannii

Background: Acinetobacter baumannii plays a significant role in nosocomial infections. Multidrug-resistant A. baumannii is recognized to be among the most difficult antimicrobial-resistant Gram-negative bacilli to be controlled and treated. For this reason we examined the efficacy of nanosilver material with strong disinfectant properties against different types of bacteria. Objectives: The purpose of this study was to examine the antibacterial activity of silver nanoparticles and compare them with some antibiotics against clinically isolated A. baumannii bacteria. Materials and Methods: 60 A. baumannii strains were isolated from clinical specimens of university hospitals in Tehran province of Iran. The susceptibility test against 18 different antibiotics was investigated by disk diffusion methods. Colloidal nanosilver with about 6-34 nm particle size was prepared by chemical method. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) effect of nanosilver on A. baumannii were assessed at serially diluted nanosilver concentrations and compared to different antibiotics. Results: The findings showed a 100% resistance of A. baumannii to different antibiotics, including piperacillin, cefixime, ceftazidime, ceftizoxime, cephepim and clavulanat, and more than 90% resistance against imipenem, cefotaxime, ceftriaxone, ciprofloxacin and cotrimoxazole and lower resistance was seen against nitrofurantoin (62.8%), gatifloxacin (56.85%), levofloxacin (55.18%), gentamycin (29.32%), piperacillin/tazobactam (13.34%), meropenem (13.16%) and amikacin (12.07%). MIC and MBC mean value of nanosilver dilutions were determined as 27.34 ppm and 54.68 ppm, respectively. All isolates (100%) were susceptible to more than MIC of nanosilver in contrast showed high resistance to multiple classes of antibiotics. Conclusions: We conclude that nanosilver is a strong bactericidal agent to Multidrug resistant A. baumannii bacteria, so it can be useful to prevent a variety of nosocomial infections.