In vitro bactericidal and imipenem synergistic effect of nano-silver against multiple drug-resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa ( P. aeruginosa ) is an aerobic gram-negative pathogen. It induces decline of lung functions and increase mortality rate. It has a high antimicrobial resistance rate limiting number of antibiotics which can be used. Evaluation of bactericidal and antibiotic synergistic effect of Nano-silver (Ag-NP) against Multiple drug-resistant P.aeruginosa (MDR P. aeruginosa ). P.aeruginosa were isolated from clinical specimens. MicroScan WalkAway-96SI System was used for laboratory Identification, antimicrobial susceptibility. Minimal inhibitory concentration (MIC) was determined by a microdilution method. Time kill assay determined by incubation MRSA with different concentrations of Ag-NP (0, 50, 100, and 200 μg/ml) in a shaking incubator at 37 °C for 24 h. Growth curves of bacterial cell cultures were attained through repeated measures of the optical density (O.D.) at 600 nm. The disc diffusion method was used to evaluate synergistic of Ag-NP with antibiotics. The MIC value of Ag-NPs against MDR P. aeruginosa was in at of 5 μg/ml. The bacterial growths of cells treated with 1.25, 2.5, 5 and 10 µg/ml Ag-NPs were inhibited. After 4 h, almost all treated bacterial cells were dead. All of the combinations showed significant synergistic effect (P-value 0.003), and the result showed the highest synergism at concentrations of Imipenem at MIC (32 µg/ml) and 16 µg/ml. Nano-Silver has high therapeutic activity against MDR P. aeruginosa, it can be suggested as an alternative or adjuvant with antibiotics for MDR P. aeruginosa treatment. Further studies are required for understand synergistic effect of Ag-NP combining, and assessment of its safety.