Synergistic effect of silver nanoparticles (AgNPs) and gentamicin against clinical isolates of Pseudomona aeruginosa

Pseudomona aeruginosa is one of the most important opportunistic pathogens and is one of the main causes of nosocomial infections. Antibiotic therapy has faced with serious problem due to worldwide antibiotic resistance of this organism. The purpose of this study was to evaluate the anti-bacteial effects of AgNPs on Gentamicin against clinical isolate of P. aeruginosa. Sixty strains of P. aeruginosa were isolated from blood, wound, respiratory specimens collected from hospitalized patients within Tehran hospitals. All isolates were first confirmed using standard bacteriologic tests. Standard Kirby- Bauer agar diffusion method was used to evaluate the gentamycin resistance pattern of isolates and also their sensitivity pattern to different concentrations of AgNPs. Finally the effects of different combinations of gentamycin and AgNPs on P. aeruginosa were tested and the results were analyzed by statistical methods. More than 56% of isolates were resistant to gentamicin, and 13% were mentioned as intermediate according to CLSI guidelines. 30% of isolates were sensitive to this antibiotic. Almost all isolates were sensitive to AgNPs at concentrations of up to 10 μg/ml. The ratio of 50:50 of gentamycin and AgNPs sowed efficacy against all clinical isolates and standard. we concluded that AGNps enhanced anti-bacterial effects of gentamycin at different ratio of two components. The best effects observed when antibiotic and AgNPs were mixed equally at their MIC level. We assumed that different size of AgNPs should be tested with antibiotic before final recommendation.