Abstract
Methicillin-resistant Staphylococcus aureus is the cause of nosocomial and community-acquired infections. This study aimed to evaluate the effect of zinc oxide and silver nanoparticles (ZnO-Ag NPs) on biofilms formation and icaA gene expression in methicillin-resistant S. aureus (MRSA). In this study, three standard strains (ATCC 43300, 25923, and 29913) and a clinical isolate are included. The minimum inhibitory concentration (MIC) of nanoparticles was determined by microdilution broth method. The antibacterial effects of ZnO-Ag NPs either alone or in combination with each other were compared with vancomycin (as the control group). The effect of MIC and sub-MIC concentrations of ZnO-Ag NPs on biofilm formation was determined by the microtiter plate method. The expression level of the icaA gene was assessed by real-time PCR LightCycler® 96 software (Version 1.1.0.1320, Roche, Germany). technique. All experiments were repeated three times. Data were analyzed using SPSS software through ANOVA and t-test. The P-value of less than .05 was considered as statistically significant. The average MICs of ZnO, Ag, and ZnO-Ag NPs compounds were 393.2, 179.8, and 60.8 μg/ml, respectively. The compound of ZnO-Ag NPs had a synergistic effect against all isolates. ZnO-Ag NPs decreased the biofilm formation rate at MIC and sub-MIC concentrations (P < .001). Sub-MIC ZnO-Ag NPs concentration significantly reduced the icaA gene expression in S. aureus strains (P < .03). The sub-MIC concentration of ZnO-Ag NPs reduced biofilm formation rate and icaA gene expression in Staphylococcus aureus strains compared with vancomycin. It can be used to cover medical devices after examining more clinical isolates to prevent bacterial colonization.
Different bacterial gene expression patterns and attenuated host immune responses are associated with the evolution of low-level vancomycin resistance during persistent methicillin-resistant Staphylococcus aureus bacteraemia
