title: Bactericidal and Antibiotic Synergistic Effect of Nanosilver Against Methicillin-Resistant Staphylococcus aureus.
abstract: BACKGROUND
  Methicillin-Resistant Staphylococcus aureus (MRSA) are bacteria responsible for several difficult-to-treat infections in humans. These strains have developed, through the process of natural selection. Infections by MRSA are more difficult to treat with standard types of antibiotics and thus more dangerous to human health.
  
  
  OBJECTIVE
  The aim of this study was to evaluate the bactericidal and antibiotic synergistic effect of silver nanoparticles (Ag-NPs) against MRSA.
  
  
  METHODS
  Methicillin-Resistant Staphylococcus aureus strains were isolated from clinical samples and identified, and their susceptibility was tested using the MicroScan® WalkAway-96® SI System. minimum inhibitory concentration (MIC) was determined by a microdilution method. Time kill assay was performed by exposing the MRSA isolates to different concentrations of Ag-NPs and monitoring bacterial growth, by measuring optical density at 600 nm. Tissue culture plate was used for determination of the efficacy of Ag-NPs and their combination with antibiotics in the elimination of formed biofilm.
  
  
  RESULTS
  The MIC value of Ag-NPs against MRSA was 100 μg/mL. Methicillin-Resistant Staphylococcus aureus cells were treated with 50, 100 and 200 µg/mL of Ag-NPs and inhibited bacterial growth so that after four hours, almost all treated MRSA cells were dead. All combinations showed effectiveness against MRSA. It was observed that MRSA did not show inhibition zones with ampicillin alone.
  
  
  CONCLUSIONS
  Silver Nanoparticles have high therapeutic activity against MRSA, thus can be suggested as an alternative or adjuvant with antibiotics for MRSA treatment. Further studies are required to understand the synergistic effect of Ag-NPs combinations and to assess the safety and efficacy of new antibiotic-Ag-NPs combinations.
authors: Botany and Microbiology Department, College of Sciences, King Saud University, Riyadh, Saudi Arabia; Botany Department, Central Laboratory of Genetic Engineering, Faculty of Sciences, Sohag University, Sohag, Egypt.
authors: Khalid A Ali
authors: KA
authors: Abdel Rahim
authors: Department of Medical Laboratory Technology, College of Applied Medical Sciences, University of Dammam, Hafr Al Batin-319 91, Saudi Arabia.
authors: Ahmed Mohamed
authors: AM
authors: Ali Mohamed
keywords: Ag-NPs; Antibiotics; Methicillin-Resistant Staphylococcus aureus; Nanosilver