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. 2015 Nov 21;8(11):e25867.
doi: 10.5812/jjm.25867. eCollection 2015 Nov.

Bactericidal and Antibiotic Synergistic Effect of Nanosilver Against Methicillin-Resistant Staphylococcus aureus

Khalid A Ali Abdel Rahim  1 , Ahmed Mohamed Ali Mohamed  2
Affiliations

Bactericidal and Antibiotic Synergistic Effect of Nanosilver Against Methicillin-Resistant Staphylococcus aureus

Khalid A Ali Abdel Rahim et al. Jundishapur J Microbiol. .

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.

Objectives: The aim of this study was to evaluate the bactericidal and antibiotic synergistic effect of silver nanoparticles (Ag-NPs) against MRSA.

Materials and 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.

Keywords: Ag-NPs; Antibiotics; Methicillin-Resistant Staphylococcus aureus; Nanosilver.

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Figures

Figure 1.
Figure 1.. Colony-Forming Capacity Assay
1) Positive control, 2) growth at concentration of 12.5 µg/mL of Ag-NPs,3) growth at 25 µg/mL, 4) growth at concentration of 50 µg/ml, 5) growth at 100 µg/mL, 6) negative control. The MRSA isolates were inhibited at the concentration of 100 µg/mL at 105 CFU where no visible bacterial growth was observed in the agar plates.
Figure 2.
Figure 2.. Methicillin-Resistant Staphylococcus aureus Growth Curve With Different Concentrations of Silver Nanoparticles
Figure 3.
Figure 3.. Average Inhibition Zone (mm) In the Presence of an Antibiotic, and Antibiotic Plus Silver Nanoparticles
Figure 4.
Figure 4.. Synergistic Effect of Nano-Silver (Ag-Nps) With Clindamycin
Figure 5.
Figure 5.. Inhibition of Methicillin-Resistant Staphylococcus aureus Biofilm Formation Determined Using the Tissue Culture Plate Method
See this image and copyright information in PMC

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