الفهرس 
Staphylococcus aureus and Methicillin- Resistant Staphylococcus aureusOnly 14 pages are availabe for public view
 |  | from | 182 |  |  |
| | | from | 182 | | |
Abstract
Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of community-acquired and hospital-acquired infections with high rates of mortality, morbidity, and medical expenses.
Vancomycin is one of the main curative measures for MRSA infections. However, isolates of S. aureus that are resistant to vancomycin have emerged in recent years. To prevent and treat infections caused by MRSA strains, it is essential to introduce and describe novel medicines that are both efficient and safe.
Nanoparticles are suitable platforms for fighting bacterial infections because of the easy manipulation of their shape, size, and surface chemistry. Nanoparticles can also play a role as a “medium and carrier” of antibiotics.
Gold nanoparticles (AuNPs) have displayed uniquely advantageous antimicrobial activity. Gold possesses very stable chemical properties; It is non-toxic, and it has good biocompatibility. AuNPs represent excellent candidates for antimicrobial agents’ delivery at the site of infection and are efficient in sustaining antibiotic release over a prolonged period, resulting in enhanced antibiotic efficacy. Thus, the conjugation of antibiotics to the surface of AuNPs results in decreasing the toxicity of nanoparticles and increasing the activity of antibiotics at relatively low concentrations.
This work aims to study the effect of gold nanoparticles in enhancing vancomycin potential against MRSA clinical isolates from different types of infections.
Thirty MRSA isolates were subjected to conventional identification. Microwave-assisted synthesis of AuNPs and vancomycin conjugated gold nanoparticles (V-AuNPs) were done and subsequently characterized by visual observation of color change, uv- visible (UV-Vis) spectroscopy, high-resolution transmission electron microscopy (HRTEM), zeta potential analysis and dynamic light scattering (DLS) measurement, x-ray diffraction (XRD) analysis, and fourier transform infrared spectroscopy (FTIR). This method has the advantage of a short reaction time.
MRSA isolates were tested to determine the minimal inhibitory concentration (MIC) of vancomycin, AuNPs, and V-AuNPs using the microtiter broth dilution method.
Twenty-seven (90%) MRSA isolates were susceptible to vancomycin, and three (10%) showed intermediate susceptibility. MIC ranged from 0.48 to 7.8 μg /ml, with a mean MIC ± SD of 2.68 ± 2.07 μg /ml, an IC50 of 1.95 μg /ml, and an IC90 of 3.9 μg /ml. Thirty (100%) MRSA isolates were susceptible to AuNPs with MIC ranging from 125 to 250 μg /ml, with a mean MIC ± SD of 164.6 ± 62.5 μg /ml, an IC50 of 125 μg /ml and an IC90 of 250 μg /ml. Also, thirty (100%) MRSA isolates were susceptible to V-AuNPs with MIC ranging from 0.06 to 1.95 μg /ml, with a mean MIC ± SD of 0.40 ± 0.46 μg /ml, an IC50 of 0.24 μg /ml and an IC 90 of 0.48 μg /ml.
The intermediate-susceptible isolates to vancomycin were converted to be susceptible to V-AuNPs at much lower doses of vancomycin, where intermediate susceptible isolates to vancomycin showed mean MIC ± SD as 6.24 ± 2.14 μg /ml for vancomycin alone, while showing mean MIC ± SD as 1.17 + 0.74 μg /ml for V-AuNPs, revealing the relevant promising effect of conjugation of vancomycin to AuNPs.
A High statistically significant difference was found between the MIC values of vancomycin and V-AuNPs and between AuNPs and V-AuNPs.
Concerning the cytotoxicity of V-AuNPs to HFF-1 cells, using a concentration of 2 µg/ml of V-AuNPs gave 100% viability of the cells, while raising the concentration to 33.85± 3.16 µg/ml, viability was dropped to 50%, and raising the conc. to 250 µg/ml, viability was dropped to 4.72%, indicating that the used conc. range in this study was safe for the HFF-1 cells.
The current study concluded that V-AuNPs display superior antibacterial activity as compared to vancomycin and AuNPs alone as a potential effective therapy against MRSA