Introduction: In the 1950s vancomycin was introduced as an effective antibiotic for curing infections caused by methicillin Resistant Staphylococcus Aureus. Three decade after using vancomycin, Resistant coagulase negative Staphylococcus to this antibiotic was reported. In this study, we evaluate the Staphylococcus aurous Resistant to vancomycin.Materials and methods: During this invesitigatin which lasted for 6 months, 50 Staphylococcus aurous samples were taken from burn wards of each of two Imam - Reza and Gaem hospitals, Mashhad. All selected samples were Resistant to methicillin and their MIC to vancomycin was determined.Results: Of 50 separated bacteria from Imam-Reza and Gaem hospitals subjects, 4 patients had MIC equal to 12.5 mg/ml. In isolated samples from Gaem hospital, one case has MIC equal to 12.5 mg/ml. Conclusion: With respect to expanding the Resistant toward vancomycin, thus it is recommended to inhibit the resistance of this organism in the wards.

Chitosan (Cs) was extracted from shrimp shell and its derivative forms including N-alkyl (AlkCs) and nanoparticles (CsNPs) were prepared. First, the properties of nanoparticles were determined by dynamic light scattering (DLS) and the morphology of nanoparticles and N-alkylated by scanning electron microscopy (SEM). Then their antibacterial activity was evaluated by the test of minimum inhibitory (MIC) and lethal (MBC) concentration, diffusion on agar by disk, permeability of cell membrane by measurement of cytoplasmic beta-galactosidase release (ONPG). The type of apoptosis cell death was also examined by DAPI staining and changes in cell surface integrity by atomic force microscopy (AFM). The results showed that the nanoparticles are spherical with an average hydrodynamic diameter of 240 nm. N-alkyl had a rough surface structure compared to native chitosan. At the least of MIC (78 μg/ml) and MBC (100 μg/ml) points were observed for CsNPs (P < 0. 05). Nanoparticles and N-alkyl of chitosan showed the highest diameter of growth inhibition zone at 1250 concentration compared to other disks (p <0. 05). Outer membrane permeability of derivative forms of chitosan showed significant differences with native chitosan and cells of control. DAPI staining test showed higher cell death of chitosan-derived forms. DAPI staining test showed higher cell death of derivative of chitosan. The images obtained from AFM showed a change in the membrane integrity of the treated cells compared to spherical and clustered of control cells. Thus, the antibacterial properties of native chitosan improved by physical and chemical modification.