Evaluation of vancomycin resistance by Phenotypic and genotypic methods among S. aureus strains isolated from patients

Staphylococcus aureus is one the main human pathogens which is involved in a wide range of infections. Although, Vancomycin is one of the best drugs to treat infections which are caused by S.aureus, indiscriminate use of vancomycin causes resistant strains. The aim of this study was to investigate the possible presence of vancomycin resistant strains and determination of their antibiogram patterns.
Material and In the present study, Staphylococcus aureus was isolated from the 100 clinical specimens. All the isolates were identified using gram staining, catalase test, tube coagulase test, growth on Mannitol salt agar medium, and the DNase test. Susceptibility of the isolates against 9 different antimicrobial agents was investigated using the standard disk diffusion. MIC values of vancomycin was also tested by agar dilution methods, according to the CLSI. Moreover, Polymeras Chain Reaction (PCR) was performed to detect the vanA gene.
All of the Staphylococcus aureus isolates were sensitive to vancomycin (MIC value ranged from 0.125 to 2 μg/mL). Ampicillin and vancomycin revealed the highest and lowest resistance rates with 80% and 1%, respectively.
Fortunately,vancomycin resistant staphylococcus aureus was not found among the tested isolates in this study. Therefore, vancomycin can still be used in treatment of Staphylococcus aureus infections.