Surveying drug resistance of Staphylococcus aureus strains resistant to the antibiotic vancomycin in some hospitals in Rasht

Staphylococcus aureus, as a most important cause of nosocomial and community-acquired infections, shows resistance to a wide range of antibiotics. The aim of this study was the phenotypic and molecular study of clinical isolates of vancomycin-resistant Staphylococcus aureus isolated from hospitals in Rasht in a six- month period (February 2015 to July 95).
217 clinical samples were collected from different wards of hospitals in Rasht. Staphylococcus aureus isolates were identified by biochemical tests. To determine microbial resistance of the strains to antibiotic vancomycin, phenotypic tests of disk diffusion (according to the CLSI), and minimum Inhibitory concentration in microdilution broth method were used. Also, the presence of VanA gene, encoding resistance to the antibiotic vancomycin in separated isolate was evaluated by PCR method.
67 Staphylococcus aureus were identified. In the test determining resistance to the antibiotic by disk diffusion method, the results in terms of resistance rate against antibiotics was as follow: 10.5% chloramphenicol, 25.37% gentamicin, 37.32% tetracyclin, 38.80% vancomycin, 44.7% oxacillin and 100% penicillin. In the microdilution broth, 22.4% of the samples showed resistance to vancomycin. In PCR, no band was observed for genes VanA.
It is recommended that in molecular studies, the presence of genes VanA and VanB is assessed; since the resistance could be related to the presence of VanB gene.