Comparison of two antimicrobial susceptibility tests, disk diffusion and E-test for determining oxacillin and vancomycin susceptibility

ABSTRACT

Staphylococcus aureus [S. aureus] is an important cause of nosocomial infections while recently resistance to oxacillin and vancomycin have been noted in literature. We studied 100 isolates of S. aureus from Emam Khomeini hospital by two antimicrobial susceptibility tests [AST]; disk diffusion test [DDT] and E-test to determine the resistance to oxacillin [according to NCCLS comment] and vancomycin. There were no resistant S. aureus to vancomycin neither in DDT nor in E-test, however, there were 42% oxacillin-resistance S. aureus in both techniques. The results showed high prevalence of methicillin-resistant Staphylococcus aureus [MRSA] in Emam Khomeini hospital. The highest S. aureus infection detected from internal wards [26%], heart surgery ward [23%], sampling sites in wound [26%], surgical incision [20%], blood culture [17%] and prosthetic sites [14%]. We should pay further attention to high risk wards and sites to control hospital infections. According to our results, there was a high coincidence between two AST methods: