Antimicrobial gradient strips

Strains were screened for resistance to antibiotics by agar disk diffusion on Iso Sensitest media (Iso Sensitest Agar, Oxoid, Basingstoke, UK). Zones of inhibition were evaluated against twelve antibiotic (Oxoid, Basingstoke, UK). The following antibiotic discs were used: chloramphenicol (30 g), erythromycin (15 g), fusidic acid (10 g), oxacillin (1 g), penicillin G (1 unit), streptomycin (10 g), tetracycline (10 g), cefoxitin (30 g), gentamicin (10 g), vancomycin (5 g), cefepime (30 g), and mupirocin (20 g). The minimum inhibitory concentrations (MICs) to oxacillin were additionally evaluated using "MIC evaluators", antimicrobial gradient strips designed for accurate minimum inhibitory concentration values (Oxoid Ltd., Basingstoke, UK). The categories susceptible, intermediate resistant or resistant were assigned on the basis of the Clinical and Laboratory Standards Institute (CLSI) antimicrobial susceptibility testing standards.