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Phenotypic detection of methicillin resistance in Staphylococcus aureus by disk diffusion testing and Etest on Mueller-Hinton agar.

ABSTRACT: Cefoxitin is increasingly recommended for detection of methicillin resistance in Staphylococcus aureus (MRSA) when using disk diffusion testing. In this study, 95 mecA-negative S. aureus isolates and a highly genetically diverse collection of mecA-positive S. aureus types (n=50) were used to investigate the influence of technical factors such as disk potency, incubation time, and temperature on Mueller-Hinton agar. The use of cefoxitin MIC testing by Etest for the same purpose was investigated under similar conditions. For disk diffusion, the accuracy was high at both 35 degrees C and 36 degrees C using overnight incubation, while incubation at 30 degrees C or 37 degrees C was associated with slightly lower accuracy. Increasing incubation times from 18 to 24 h did not improve accuracy at either temperature. Cefoxitin Etest MICs for mecA-positive strains were 6 mg/liter or higher, while cefoxitin Etest MICs for mecA-negative strains were 4 mg/liter, corresponding to S>or=22 mm and Ror=17 mm and R

SUBMITTER: Skov R

PROVIDER: S-EPMC1698388 | biostudies-other | 2006 Dec

REPOSITORIES: biostudies-other

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