title: Revised interpretation of oxacillin MICs for Staphylococcus epidermidis based on mecA detection.
abstract: In 1992 and 1993, at The Ohio State University Medical Center, a larger proportion of Staphylococcus epidermidis strains required oxacillin MICs of 1 to 2 micrograms/ml than did Staphylococcus aureus strains. mecA genotype was correlated with antimicrobial susceptibility for selected clinical S. epidermidis strains. All 14 strains that required oxacillin MICs of < or = 0.25 microgram/ml and 2 of 5 strains that required oxacillin MICs of 0.5 microgram/ml were susceptible by 1-microgram oxacillin disk test and were mecA negative. Three of 5 strains that required oxacillin MICs of 0.5 microgram/ml and all 18 strains that required oxacillin MICs of > or = 1.0 microgram/ml were resistant by oxacillin disk test and were mecA positive. Current National Committee for Clinical Laboratory Standards MIC interpretive criteria may underestimate methicillin resistance among S. epidermidis strains.
authors.affiliation: Department of Internal Medicine, Ohio State University College of Medicine, Columbus 43210, USA.
authors.forename: C L
authors.initials: CL
authors.lastname: McDonald
authors.forename: W E
authors.initials: WE
authors.lastname: Maher
authors.forename: R J
authors.initials: RJ
authors.lastname: Fass
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D005838:Genotype; D008826:Microbial Sensitivity Tests; D010068:Oxacillin / Q000494:pharmacology*; D013212:Staphylococcus epidermidis / Q000187:drug effects* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D010068:Oxacillin