To the Editor.
—The recent article of Trump et al, published in the Archives (1982;142:583-586), showed the importance of Staphylococcus epidermidis in CSF infections in patients with subcutaneous reservoirs and ventricular catheters.It was stated that "the pattern of antibiotic sensitivity using a standard in vitro disk method provided useful information regarding the clinical importance of an S epidermidis isolate." Did they indeed use a disk diffusion test and read minimal inhibitory concentrations (MICs) from an interpretive chart or, more likely, did they use a broth dilution technique for MICs?They changed their prophylactic coverage from cephalothin sodium and cephalexin monohydrate therapy to nafcillin sodium therapy because they wanted to use a drug to which the S epidermidis isolates were sensitive. A dose of 2 g of nafcillin sodium intravenously at the time of preparation of the skin for surgery and 1 g every four hours for 24 hours after