- Prior Antibiotic Usage: Patients who have received (within 48 hours of study entry) a systemic anti-staphylococcal antibiotic other than vancomycin for longer than 24 hours, unless the patient was considered to have failed that regime ie a documented treatment failure (ie 3 days’ treatment and not responding) or the Staphylococcus is resistant to the antibiotic in vitro (e.g. the patient is initially treated with flucloxacillin but the isolate subsequently identified as resistant) – in such cases the antibiotic must be changed to vancomycin to enter the study.