IS S AUREUS RESISTANT TO VANCOMYCIN?
Staphylococcus aureus may be developing resistance to vancomycin, warned the Centers for Disease Control and Prevention (CDC) in a report of the fourth known case of vancomycin-resistant S aureus. This is somewhat alarming because nosocomial methicillin-resistant S aureus (MRSA) is already common, and vancomycin is the last line of defense against it. The case involved a 63-year-old woman with end-stage renal disease who had a history of frequent hospitalizations and intermittent treatment with vancomycin. Her most recent hospitalization (in April 1999) was for MRSA bacteremia, which had developed despite nearly two weeks of vancomycin therapy. The patient continued to receive vancomycin in the hospital. Nevertheless, a blood culture 13 days after admission grew S aureus with a minimum inhibitory concentration (MIC) of 4 g/mL. The patient’s median serum vancomycin concentration was 12.7 g/mL at that time. Three subsequent blood cultures over the next three days grew S aureus with MICs
