Effect of teicoplanin on isolation of Staphylococcus aureus from blood culture media.

Intraoperative bacteraemia has been used as an indicator of the efficacy of prophylactic antibiotics. Two clinical isolates of Staphylococcus aureus in nutrient broth, with or without human serum, were exposed to teicoplanin (50 mg/L) and, either immediately or after 30 min, inoculated into blood culture bottles. Bottles with and without resin were used and the experiment was repeated five times with one strain. In the absence of teicoplanin, an inoculum of 10 cfu/mL produced growth in both resin and non-resin bottles. In the presence of teicoplanin, an inoculum of at least 10(5) cfu/mL was required in non-resin bottles to obtain growth, but this was reduced to 10(2)-10(3) cfu/mL for resin bottles. Intraoperative blood cultures overestimate the efficacy of bacterial killing by prophylactic antibiotics during surgery.