Incorporating resins in blood culture media can effectively reduce the activities of several antibiotics. It was shown that the activities of some generally used antibiotics decreased by 80 to 90% within 2 h in Bactec Plus Aerobic/F resin-containing culture medium, Bactec vials containing resins were still found to be positive for bacteria when antibiotics were present. The addition of S-lactamase shortened the detection time irrespective of the presence of resins.