A sensitive bioassay for teicoplanin in serum in the presence or absence of other antibiotics.

A teicoplanin bioassay has been developed that is accurate, sensitive, and reliable. A linear relationship is obtained between the diameter of the zone of inhibition and log10 teicoplanin concentration in human serum over the range of 0.15 or 1.25 to 96 micrograms/ml using wells or paper filter disks, respectively. The assay medium devised consists of 50 g BBL Mueller-Hinton II Agar, 30 g NaCl, 8 g CaCl2, and 1.0 g citric acid (monohydrate) per liter of deionized water (resulting pH 5.1 +/- 0.1) and the assay organism Bacillus subtilis ATCC 6633. This system allows the assay of teicoplanin in the presence of commonly used aminoglycosides and in the presence of beta-lactams after inactivation by beta-lactamase. Additionally, it has the potential to be used in the presence of rifampin by using a rifampin-resistant strain of B. subtilis.