Bactericidal activity of teicoplanin in an in-vitro two-compartment kinetic model

The bactericidal activity of teicoplanin was studied in a model system in which antibiotic concentration is continuously varied. A two-compartment open model was used to reproduce, in vitro serum pharmacokinetics of teicoplanin in humans during 24 h after iv administration. Staphylococcal and streptococcal strains of various species were tested. Teicoplanin showed rapid killing of Staphylococcus epidermidis and Staph. hominis. All strains of Staph. epidermidis were rapidly killed in spite of the high MIC values (4-16 mg/l). The killing effect against Staph. haemolyticus was less rapid and marked than against Staph. epidermidis, with strain to strain variation. A 99.9% kill was achieved for most strains within 22 h, but with other isolates regrowth occurred which was due to the presence of highly resistant cells in the original population. Other staphylococci (Staph. aureus, Staph. saprophyticus) and Streptococcus pyogenes, Str. bovis and Str. salivarius were reduced by 99.9% within 22 h. Bactericidal activity against other streptococci (Str. mutans, Str. agalactiae, Str. faecalis, Str. faecium) was less marked; against Str. sanguis teicoplanin was bacteriostatic.