The post-antibiotic effect of teicoplanin: monotherapy and combination studies

The post-antibiotic effect (PAE) of teicoplanin was measured alone and in combination with other antibiotics against Staphylococcus aureus. A total of five strains were used: the Oxford S. aureus and two clinical isolates each of methicillin sensitive and methicillin resistant strains. Fusidic acid had no or a small post-antibiotic influence (range 0-1.25 h) whereas a relatively higher PAE was seen for all other drugs against all strains: teicoplanin 2.4-4.1 h: gentamicin 3.1-5.2 h, rifampicin 3.0-3.95 h, and ciprofloxacin 1.6-3.4 h. Combination of teicoplanin with fusidic acid resulted in shorter PAEs than teicoplanin alone. In contrast, PAEs for all other combinations with teicoplanin were longer than PAE of teicoplanin, gentamicin, rifampicin or ciprofloxacin alone. Addition of teicoplanin during the post-antibiotic phase of the other antibiotics and vice versa showed that the only combination which was consistently bactericidal was that of teicoplanin with gentamicin. We conclude that these in-vitro results suggest that the combination of teicoplanin with gentamicin is likely to be the most effective of those tested and should be further evaluated in clinical trials.