The prophylactic and therapeutic activities of teicoplanin were evaluated in two different experimental models of foreign body infections caused by methicillin-resistant Staphylococcus aureus (MRSA). In a guinea pig model of prophylaxis, subcutaneously implanted tissue cages were infected at a >90%6 rate by 102 Bacterial infections of prosthetic devices are a major cause of morbidity and implant failure. Antimicrobial therapy of foreign body infections caused by Staphylococcus aureus is notoriously difficult, and microbial eradication frequently requires the removal of infected materials. An additional serious problem for the therapy of foreign body infections is the increasing incidence of methicillin-resistant strains of S. aureus (MRSA) that frequently express a large number of additional determinants for resistance to several major categories of antistaphylococcal agents. Although vancomycin is the reference antibiotic for treating MRSA infections, its activity against deep-seated infections is not always optimal (30, 32) and frequently requires the parallel administration of other antimicrobial agents such as aminoglycosides or rifampin (18, 49).There are three major concerns about increasing the use of vancomycin. The first one is its narrow toxic to therapeutic ratio involving serious toxic side effects; the second one is the exclusive intravenous route for administration of this agent, thus involving extensive hospital stay and costs; the third one is the growing concern about the possible acquisition of vanco-* Corresponding author. Teicoplanin is a glycopeptide antibiotic with an antibacterial spectrum similar to that of vancomycin (24), but with a much longer half-life and less serious side effects (16,23,43,52). Unlike vancomycin, teicoplanin is well tolerated after intramuscular administration, and its prolonged half-life is suitable for once-daily dosing (43). Several clinical or experimental studies evaluated the efficacy of teicoplanin for treating deepseated staphylococcal infections. Taken together, these different studies have led to discrepant results and controversial interpretations concerning teicoplanin safety and efficacy (see reviews in references 8, 15, and 16). The divergent results of these clinical studies may be explained by significant differences in their design, for example, the choice of open (4, 22, 23, 31, 33, 36, 47) versus comparative (7, 17, 20, 46, 48, 50) trials, and by the wide range of dosage regimens, treatment durations, and antibiotic combinations used by the different investigators.The major objective of our experimental study was to evaluate the efficacy of teicoplanin in two related animal models of foreign body infections caused by an MRSA strain (12, 34). The first of these models (5) was more suitable for assessing the prophylactic activity of teicoplanin on MRSA challenge, whereas the second one (34) evaluated its activity for the treatment of chronic subcutaneous implant-related infections caused by MRSA. In both animal models, teicoplanin was administer...