We present an intriguing case report of a septicemic post-elective surgical staphylococcal knee
arthritis and
cellulitis which did not respond to long-term courses of associated
rifampicin and
teicoplanin or
vancomycin despite apparently favourable in vitro susceptibility assays, but rapidly resolved after i.v. followed by
oral administration of
linezolid. The lack of response to a two-week course of
glycopeptides cannot be explained by the in vitro mimimum inhibitory concentrations (MIC90) of involved organisms, which showed full susceptibility of Staphylococcus aureus to
vancomycin and
teicoplanin, and sensitivity of an accompanying Staphylococcus epidermidis isolated from blood cultures to
vancomycin and
rifampicin, with borderline "intermediate" values found for
teicoplanin. Since neither
abscess formation nor bone involvement were of concern, effective
glycopeptide and
rifampicin penetration into infectious tissue should have been ensured. From a clinical point of view, only the introduction of a two-week i.v.
linezolid followed by one more week of oral
linezolid obtained a complete clinical and microbiological cure, and an unhoped-for functional success. When managing severe multiresistant gram-positive
infections, in vitro activity should be carefully evaluated against expected
drug penetration rates into the relevant infectious tissues.