The role of vancomycin in the persistence or recurrence of Staphylococcus aureus bacteraemia

Persistence and recurrence of Staphylococcus aureus bacteraemia (SAB) have been linked primarily with difficult-to-eradicate foci of infection such as endocarditis, osteomyelitis or abscess formation. Although vancomycin therapy has been suggested as a predictor of relapse of SAB, it has never been shown to be associated with persistent SAB. The purpose of this study was to examine the possible association of vancomycin therapy and persistence of SAB. Two groups of patients were retrospectively studied. One group consisted of 124 patients who completed > or =10 d of appropriate anti-staphylococcal therapy (from among a total of 284 patients with SAB during 2 y, 1997-8). In this group, persistence of SAB (methicillin resistant and susceptible combined) for >3 d while on therapy, occurred in 11 (22%) of 55 vancomycin recipients and in none of 52 cloxacillin recipients (p = 0.002). When calculated for methicillin susceptible SAB alone, the numbers were 3 of 13 vs 0 of 52, respectively (p = 0.007). The second study group included all patients with persistence and/or relapse of SAB while on appropriate anti-staphylococcal therapy during 4 y (1997-2000). In this group, the persistence occurred while on vancomycin therapy, in 32 (94%) of 34 patients with >3 d of persistence of SAB. In the majority of these patients a secondary focus of infection serving as the site of persistence was identified in addition to the primary focus (or portal of entry). It was concluded that vancomycin is inferior to cloxacillin therapy in terminating SAB and therefore may predispose to prolonged bacteraemia and secondary seeding of infection during therapy.