Cannula-associated Staphylococcus aureus bacteraemia: outcome in relation to treatment

Despite the frequency of cannula-associated Staphylococcus aureus bacteraemia (CASAB) there is uncertainty regarding the duration of treatment required.

To determine the relationship between the duration and type of treatment for CASAB and subsequent relapse with deep-seated S. aureus infection.

We prospectively studied 276 patients with CASAB. Patients were followed for at least 8 weeks after completion of antibiotic treatment. Initial and subsequent isolates of S. aureus were compared using molecular methods to determine strain similarity.

Initial mortality was 9% (26 of 276) and a complicating focus of infection presented during initial treatment in 6% (15 of 250) of the survivors. There were nine relapses of deep-seated infection from the strain causing the original infection. Relapses were equally common following peripheral CASAB and central CASAB. There was no relationship between the duration of treatment and the rate of relapse of deep-seated infection (P = 0.24). This observation held true regardless of whether the duration of treatment was analysed as < or = 7 versus > or = 8, < or =10 versus > or =11, or < or=14 versus > or =15 days (P = 0.62, 0.87 and 0.16, respectively).

Episodes of peripheral CASAB pose an equal risk of relapse to central cannula-related episodes. Although further studies are needed to determine the optimal treatment of CASAB, our study strongly suggests that more than 14 days treatment is excessive for most patients who respond promptly to cannula removal and antibiotic treatment.