Impact of immunosuppressive agents on clinical manifestations and outcome of Staphylococcus aureus bloodstream infection - A propensity score matched analysis in two large, prospectively evaluated cohorts.

BACKGROUND Staphylococcus aureus bloodstream infection (SAB) is a common, life-threatening infection. The impact of immunosuppressive agents on the outcome of patients with SAB is incompletely understood. METHODS Data from two large prospective, international, multicenter cohort studies (INSTINCT and ISAC) between 2006 and 2015 were analyzed. Patients receiving immunosuppressive agents were identified and a 1:1 propensity score (PS) matched analysis was performed to adjust for baseline characteristics of patients. Overall survival and time to SAB-related late complications (SAB relapse, infective endocarditis, osteomyelitis, or other deep-seated manifestations) were analyzed by Cox regression and competing risk analyses, respectively. This approach was then repeated for specific immunosuppressive agents (corticosteroids [CSMT] and immunosuppressive agents other than steroids [IMOTS]). RESULTS Of 3,188 analyzed patients, 309 were receiving immunosuppressive treatment according to our definitions and were matched to 309 non-immunosuppressed patients. After PS matching, baseline characteristics were well balanced. In the Cox regression analysis, we observed no significant difference in survival between the two groups (death during follow-up: 105/309 (33.9 %) immunosuppressed patients vs. 94/309 (30.4 %) non-immunosuppressed, hazard ratio 1.20 (95% CI 0.84-1.71). Competing risk analysis showed a cause-specific hazard ratio (CSHR) of 1.81 (95% CI 0.85-3.87) for SAB-related late-complications in patients receiving immunosuppressive agents. CSHR was higher in patients taking IMOTS (3.69; 95% CI 1.41-9.68). CONCLUSIONS Immunosuppressive agents were not associated with an overall higher mortality. The risk for SAB-related late complications in patients receiving specific immunosuppressive agents such as IMOTs warrants further investigations.