Clinical and microbiological characteristics of persistent Staphylococcus aureus bacteremia and risk factors for mortality: CD4 + T cells play an important role

Objectives: This study evaluated the risk factors for mortality and the T cell immune response in patients with persistent Staphylococcus aureus bacteremia (SAB). Methods We studied a prospective cohort of adults with SAB at a tertiary-care hospital in South Korea from 2008 to 2020. We compared the clinical and microbiological characteristics of patients with persistent bacteremia (PB). The concentrations of cytokines and the proportions of IFN-γ secreting CD4 + T cells were measured serially during the bacteremia period. Results Of the 1,760 patients, 242 had PB, and 49 PB patients died within 30 days. In the multivariate analysis, the APACHE II score, liver cirrhosis, and female sex were independently associated with 30-day mortality. The level of IL-10 was significantly increased in the plasma of patients with a high Pitt bacteremia score and those who died within 12 weeks from the index day. The proportion of IFN-γ-secreting CD4 + T cells were the highest just before the positive-to-negative conversion of blood cultures in patients with a low Pitt bacteremia score and those who survived for 12 weeks. Conclusions The level of IL-10 is correlated with clinical outcomes in PB patients. IFN-γ secreting CD4 + T cells might play a pivotal role in SAB PB.