Dynamics of monocytic HLA-DR expression differs between bacterial etiologies during the course of bloodstream infection

OBJECTIVE In the pathogenesis of sepsis, activation of both pro- and anti-inflammatory responses are key components, but knowledge is lacking on the association between bacterial etiology and development of dysregulated responses with sustained immunosuppression. The aim of this study was to evaluate how the immunosupression marker HLA-DR on monocytes (mHLA-DR) is associated with bacterial etiology and markers of inflammation during the clinical trajectory of bloodstream infection (BSI). METHODS Ninety-one adults, predominantly non-ICU patients, with BSI caused by Streptococcus pneumoniae (n = 27), Staphylococcus aureus (n = 22), Escherichia coli/Klebsiella pneumoniae (n = 23), and other species (n = 19) were prospectively included, and sampled on admission (day 0) and on days 1-2, 3, 7±1, 14±2, and 28±4. RESULTS The dynamics of mHLA-DR, measured by flow cytometry, differed significantly between etiology groups (p