412. Host Response Biomarkers Predict Clinical Failure in Patients with Staphylococcus aureus Bacteremia (SAB) Treated with Flucloxacillin (FLU) or Vancomycin (VAN)

Abstract

BackgroundImbalance among innate mediators such as IL-1β, IL-10, and TNF-α portends poor outcomes of persistence and death in patients with SAB. Previous studies did not consider the role of antibiotic treatment in this important host–pathogen relationship. In this study of SAB, we determined cytokine signatures that correlate with the composite endpoint of clinical failure (bacteremia duration >4 days or 30-day mortality) in Australian patients treated with FLU or VAN.MethodsSera from 86 patients with SAB (24.4% MRSA) were obtained from a clinical study of patients treated with FLU or VAN. All of the patient samples were collected at clinical presentation (day 0 or day 1 of infection) and were treated with FLU or VAN throughout. Patients were classified into either clinical success (CS = 68) or clinical failure (CF = 18), defined as death or prolonged bacteremia >4 days. Patient demographic and infection characteristics were collected. A 10-multiplex TH1/TH2 cytokine analysis was performed using electrochemoluminescence with the Meso-Scale Discovery platform analyzed by Mann–Whitney U.ResultsPatients’ median values were significantly elevated and above the normal range in CF for IL-1β (P = 0.029), IL-10 (P = 0.018), TNF-α (P = 0.042), and IL-6 (P = 0.006) (figure). Epidural abscess source was associated with CF, but no other host or pathogen characteristics correlated to outcome. Patients infected with isolates with VAN MIC = 2 mg/L (by Etest and broth dilution) had lower concentrations of IL-1β and IL-10 (P = 1.5 mg/L. In ROC analysis, IL-1β, IL-10, TNF, and IL-6 were higher sensitivity and specificity predictors of CF (AUC 0.65–0.71; P = 0.05).ConclusionA suboptimal host immune response to SAB at presentation predicts adverse clinical outcomes. IL-10, TNF-α, and IL-6 serum concentrations appear to reflect immunopathology in patients with SAB. These predictive markers may be considered in therapeutic clinical decision-making, such as escalation of alternative therapies in high-risk patients and/or de-escalation treatment in low-risk patients. These data offer steps toward further refining therapeutic precision for patients with SAB beyond the standard clinical or microbiological metrics that are employed in current practice. Disclosures All authors: No reported disclosures.