Clinical Characteristics and Risk Factors for Mortality due to Bloodstream Infection of Unknown Origin in Hemodialysis Patients: A Single-Center, Retrospective Study

INTRODUCTION Hemodialysis patients are at a high risk of bloodstream infection (BSI). The risk factors for BSI-associated mortality, especially of unknown origin, remain uncertain. BSI of unknown origin is highly prevalent and related to high mortality. The present study aimed to investigate the clinical and microbiological characteristics of BSI and risk factors for BSI-associated mortality, including BSI of unknown origin, in hemodialysis patients. METHODS This study was a single-center, retrospective study conducted from August 2012 to July 2019 in hemodialysis patients with BSI at Kawashima Hospital. Data related to demographics, clinical parameters, BSI sources, causative microorganisms, and initial treatments were collected from the medical records. The predictors for mortality associated with BSI were evaluated by logistic regression. RESULTS Among 174 patients, 55 (30.9%) had the infection from unknown origin. The most frequent bacterium was Staphylococcus aureus. Low serum albumin level was an independent predictor of mortality due to BSI (odds ratio [OR]: 0.28, 95% confidence interval [CI]: 0.13-0.59). A lower serum albumin level (≤2.5 g/dL) was associated with poorer mortality. Methicillin-resistant Staphylococcus aureus (MRSA) was independently associated with mortality due to BSI of unknown origin (OR: 6.20, 95% CI: 1.04-37.1); 87.5% cases with BSI of unknown origin due to MRSA were not initially administrated anti-MRSA antibiotics, and in such patients, the mortality rate was 85.7%. CONCLUSIONS Serum albumin level of 2.5 g/dL is a cutoff value, which could predict the mortality due to BSI in hemodialysis patients. Considering the high mortality rate of MRSA-associated BSI of unknown origin, wherein no focus of infection was identified in the present study, initial empiric treatment should be considered for MRSA-associated BSI of unknown origin.