Risk factors for mortality in Elizabethkingia spp. bloodstream infections

Elizabethkingia spp. are uniquely challenging nosocomial pathogens to manage. Clinical breakpoints are not defined for trimethoprim-sulfamethoxazole (TMP-SMX), levofloxacin or piperacillin-tazobactam. We describe the clinical, laboratory and microbiological parameters that are associated with increased mortality in patients with Elizabethkingia spp. bacteraemia.

We retrospectively examined consecutive patients with Elizabethkingia spp. bacteraemia from 2012 to 2024, comparing those who experienced in-hospital mortality and those who survived. Additionally, in the subgroups of patients receiving piperacillin-tazobactam, levofloxacin or TMP-SMX for therapy, we investigated if the antimicrobial susceptibility testing minimum inhibitory concentrations (MICs) correlated with adverse outcomes.

We identified 127 distinct episodes of Elizabethkingia spp. bacteraemia. In-hospital mortality was 29.9% (n = 38). Prolonged duration of fever, elevated C-reactive protein, total white cell count and lactate dehydrogenase levels were associated with mortality. Most patients who survived received a duration of antibiotics 2 weeks or longer (84.3% vs. 21.6%, P < 0.001). On multivariable analyses, a prolonged duration of fever and elevated C-reactive protein remained independently associated with mortality, after adjusting for age, Pitt bacteraemia score, antibiotic regimen and interventions for source control such as line removal. No specific antimicrobial regimen was independently associated with improved survival. Elevated levofloxacin MICs were associated with adverse outcomes in patients empirically treated with levofloxacin. Similar trends were not observed with piperacillin-tazobactam or TMP-SMX.

Prolonged fevers and elevated C-reactive protein predicted mortality in Elizabethkingia spp. bacteraemia. Levofloxacin but not piperacillin-tazobactam or TMP-SMX MICs appear to correlate with outcomes. Future larger prospective studies would help define clinical breakpoints.