Risk factors for 28-day mortality in elderly patients with extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae bacteremia

Gram-negative bacteremia is common in elderly patients and, compared with younger patients, mortality rates in bacteremic elderly patients are high. ESBL-producing organisms were one of the most important risk factors associated with mortality. In addition, older age is one of risk factors for colonization or infection with ESBL-producing organisms. We conducted a retrospective cohort study to evaluate risk factors of all-cause 28-day mortality in elderly patients with ESBL-producing Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae) bacteremia. Patients aged 65 years or older, who had one or more blood cultures positive for E. coli and K. pneumoniae and who were hospitalized between January 2006 and December 2010 at a tertiary-care teaching hospital, were included. 191 bacteremic elderly patients were eligible for the study. The all-cause 28-day mortality rate was 24.6% (47/191). In multivariate analysis, prior antimicrobial therapy (p = 0.014) and an elevated SOFA score (p < 0.001) were independent risk factors for increased mortality, while urinary tract infection (UTI) was an independent determinant for non-mortality (p = 0.011). In the current study, prior antimicrobial therapy within 30 days, an elevated SOFA score and nonurinary source of infection were significantly associated with adverse outcomes in elderly patients with ESBL-producing gram-negative bacteremia.