Community-acquired culture-negative endocarditis: clinical characteristics and risk factors for mortality.

Objectives: We studied the clinical characteristics, in-hospital mortality, and long-term prognosis of patients with culture-negative endocarditis.

Methods: In total, 221 episodes of definite endocarditis were studied (2004-2009). We compared the clinical, laboratory, and echocardiography characteristics and the survival rates of patients with culture-negative and culture-positive endocarditis. Survival after hospital discharge was evaluated using the Kaplan-Meier method and coefficient of mortality comparisons.

Results: Culture-negative endocarditis occurred in 51/221 (23.1%) episodes. Compared with the culture-positive endocarditis patients, the time elapsed between admission and initiation of antibiotic therapy was longer in patients with culture-negative endocarditis (p<0.001), and these patients also had lower C-reactive protein levels at admission (p<0.001). In-hospital mortality rates were not different between culture-negative and culture-positive patients. After hospital discharge, there was also no significant difference between groups in survival curves (p=0.471). Severe sepsis (adjusted prevalence ratio 3.32, p=0.010) and diabetes mellitus (adjusted prevalence ratio 2.32, p=0.009) were independently associated with in-hospital death in culture-negative patients.

Conclusions: Culture-negative endocarditis patients presented with lower levels of C-reactive protein at admission and required more time for initiation of antibiotic therapy, although there was no difference in in-hospital mortality or long-term survival between culture-negative and culture-positive endocarditis patients. Diabetes mellitus and severe sepsis were associated with in-hospital death in patients with culture-negative endocarditis.