The Clinical Significance of Bacteroides Fragilis Bacteremia in Gastrointestinal Diseases

Background: Infections due to anaerobic pathogens are rare in clinical practice but carry a high mortality rate. This study aimed to explore the clinical manifestations of patients with Bacteroides fragilis (B. fragilis) bacteremia. Methods: We retrospectively studied patients with B. fragilis bacteremia from January 2003 to December 2008 in a teaching hospital in Northern Taiwan. Patients with positive blood culture due to B. fragilis were collected. We investigated the clinical manifestations, underlying diseases, risk factors of mortality, association with gastrointestinal tumors, and outcomes. Results: We identified 49 patients with B. fragilis bacteremia out of 61235 positive blood culture sets in 6 years. The overall incidence of B. fragilis bacteremia was 0.08% per year. The average age was 72 ± 1.6 years (range: 45-90 years). Of the 49 patients, 14 patients demised, yielding an overall mortality of 29%. The main portals of bacterial entry were the gastrointestinal and hepatobiliary tracts (33/49, 67%). The most common underlying gastrointestinal disease associated with B. fragilis bacteremia was the 9 gastrointestinal tumors, which were all malignant. The main predisposing risk factors included soft tissue infection, biliary tract infection, and gastrointestinal organ perforation. Fatality correlated with the presence of ascites (9.7% in the survivors group vs. 50% in the demised group, p = 0.005) and anemia (45.2% in the survivors group vs. 78.6% in the demised group, P = 0.037). Conclusions: B. fragilis bacteremia has a high mortality rate, and B. fragilis often gets access from gastrointestinal lesions, e.g. gastrointestinal tumors. When B. fragilis bacteremia is detected clinically, it warrants investigation for possible gastrointestinal malignancies.