Clinical significance of and outcomes for Bacteroides fragilis bacteremia

Abstract

Background and purpose: Bacteroides fragilis is a virulent anaerobic pathogen, resulting in considerable mortality. This study was conducted to investigate the clinical characteristics, significance of polymicrobial bacteremia, and treatment outcomes of B. fragilis bacteremia.

Methods: This retrospective analysis enrolled 199 adult patients with B. fragilis bacteremia, who were admitted to hospital between January 2004 and May 2007. Chi-squared and Fisher's exact tests were used for comparison. A p value of <0.05 was considered statistically significant.

Results: 142 patients with B. fragilis bacteremia (71.4%) had at least 1 underlying disease. Malignancy was the commonest comorbidity (n = 62; 31.2%). Intra-abdominal infection accounted for 49.3% of the infection sources. Seventy seven patients (38.7%) had polymicrobial bacteremia and Escherichia coli was the most common concurrent isolate (n = 24). There was no significant difference in septic shock incidence and clinical outcome between the monomicrobial and polymicrobial groups. The overall 30-day crude mortality rate was 30.7%. Inappropriate early antimicrobial therapy did not affect outcome, but a higher mortality rate was noted for patients who never received appropriate antimicrobial therapy (55.2% vs 26.5%; p = 0.002). Independent risk factors for mortality were age 65 years and older (p = 0.010), malignancy (p = 0.001), shock (p < 0.001), thrombocytopenia (p = 0.026), and lack of surgical intervention (p = 0.035).

Conclusions: B. fragilis bacteremia causes a high mortality rate, especially for elderly people and patients with cancer. Clinicians should be alert to the infectious focus, and appropriate surgical intervention may be necessary to improve outcomes.