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Volume 42, Number 3, June 2009

Clinical significance of and outcomes for Bacteroides fragilis bacteremia

Chun-Wen Cheng, Huang-Shen Lin, Jung-Jr Ye, Chien-Chang Yang, Ping-Cherng Chiang, Ting-Shu Wu, Ming-Hsun Lee
Division of Infectious Diseases, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan

Received: March 10, 2008    Revised: June 5, 2008    Accepted: July 7, 2008   


Corresponding author:

Dr. Ming-Hsun Lee, Division of Infectious Diseases, Department of Internal Medicine, Chang Gung Memorial Hospital, 5 Fu-Shin St, Gueishan 333, Taoyuan, Taiwan. E-mail: Dr. Ming-Hsun Lee This e-mail address is being protected from spam bots, you need JavaScript enabled to view it


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.




 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.



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).




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.


Key words:

Bacteremia; Bacteria, anaerobic; Bacteroides fragilis



J Microbiol Immunol Infect. 2009;42:243-250.