[Anaerobic bloodstream infections: study of 68 episodes]

There is some controversy regarding the current rates of anaerobic bacteremia. Some authors have described an increasing incidence in recent years, whereas others report declining rates. There is even debate over whether to routinely perform anaerobic blood cultures. We present a prospective analysis of anaerobic bloodstream infections diagnosed at our medical center from January 2003 to May 2008.

Sixty-eight patients had bloodstream infection caused exclusively by anaerobic bacteria. Median age was 64+/-19 years and 63.2% had at least one comorbid condition, including 20.6% with a solid neoplasm, often related to the gastrointestinal tract. The main focus of anaerobic bacteremia was the abdomen (42.6%). The most common isolates were several species from the Bacteroides fragilis group (36.7%), Clostridium spp. (17.6%), Peptostreptococcus spp. (16.1%), and Prevotella spp. (16.1%). Empirical antimicrobial treatment was adequate in 69.1%. Overall mortality was 23.5%, and bacteremia-related mortality was 9.2%. Sepsis, septic shock, and a Pitt score >4 were independent predictors of mortality.

The incidence of anaerobic bacteremia in our hospital was 0.89 cases per 1000 hospital admissions. Patients at high risk were elderly persons with associated underlying diseases including malignant disease. Mortality was high.