ABSTRACT
Anaerobic bacteremia has been most frequently related to an abdominal infection source
(50-70% of cases), pelvic infections (5-20% of cases), and skin and soft tissue infections (5-20%
of cases). Anaerobes accounted for 10% to 20% of episodes of bacteremia in studies performed
up to the 1990s (1). However, in the 1990s the incidence was lowered to approximately 4%
(0.5-12%) of all cases of bacteremias (or approximately one case per 1000 admissions), with
variation by geographic location, hospital patient demographics, and especially patient age
(2). Increased awareness of the importance of anaerobes and enhanced recognition of the types
of clinical infection caused by these organisms, along with appropriate prophylaxis and
treatment, were postulated as reasons that explain the decrease in the incidence of anaerobic
bacteremia during 1974-1988 (2). Recent studies, however, documented a resurgence in
bacteremia due to anaerobic bacteria. A study from the Mayo Clinic (Rochester, Minnesota,
U.S.A.) has reported that the mean incidence of anaerobic bacteremias increased from 53 cases
per year during 1993-1996 to 75 cases per year during 1997-2000 to 91 cases per year during
2001-2004 (an overall increase of 74%). The total number of cases of anaerobic bacteremia per
100,000 patient-days increased by 74% (p! 0.001). The number of anaerobic blood cultures per
1000 cultures performed increased by 30% (pZ0.002) (3).
