Bacteremia caused by non-sporulating anaerobes in cancer patients. A 12-year experience.

The clinical, epidemiological and laboratory characteristics of bacteremia caused by anaerobic organisms other than Clostridium spp. in cancer patients are described and compared to other previously reported series. Of the 315 episodes, 246 (78%) were caused by a single organism and 69 (22%) were polymicrobial. The most common underlying malignancies were genitourinary and gynecological tumors, acute leukemia, and gastrointestinal malignancies. Most patients (94%) were febrile, and septic shock was documented in 24% of monomicrobial episodes and in 58% of those with polymicrobial infection. Soft-tissue infection was present in 44% of the cases, and it presented as tissue necrosis in 11%. The most common sites identified as the portal of entry were intra-abdominal abscesses, soft tissue, and the oropharynx. The most common organisms were Bacteroides fragilis (57%) and other Bacteroides spp. (22%). Most polymicrobial infections were caused by 2 organisms, the second most commonly another anaerobe or an aerobic gram-negative bacillus. The most active antibiotic in vitro was chloramphenicol. High rates of resistance to penicillin were observed not only among B. fragilis, but also among Bacteroides spp. The frequency of penicillin resistance increased throughout the study years. The overall survival was 70%. The cure rate for monomicrobial bacteremias was 76% vs. 51% for polymicrobial episodes. Infection was the cause of death in 20 and 16 episodes, respectively. The response rate for patients in septic shock was 47% in contrast to an 85% recovery rate for those without it. Ninety-five patients had documented abscesses accompanying the bacteremic episode. The most effective antibiotics were clindamycin and chloramphenicol. Overall response to penicillin was only 13%. Suboptimal responses were also observed for the antipseudomonal penicillins. High response rates (82%) were also obtained with cefoxitin, metronidazole, and moxalactam.