Anaerobic Bacteremia Rare But Morbid in Cancer Patients
Abstract & Commentary
By Joseph F. John, MD, Chief, Medical Subspecialty Services, Ralph H. Johnson Veterans Administration Medical Center, Professor of Medicine, Medical University of South Carolina, Charleston, SC, is Associate Editor for Infectious Disease Alert
Dr. John does research for Merck, is a consultant for Cubist, Roche, and bioMerieux, and is on the speaker’s bureau for Pharmacia, GSK, Merck, Bayer, and Wyeth.
Synopsis: The mortality rate for patients with adequate antimicrobial therapy from the outset was 14%, compared with 63% for patients who were not treated adequately at any time.
Source: Zahar JR, et al. Incidence and Clinical Significance of Anaerobic Bacteremia in Cancer Patients: A 6-Year Retrospective Study. Clin Microbiol Infect. 2005;11:724-729.
The Gustave-Roussy Institute is a 400-bed hospital near Paris, that serves patients with solid and hematological malignancies. This study of anaerobic bacteremia covered the period from 1993-1998. There were 7989 positive blood cultures (6.8%) that were considered significant. Only 0.6% of all blood cultures, however, grew anaerobic bacteria. Forty-five patients were considered to have significant anaerobic bacteremia, 13 with hematological disease and 32 with solid tumors. Chemotherapy had not been successful in 44 of these patients, and 14 had a recent history of metastatic disease.
Pathogens most often recovered included Bacteroides fragilis (31%), and Gram-positive anaerobes (31%), usually Clostridium perfringens (16%). The G-I tract was the most common source in 49%, followed by oral mucositis (16%). Infection was usually the reason for admission. Various antimicrobials were used, but death was significantly associated with immediate inadequate antimicrobial therapy, as judged by Zahar and colleagues. Only 13 patients (29%) were considered to have received adequate therapy. Regarding antimicrobial susceptibility, all pathogens showed susceptibility (employing French guidelines) to aminopenicillins with or without beta-lactamase inhibitors, carbepenems, and metronidazole.
Mortality was 42% overall and was higher (63%) in those patients who did not receive adequate antimicrobial chemotherapy. In contrast, only 14% of patients who received adequate antibiotic therapy died. The median time between the positive blood culture and death was 4.5 days (range, 3-16 days).
Commentary
This study shows that at specialized hospitals for the care of cancer patients, anaerobic bacteremia is rare even when bacteremia is detected in nearly 7% of blood cultures. Clinicians already know that poor outcomes in infected, seriously ill patients are associated with inappropriate antimicrobial therapy. Unfortunately, empiric antimicrobials may not include agents active against pathogens that cause anaerobic bacteremia. Even though anaerobic bacteremia in cancer patients is rare, its outcome if often fatal. In this study, anaerobic bacteremia was associated with GI and hematological malignancies. So when clinicians suspect bacteremia in these 2 groups of patients, antimicrobial agents active against anaerobes should be included in the empiric regimen.
Zahar et al also note the high rate of patients in their study with chemotherapy-induced mucositis. Neutropenia combined with oral mucositis may predispose to anaerobic bacteremia and should prompt good anaerobic antimicrobial coverage.
This study is one of the few that analyzed strict anaerobes recovered in blood cultures. Like many phenomena in infectious diseases, the incidence is low but the outcomes may prove fatal if the antibiotic regimen does not inhibit the infecting agent. Because of the high rate of mortality seen in this study, it can be argued that clinical laboratories should continue to isolate anaerobic bacteria from blood cultures, and clinicians should use susceptibility patterns to choose optimal antimicrobial agents.
The Gustave-Roussy Institute is a 400-bed hospital near Paris, that serves patients with solid and hematological malignancies. This study of anaerobic bacteremia covered the period from 1993-1998. There were 7989 positive blood cultures (6.8%) that were considered significant.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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