Infections caused by anaerobic bacteria are common, and may be serious and life-threatening. Anaerobes predominant in the bacterial flora of normal human skin and mucous membranes, and are a common cause of bacterial infections of endogenous origin. Infections due to anaerobes can evolve all body systems and sites. The predominate ones include: abdominal, pelvic, respiratory, and skin and soft tissues infections. Because of their fastidious nature, they are difficult to isolate and are often overlooked. Failure to direct therapy against these organisms often leads to clinical failures. Their isolation requires appropriate methods of collection, transportation and cultivation of specimens. Treatment of anaerobic bacterial infection is complicated by the slow growth of these organisms, which makes diagnosis in the laboratory only possible after several days, by their often polymicrobial nature and by the growing resistance of anaerobic bacteria to antimicrobial agents.

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Tuesday, October 18, 2011

A Link Between Fusobacterium species and Colon Cancer


The possibility that are associated of Fusobacterium species with colonic cancer was suggested in two studies published in Genome Research. The organism was detected in colon cancer cells by both Meyerson et al from the Dana Farber Cancer Institute and Holt et al from the British Columbia Cancer Agency Genome Sciences Center. The two research groups used genetic probes to identify the bacteria found in the tumor tissues.  

Fusobacterium species are mostly found in the mouth and are linked to periodontal disease and oral infections. It is rarely found among the usual gastrointestinal bacteria, but it appears to the only type of bacteria inside colonic cancer cells.  


Gram staining of Fusobacterium nucleatum 



Meyerson et al looked for bacterial DNA, comparing tumor tissue and healthy colon samples from nine patients with colonic cancer. They found Fusobacteria DNA mostly in the cancer tissue. In further studies these investigators found Fusobacterium species in 95 other colon cancer patients.  

Holt et al. focused on RNA instead of DNA. These investigators studied colon cancer biopsies and normal tissues of 11 patients and found that Fusobacteria were more likely to be in cancer tissue than in normal cells. In some specimens, the number of Fusobacteria was hundreds of time higher in cancer cells than in normal tissues.   The investigators also found that other types of bacteria that commonly reside in the gut are depleted in colon cancer tissues. Whether the Fusobacteria are crowding out these more common bugs, or whether they tend to die off in the presence of malignant cells isn't known.  

Currently it is unclear whether or how Fusobacteria might be contributing to the development of cancer. These organisms may promote inflammation, which can contribute to malignant transformation in normal cells. Alternatively, the tumor environment may be more hospitable to Fusobacterial growth, and the high number of this bacterium would be a consequence, not the cause, of the cancer.



Colonic cancer