Infectious Toxins May Be Responsible for Inflammatory Bowel Diseases

Inflammatory bowel diseases (IBD) are serious conditions that affect the colon and small intestine as well as the mouth, esophagus, and stomach. These conditions can lead to vomiting, abdominal cramps and pain, weight loss, diarrhea, and even anemia.

According to the Crohn’s & Colitis Foundation of America, inflammatory bowel diseases – including ulcerative colitis and Crohn’s disease – may affect as many as 1.4 million people in the United States. These two diseases are also characterized by unprompted remissions and relapses.

Scientists from the University of California studied Bacteroides fragilis gene sequences in patients who had inflammatory bowel disease. The research was published in the April 2000 volume of the Emerging Infectious Diseases journal.

The researchers found the organism Bacteroides fragilis in 11 of the 83 patients with IBD. Out of the 57 patients with an active form of the disease, 19.3 percent displayed positive results for toxicity. None of the patients with an inactive form, however, were positive for toxicity of Bacteroides fragilis gene sequences.

This specimen is correlated with extraintestinal infections including soft tissue infections, diarrhea, and abscesses. While the organism is not associated with diarrheal infection in newborn infants, it takes hold in children between the ages of one to five years old.

Bacteroides fragilis is able to secrete an enterotoxin that is a zinc-containing metalloprotease with a molecular weight of 20,000. This substance causes intestinal problems. Some other microbial pathogens that may be responsible for IBD are Mycobacterium paratuberculosis, paramyxoviruses, E. coli and Listeria monocytogenes.

The Human Subjects Research Review Committee of the University of California approved the development of this study. After patients provided informed consent, samples were taken and analyzed. Out of the 83 subjects, 60 had Crohn’s disease and 23 had ulcerative colitis.

An active form of IBD was present in approximately 70 percent of the subjects. Additionally, 10 patients had irritable bowel syndrome while a control group of subjects had no history of diarrhea and no ulceration or erythema was found. Some of the typical procedures in this study included colonoscopy, endoscopy for collecting samples, and flexible sigmoidoscopy for evaluating abdominal cramps.

The specimens with B. fragilis were incubated anaerobically at 37°C for 48 hours and the enterotoxin was isolated in a colon cell line. A cytotoxicity assay was used and cells were allowed to attach to tissue culture plates and grow for two to three days.

The cultures were found to be positive for the enterotoxin when a visible cytopathic effect was nullified by a particular antiserum. As part of the trial, DNA was extracted from the specimens and primers were used to magnify the sequences.

This research further suggests the potential for toxins and infectious agents playing a role in IBD. Favorable clinical response of some patients to medications like antibiotics also show how these microorganisms could lead to the progression of inflammatory bowel diseases.

Additionally, pre-clinical studies have used animal models to show similar outcomes and causes of IBD. With more evidence of causes, better treatments for inflammatory bowel diseases are likely to be developed throughout the coming years.

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Categories: Inflammatory diseases

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