Can a Good Gut Flora Turn Bad?

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Can a Good Gut Flora Turn Bad?

By NuBiome

For numerous bowel diseases such as Crohn’s and ulcerative colitis, some experts believe that the diseases may be caused by one or several “bad” bacteria.  The label “bad” generally means that they are looking for one or a few bacteria that are causing the inflammation.  In doing so they are following a known model of success, much like what was discovered by the Nobel Prize winners Robin Warren and Barry Marshall who discovered that stomach ulcers were not caused by an immune system that was out of control, but rather a previously unfamiliar and contagious bacteria called Helicobacter pylori that was causing bloody and painful ulcers in the stomachs of its victims.

But what if ulcerative colitis could be caused by normal bacteria that under certain conditions become, “colitic”, or collectively misbehave and attempt to invade or create noxious chemistries that under normal conditions, the same strains of bacteria would not produce?

In a landmark paper describing cutting edge research performed at the Harvard Medical School, published in Cell, researchers described an experiment where a set of mice had certain genes knocked out so that a specific molecule, called T-bet, was not produced in the group of test mice.  Those test mice, that had a slightly deficient immune system, developed gastrointestinal symptoms that resembled ulcerative colitis in humans.

A very important result was that even though no “bad” bacteria were introduced into the mice, somehow the mice developed a ulcerative colitis-like disease.  At this point would be easy to say that the disease was caused by the defective immune system was the cause of the disease, much like how stomach ulcers were once labeled a disease of an faulty immune system until Warren and Marshall came along.

Fortunately the Harvard researchers pushed the experiment a little further.  After the T-bet deficient mice started their colitis symptoms, they then introduced perfectly healthy mice, with intact immune systems, into the cages.  What happened next was surprising, the healthy mice ate the stool of the sick mice and contracted a milder form of the colitis.  This was the first documented case of a transmissible form of colitis that lacked a known “bad” bacteria.  The researchers suggested that an improper mixture of badly behaving, normal strains of bacteria, rather than bad strains, may be responsible for certain inflammatory bowel diseases.

Their discovery may help explain why certain probiotic strains can alleviate symptoms inflammatory bowel disease in certain people.  Besides killing off or competing for resources with the so called “bad” bacteria, the probiotics may be interacting and coaxing normal misbehaving strains of bacteria to behave more normally which temporarily reduces symptoms.