Sounds like kind of a technical question.
In Irritable Bowl Disease, including Crohn’s Disease, it may be the case that bad bacteria cause intestinal wall inflammation. Or, inflammation could allow bad bacteria to do better than good bacteria. And, that might be an oversimplification because there could be other factors as well, including genetic predispositions.
Many younger people who present with various abdominal symptoms are treated with antibiotics. These antibiotics could disproportionately favor bad bacteria.
Whether from inflammation, genes, or use of antibiotics, it does seem that “dysbiosis” (having bad bacteria along with the good ones in your gut) is a problem.
The results of a large study are now being released that looks at this problem in a way that might untangle some of these questions. From Science (News):
The research, which involved 668 children, shows that numbers of some beneficial bacteria in the gut decrease in Crohn’s patients, while the number of potentially harmful bacteria increases. The study could lead to new, less invasive diagnostic tests; it also shows that antibiotics—which aren’t recommended for Crohn’s but are often given when patients first present with symptoms—may actually make the disease worse.
Some potentially harmful microbial species were more abundant in Crohn’s patients, such as those belonging to the Enterobacteriaceae, Pasteurellaceae, Veillonellaceae, and Fusobacteriaceae; numbers of the Erysipelotrichales, Bacteroidales, and Clostridiales, generally considered to be beneficial, were lower. The disappearance and appearance of species can be equally important, says Dirk Gevers of the Broad Institute in Cambridge, Massachusetts, who performed most of the work. “There has been a shift in the ecosystem, which affects both types.”
The subjects tended to not have been treated with antibiotics, or at least, not much (yet), but there was variation and those who had received more antibiotic treatments seemed to have more dysbiosis.
The dysbiosis was also more pronounced in patients who had received antibiotics. “This study confirms that these drugs don’t do any good to people with Crohn’s disease,” says gastroenterologist Séverine Vermeire of the Catholic University of Leuven in Belgium, who was not involved in the study. “We knew antibiotic use increases the risk to develop the disease; now we know they can worsen it, too.”
The main outcome of this research may be the development of easier to implement and more reliable diagnostic techniques. But it also seems to advance understanding of Crohn’s. What this study does not do directly, though, is address the strange epidemiological signal whereby Crohn’s seems to be increasing in western populations. Something we are doing may be involved. Most people seem to assume this is dietary, but I won’t bet a dime on that. This could have to do with all sorts of other practices that ultimately influence gut flora, from hand washing and diapering practices to food related but not strictly dietary choice related changes, such as how bacteria is removed from food during processing.
Vermeire says it’s a “missed opportunity” that the researchers didn’t look at the patients’ diets. “That could have helped elucidate why this disease occurs so much more in the Western world than elsewhere.” In 2011, Vermeire’s group published a study showing that healthy family members of Crohn’s disease patients have a slight dysbiosis as well. Vermeire is convinced that even in these families, it’s not genetics but some lifestyle factor that causes the phenomenon. “If we could identify the dysbiosis in an early stage, and we knew the causative factors,” she says, “we could prevent disease occurrence by bringing about lifestyle changes.”