Gut Bacteria and Crohn’s Disease - An Overview

Introduction

A chronic inflammatory condition that involves any part of the gastrointestinal tract, from the mouth to the anus, is called Crohn’s disease. The incidence of this condition is increasing, which can be a concern globally. The cause of this condition is still unknown. It is multifactorial and also depends on host genetics and environmental factors. The immune response to this causes inflammation in the intestine.

What Is Crohn’s Disease?

An inflammatory condition that causes irritation and resultant inflammation in the bowels is called Crohn’s disease. It is a type of gastrointestinal condition called inflammatory bowel disease (IBD). It is thought to be an auto-immune condition, where the body’s immune system mistakenly tries to destroy healthy cells. The common symptoms include abdominal pain, diarrhea, weight loss, and rectal bleeding. There is no cure for the condition. However, it can be managed to lead an active life.

What Is Gut Bacteria?

The human body hosts many millions of bacteria. Some of them live in the gastrointestinal tract and comprise the gut microbiome. They live in imbalance with each other in a healthy individual. However, in conditions like Crohn’s disease, the balance is disrupted, making it prone to diseases.

What Are the Functions of Gut Bacteria?

The gut microbiome has many functions, which include:

• Breaking down food substances that otherwise remain as toxic substances.

• Influence the immune system.

• Prevent the harmful bacteria from overgrowing.

• Making vitamins and minerals like vitamin B and vitamin K.

• Digestion of complex carbohydrates like starch and fiber.

When the body breaks down complex carbohydrates like fiber and starch, short-chain fatty acids are produced. Experts believe that these short-chain fatty acids are beneficial to maintaining health and preventing diseases like Crohn’s disease.

How Does the Gut Microbiome Alter in Crohn’s Disease?

The gut microbiome and the immune system are closely linked. This has an impact on the gastrointestinal system in Crohn’s disease. The advancements in technology, like new molecular techniques and bioinformatics tools, have helped to understand the alterations in the gastrointestinal tract and how it affects the gut in Crohn’s disease. Many studies have shown a close link between gut dysbiosis and certain characteristics like inflammation, intestinal permeability, and postoperative recurrence. In addition, research has established that these patients have decreased bacterial diversity and altered taxonomic abundance, like a decrease in micro-organisms that promote health and an increase in pathogenic micro-organisms like Escherichia, Fusobacterium, and Mycobacterium species. This dysbiosis can be a factor that causes the development of such chronic intestinal inflammatory conditions. However, the exact micro-organism and host interactions and their pathophysiology are not yet fully understood.

How Is Intestinal Inflammation and Gut Dysbiosis Linked to Crohn’s Disease?

Different factors, like genetics and environmental factors like pollution, diet, and lifestyle, modify an individual’s susceptibility to Crohn’s disease. These non-genetic factors also influence intestinal permeability (the ability of the intestinal epithelium to pass through molecules depending on its concentration gradient) and, in turn, the gut microbiome. The gut microbiome, in turn, responds to the body’s immune system to maintain physiological homeostasis (a state of balance where all the systems in the body function correctly for survival). Hence, a disturbance in the normal microbiome can cause the immune system to have exacerbated responses and altered cytokine (a type of protein in the immune system that is important for cell signaling) production, which can worsen the condition.

Studies show that a reduction in the microorganisms with anti-inflammatory properties and an increase in the ones with pro-inflammatory capacities is the reason for gut dysbiosis in patients with IBD. This, in turn, favors the augmented and disturbed pro-inflammatory cytokine production. The change in microbial flora can cause a reduction in the nutrients absorbed, elevated levels of water or blood in the intestines, and an increased frequency of urgent bowel movements, which are the characteristic features of the condition.

People with Crohn’s disease also have elevated levels of a gram-negative bacteria called Klebsiella pneumoniae. This is usually abundant in their oral cavity. Despite being an anaerobic bacteria (bacteria that can survive without oxygen), it can survive in areas with a restricted oxygen supply. In Crohn’s disease, the oxygen level in the intestine is higher than normal. As a result, Klebsiella has the upper hand in survival when compared to the other anaerobic bacteria. This can worsen the condition by increasing the inflammation.

What Can Be Done to Promote Good Gut Bacteria in Crohn’s Disease?

Research is ongoing as to what exactly can be done to treat or manage Crohn’s disease intestine. Since dysbiosis plays an important role in the condition, altering the composition of the microbiome might help in managing it. A wide range of treatment options are under research for this. Some are widely practiced, while others are still under clinical trials.

• Antibiotics: A class of drugs that are used to kill a group of bacteria are called antibiotics. They are usually prescribed after a patient undergoes surgery for Crohn’s disease to prevent infections or further complications like abscesses. Some studies show a reduction in the symptoms when a patient with Crohn’s disease is put on antibiotics. However, more research showed that antibiotics probably have only moderate benefits when treating active Crohn's disease. This requires more research to be authenticated. However, another aspect of this is that antibiotics not only destroy the harmful bacteria but also negatively impact the beneficial microbes. The antibiotic resistance of the micro-organisms is yet another undesired impact.

• Probiotics: Live bacteria and other microorganisms that are beneficial to health are called probiotics. They are available in some types of food, like curd and other fermented foods. In addition, they are also available as dietary supplements. While some studies state that probiotics are beneficial in managing Crohn’s disease intestines, others argue that they are not. More research is required to finalize the results. However, patients have noticed moderate relief from their symptoms after using probiotics.

• Diet Modifications: Modifying diet can help manage the condition to some extent. Certain diets promote healthy bacteria, while others destroy them. Individuals should analyze their diet to see what food helps them feel better and what exacerbates the condition. Avoiding food that worsen the symptoms can help to manage the condition.

Conclusion

Crohn’s disease is a complex condition that has multifactorial causes. The relationship between the gut bacteria and the condition is under extensive ongoing research. While it has been understood that gut dysbiosis worsens symptoms associated with it, research is still required on how it influences and, furthermore, how it could be managed. Current studies favor the moderate use of antibiotics, probiotics, and diet modifications to manage Crohn’s disease.