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Gut Microbiota and IBS

By Chandreyi Banerjee

"All disease begins in the gut," - Hippocrates

It is a simple mathematical reality that we are more bacteria than human. The number of microorganisms in the stomach outnumbers human cells by a factor of ten. The human genome contains around 20,000 protein-coding genes. The microbial genome's coding capacity is predicted to be 150 times greater. This deceptively basic fact can distinguish the 7.9 billion people on the planet who all share the same genetic code. It can explain why some people are more prone to mosquito bites than others or why some people have better immunity than others. This article is primarily concerned with the relationship between the microbiome and irritable bowel syndrome (IBS)

What is the microbiome?

The microbiome is described as the collective genomes of microorganisms (bacteria, bacteriophage, fungus, protozoa, and viruses) that reside inside and on the human body, particularly the gut. Many of these microorganisms are beneficial in that they aid in digestion, regulate our immune system, protect against other bacteria that cause disease, and produce vitamins such as B vitamins B12, thiamine and riboflavin, and Vitamin K, which is required for blood coagulation. Thus, the microbiome is essential for human development, immunity, and nutrition.

Microbiome alteration-dysbiosis

An alteration of the microbiome or dysbiosis is characterized as a disruption to the microbiota homeostasis caused by an imbalance in the microflora. Diabetes, rheumatoid arthritis, muscular dystrophy, multiple sclerosis, and fibromyalgia have all been linked to microbiota dysfunction. Disease-causing microorganisms build over time, altering gene activity and metabolic processes and producing an aberrant immune response to chemicals and tissues usually present in the body. It has been discovered, for example, that the gut microbiota differs between obese and thin twins. In a research study, obese twin mice had fewer bacteria and higher amounts of enzymes, implying that they are more efficient at digesting food and extracting calories.

What is IBS?

Irritable bowel syndrome (IBS) is a common digestive disorder that affects a large number of people. Stomach aches, bloating, diarrhoea, and constipation are some of the symptoms. These tend to come and go throughout time, lasting a few days, weeks, or months. It is often a lifelong problem, with male to female ratio of 2:1 and an estimated prevalence of 12%. The primary criterion for meeting an IBS diagnosis is persistent abdominal pain in the absence of anatomical or biochemical abnormalities.

Role of the Microbiome in diagnosing IBS

Researchers have discovered that patients with IBS have greater bacterial counts in the proximal small intestine than healthy controls, known as Small intestinal bacterial overgrowth (SIBO). SIBO is typically diagnosed using a breath test that analyzes the quantity of hydrogen in the breath after consuming lactose-containing beverages. Lactulose is a sugar that our systems are unable to absorb, thus it is fermented by bacteria in the intestine. If the amount of hydrogen in your breath is high a short time after drinking the lactulose solution, it's thought to indicate a problem. However, the results of the clinical trials for this method of diagnosis have mostly been inconclusive.

Ways to alter the microbiome to treat IBS

1. Probiotics

Usually probiotics are certain types of Streptococcus, Lactobacilli, and Bifidobacteria, but also other non-pathogenic bacilli such as E. coli-Nissle and yeasts such as Saccharomyces boulardii. The best known and most widely used probiotics are Lactobacillus plantarum 299v, Lactobacillus rhamnosus LGG, Lactobacillus reuteri, Lactobacillus acidophilus, Lactobacillus casei and Bifidobacterium infantis, lactis or brevis. Probiotics thus can be administered not only as functional foods, but also in pharmaceutical forms similar to medicines.

2. Antibiotics

Rifaximin is a non-systemic antibiotic that has been shown in multiple clinical trials to be effective in improving global IBS symptoms, bloating, abdominal pain and stool consistency.

In addition, rifaximin appears to directly affect bacterial metabolism, colonic methane production and the expression of virulence factors, and effects on host mucosal inflammation and bacterial attachment.

3. Fecal transplant

This is a unique method that is not currently suggested outside of clinical studies, However, two recent experiments have yielded contradictory findings. In a double-blind study of individuals with moderate-to-severe IBS, 65 percent of active-treatment patients experienced symptom improvement compared to 43 percent of controls. In contrast, a similar group study discovered that while FMT was efficient in modifying the microbiome, placebo resulted in larger improvements in symptom and quality of life scores.


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