Antibiotics And Your Microbiome: Understanding The Impact On Gut Health

Overview

The discovery of antibiotics marked a significant step forward for medicine. Antibiotics revolutionised the treatment of deadly bacterial infections and saved countless lives. Bacteria can be found everywhere – including inside the human body, with the human gut hosting trillions. Many bacteria are harmless or even helpful to our health, and the gut microbiome is a great example of this. Read on to find out more about the importance of the gut microbiome and explore the impacts of antibiotic usage on our internal ecosystems.

What is the gut microbiome?

The microbiome refers to the habitat and microorganisms (the microbiota) that live within it. Microorganisms are tiny organisms including bacteria, viruses and other single-cell organisms.^1,2 The human gut is home to thousands of different strains of microbiota. Our gut and immune systems have evolved to co-exist with microbiota in a collaborative relationship.¹ The composition of the gut microbiota varies between individuals. This composition can be affected by a range of factors including diet, smoking, physical activity, health conditions, age, gender, ethnicity and use of drugs or medications.²

Why is the gut microbiome so important?

The gut microbiome has several different functions that are beneficial to the individual.

Metabolism

Humans have a wide palate, but our innate ability to digest certain carbohydrates is quite limited. The range of microorganisms in our gut is what enables us to digest a range of foods – including vegetables, fruits, nuts and wholegrain cereals. The microbiota ferments these complex carbohydrates and turns them into simpler forms that the human body can absorb. Microorganisms also assist in acquiring nutrients (including vitamins, calcium and iron) and affect how medicines are metabolised (for example, paracetamol and digoxin).^1,2

Protection

By lining the walls of the gut and secreting antimicrobial compounds, the microbiota creates a hostile environment against harmful bacteria and fungi. that physically and chemically prevents them from establishing and proliferating in the gut. The microbiota also contributes to the development and function of the immune system, with at least 80% of all antibodies produced by adults originating from the intestines.^1,2

Gut barrier

The gut microbiota helps to regulate the expression of cells and factors that our body uses to maintain the integrity of the intestinal walls. Some bacteria strains produce proteins and mucous that are prevent damage caused to the gut wall by inflammation.^1,2

How do antibiotics affect the gut microbiome?

Antibiotics are medicines used to treat bacterial infections by either killing or stopping the growth of bacteria. Although we use antibiotics against harmful bacteria, it is difficult to limit the antibacterial effect to specific bacteria. Antibiotics target essential processes or structures at the cellular level and stop them from working properly. These cellular processes and structures can be very similar across different bacterial species, including the ones found in the gut microbiota.³

Antibiotics are unable to distinguish the harmful bacteria that is causing the infection, and the harmless bacteria in the gut microbiota resulting in collateral damage to our microbiota.Thus, when harmful bacteria are eliminated by antibiotics, the surrounding microbiota may also suffer. Consequently, the diversity of the gut microbiota is reduced as certain species are eradicated by the antibiotic, leaving unaffected species to continue to thrive.²

What are the impacts of antibiotics on the gut microbiome?

Diarrhoea

Diarrhoea is commonly listed as a side effect of most antibiotics and can occur for up to 8 weeks after starting antibiotic treatment. Antibiotic-associated diarrhoea often happens when our normal gut microbiome is disrupted by antibiotics, which enables the growth of microorganisms that cause diarrhoea.²

Clostridium difficile-associated infection

Clostridium difficile (C. difficile) is a bacterium normally present in the microbiome in small numbers without causing disease. However, when allowed to proliferate, they can release toxins that cause C. difficile-associated infection. This can be unpleasant for most people (causing symptoms of diarrhoea, nausea, abdominal pains and nausea), but can quickly develop into a serious, even fatal, infection for others.²

Metabolic conditions

Since the gut microbiota plays a heavy role in metabolism, it seems reasonable that changes in the gut microbiota can be linked to body weight. Studies have shown that people and animals that take antibiotics for a long time tend to have a heavier body weight. This raises the risk for obesity, and also metabolic conditions that are linked to obesity including heart disease, liver problems and type 1 diabetes.^2,4

Allergies

An association has been seen in the use of antibiotics in early childhood and allergies, including asthma. Unlike adults, gut microbiomes are not yet fully developed in young children,  them more vulnerable to being affected by antibiotics. In a study of infants aged under 2 years a delay in microbiota development was observed after antibiotic use.^2,4

Antibiotic resistance

We’ve mentioned before the critical role antibiotics play in medicine, however, there is a growing concern that our current antibiotic toolkit may not continue to be as effective as before. This is because while antibiotics are very good at targeting certain bacteria by attacking specific weak points, other bacteria can become resistant to the antibiotics.

The gut microbiome is home to thousands of bacteria, providing a perfect reservoir for potentially resistant bacteria. With repeated use, the resistant bacteria are more likely to survive, making the antibiotic less effective at treating infections over time. When antibiotics don’t work as well, it can make it harder to treat infections, making people sicker for longer and leading to more serious health problems.

Using antibiotics sensibly

Antibiotics are an important part of treating infections. We can all help to slow the rise of antibiotic resistance by choosing to use antibiotics sensibly and:

• Avoiding the use of antibiotics when they are not required, such as in viral or fungal infections
• Following the advice of the prescriber when using antibiotics
• Looking after our health and hygiene to avoid becoming ill in the first place

Summary

The bacteria living in our gut are like guardians, protecting our intestines from harm and helping digestion to run smoothly. Without them defending against harmful substances, our gut health could suffer, leading to long-term health conditions. Antibiotics could wipe out parts of our microbiota and leave us vulnerable to a multitude of problems, including diarrhoea at the individual level and antibiotic resistance at a widespread scale.

FAQs

What role do probiotics play in gut health?

Probiotics are live microorganisms added to foods or supplements, that are claimed to have various health benefits. Probiotics often include bacteria that are normally found as part of our gut microbiomes, such as Lactobacillus and Bifidobacterium. Probiotics are generally safe for healthy people to take, but the health claims are not always proven.¹

How long does it take for the gut to recover after taking antibiotics?

The time taken for recovery depends on the antibiotics and the individual. In adults, the gut microbiota usually takes between one and two months to return to its normal condition. However, some strains of bacteria may take up to years to reflourish.^2,4