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...and what about microbes?

Lisa Jamieson says there are reasons beyond antimicrobial resistance to focus on antimicrobial stewardship and avoiding unnecessary antibiotics where possible

As a pharmacist, my training on antimicrobial stewardship focused on antimicrobial resistance. This is of course important.

We need to ensure that when we need them, effective antimicrobials are available to protect us from potentially fatal infections, as well as ensuring that complex procedures can be undertaken with a low risk of infection. As antimicrobial stewards, pharmacy teams support a system-wide focus on avoiding unnecessary antibiotic prescribing and promoting judicious use. 

But as well as aiming to ensure that we can still retain access to effective antibiotics for our population now and in the future, we need to look beyond antimicrobial resistance. What about the risks versus benefits to future health for an individual who takes a course of antibiotics when it is not actually needed? Shouldn’t we also be considering the potential short term and, importantly, long term side effects of antibiotics?

As a newly qualified pharmacist in the mid-1990s, the only gut microbe that was ever on my radar was Helicobacter pylori. This relatively recent discovery provided a new reason to use antibiotics – to eradicate the gut microbe responsible for peptic ulcers. 

The fact that the human gut was full of other beneficial microbes – that are needed to keep an individual healthy – was not something ever covered in my pharmacy training. It would be almost two decades later, when I was studying for an MSc in nutritional medicine, that I would learn in detail that gut microbes are essential for human health. Today, the gut microbiota is considered so important, and has so many beneficial and essential functions, that it is known as ‘the forgotten organ’.

The gut microbiota – the entire population of microbes that colonise the whole gastrointestinal tract – is responsible for many vital functions. Nutrient metabolism via microbial fermentation of carbohydrates leads to the synthesis of short chain fatty acids (SCFAs) such as butyrate, which are important for keeping the gut lining and the blood brain barrier healthy. They also have anti-inflammatory and anti-cancer properties.

“The friendly microbes living within our gut constantly stimulate the immune system”

Gut microbes are also important for the synthesis of some vitamins (such as K and B12), as well as antimicrobial substances that can kill off ‘bad bacteria’. Microbes also create biofilms along the lining of the gut, which can prevent colonisation by invading pathogens.

The friendly microbes living within our gut constantly stimulate the immune system in the gut-associated lymphoid tissue (GALT). This ensures the immune system is functioning optimally and ready to mount an attack when it meets a pathogen that may cause harm.

The microbiota gut-brain axis is the target of much research. We are learning about new ways in which there are direct communication channels between the gut and the brain, which can influence memory function, mental health, learning and mood. Studies have shown that a well-functioning microbiota is one that is diverse. Various lifestyle factors can impact on this. Importantly, a healthy dietary intake can have a beneficial impact on microbial diversity.

When broad spectrum antibiotics are taken to treat a pathogenic infection, they also kill off countless gut microbes. Antibiotics can have long-term consequences on the composition, ecology, resistance and function of the gut microbiota. Antibiotic-induced changes to the gut microbiota can lead to neuroinflammation, and antibiotic depletion of the gut microbiota can result in memory impairment.

Numerous studies have also shown that alterations in the gut microbiota can result in diseases including C. difficile diarrhoea, bowel disorders such as inflammatory bowel disease, type 2 diabetes, obesity, and colorectal cancer. We therefore need to try to take care of our gut microbiota to optimise our health and to prevent the onset of ill health in the future. 

Further reading

  • Anderson SC, Cryan JF, Dinan T. The Psychobiotic Revolution: Mood, Food, and the New Science of the Gut-Brain Connection. National Geographic (2017)
  • Cartwright P. Probiotic Allies: How to Maximise the Health Benefits of Your Microflora. Prentice Publishing (2011)
  • Fasano A, Flaherty S. Gut Feelings: The Microbiome and Our Health. MIT Press (2022)
  • Dudek-Wicher RK, Junka A, Bartoszewicz M. The influence of antibiotics and dietary components on gut microbiota. Prz Gastroenterol. 2018 doi: 10.5114/pg.2018.76005
  • Ramirez J, Guarner F, Bustos Fernandez L, Maruy A, Sdepanian VL, Cohen H. Antibiotics as Major Disruptors of Gut Microbiota. Front Cell Infect Microbiol. 2020 doi: 10.3389/fcimb.2020.572912
  • Silva YP, Bernardi A, Frozza RL. The Role of Short-Chain Fatty Acids from Gut Microbiota in Gut-Brain Communication. Front Endocrinol (Lausanne). 2020 doi: 10.3389/fendo.2020.00025 

Lisa Jamieson is a pharmacist and medical writer with specialist interest and an MSc in nutritional medicine. Find her on Twitter @LoveInYourTummy

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