Hello everyone and welcome to this week's blog post where I will follow on from last week's post (if you haven't already read it, click here) by exploring the use of the microbiome in medicine. In this post, I will discuss species-specific antibiotics and how we can influence the microbiome for therapeutic effects, before moving on to explain the future of microbiome medicine.
As I explained in my last blog post, according to many microbiologists, antibiotics act as 'atom bombs' to our microbiome, in that they destroy all bacteria, including the ones that make up our own microbiome. This often creates massive problems for us, as it both prevents us from digesting certain proteins and also means that harmful bacteria and other microbes are able to grow and take their place in our body. As such, this is yet another reason why antibiotics should only be taken when absolutely necessary, not as a precaution.
One way we could reduce the problem is by investing in research to develop a new type of antibiotic. This could potentially allow us to not only reduce the number of strains of antibiotic-resistant bacteria (read my blog post here for more information) but also help preserve our resident microbes.
The development of these precise, species-specific antibiotics is not easy though. According to leading microbiology Jenn Leeds, one of the major drawbacks with developing such medicine is that it would not solve the problem of antibiotic-resistance bacteria overnight since if the patient doesn't finish the course of antibiotics, then an antibiotic-resistant strain could still develop for that bacteria species. Despite this, antibiotics which work on a narrow range of bacteria would not affect any other species of bacterium, so antibiotic-resistant strains of these bacteria would not develop.
Additionally, there is hope that species-specific bacteria have a minimal impact on the human microbiome, in particular the gut flora. While this would make sense in theory, as the antibiotics would only destroy the specific pathogenic bacterium species which they target, it is not yet known whether it would work in practice. Furthermore, in order to use this form of antibiotics, doctors would first have to analyse the infection and ascertain what species of bacteria caused it. While this would be possible in some cases, in others, for example when someone presents with sepsis in A&E, broad-spectrum antibiotics would have to be used immediately as there would be no time to determine which species of bacteria is causing it.
Likewise, infections are often caused by multiple pathogens at the same time - these types of infection are called poly-microbial. In this case, many species-specific antibiotics would have to be combined for the treatment to be effective. Not only could these drugs have adverse effects when combined with each other, but their cost could prohibit their use on the NHS.
As the NHS has limited resources, it must make sure that the health benefits treatment can provide are balanced with their cost, so that the quality of life for the greatest number of people can be maintained. Species-specific antibiotics would be incredibly expensive, whereas broad-spectrum antibiotics are much cheaper. Indeed, broad-spectrum antibiotics are so cheap that farmers often use them in livestock farming, as it is cheaper to feed the livestock antibiotics than to ensure they live in hygienic conditions.
Moreover, a considerable amount of research has been done to influence the resident human microbiome for therapeutic effect, allowing us to treat many diseases. One of the most promising methods of doing this is through the use of faecal microbiota transplants.
While the use of faecal microbiota transplants is not permitted in the UK under NICE guidelines, this method of treatment is commonly used around for the world. For example, faecal microbiota transplants are often used as a treatment of recurrent Clostridium difficile in the United States. In this treatment, the stool is collected from a healthy donor (often a relative to improve its effectiveness) and then processed, before being transferred endoscopically into the gastrointestinal tract of the recipient. During the processing stage, the recipient and donor are screened for viruses such as Hepatitis A, B and C, as well as HIV, while the sample is screed for parasites and other pathogens such as Clostridium difficile.
Faecal microbiota transplants are often used to treat recurrent Clostridium difficile, as it repopulates the gut microbiome with healthy microbes from the host, which displace the Clostridium difficile bacteria. Indeed, studies have shown that faecal microbiota transplant is able to successfully treat 80-90% of cases of recurrent Clostridium difficile. This improvement in our treatment of Clostridium difficile is significant, as management for this infection costs approximately €3 billion per year in Europe alone. Nevertheless, due to concerns with infection, Faecal microbiota transplant treatment is not widespread in the UK.
A further method of influencing the immune system is through the use of probiotics. Nonetheless, this is easier said than done! Probiotics are live bacteria and yeasts that are often added to yoghurts and bought my health-conscious consumers. However, before buying them, there are a few things that you should know. Firstly, there is no guarantee that there are enough bacteria to have an effect on the body. Secondly, the yoghurt's probiotics are not natural to the gut, so it is unlikely that they will be able to implant themselves into the gut microbiome and have a lasting impact.
In the future, it is hoped that we can use our knowledge of the human microbiome to create personalised and more effective medication. This could possibly occur by 'fingerprinting' everyone's microbiome. Like fingerprints, everyone has a unique microbiome. As such, by cataloguing the genes and species of microbe that makeup someone's microbiome, scientists would be able to establish someone's past exposures to pathogens and predispositions to disease. According to Alex Kostic, who is an assistant professor of microbiology at Harvard Medical School, fingerprinting the microbiome could also help develop precision-targeted treatments. Furthermore, we might also be able to use artificial intelligence to predict the correct combination of bacteria to use in treatment.
Moreover, the microbiome may also have many applications in cancer treatment. One of these applications is in gut cancer, as the tumours which form can contain these microbes inside them. These microorganisms then act as biomarkers, which can be targetted during cancer treatment. In addition, researchers are also attempted to influence the microbiome in a way which improves cancer treatment. Nonetheless, these treatments are all in the early stages and much more research in this area is required before treatment is available for public use.
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Sources:
I Contain Multitudes by Ed Yong
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