Gut microbes predict Covid-19 severity
The microbes that inhabit our intestines, scientists say, may hold the key to spotting - and treating - those most at risk from Covid-19...
The severity of Covid-19 symptoms in patients infected with the new SARS-CoV-2 coronavirus can be predicted based on the microbes they carry in their intestines, a new study has shown1. This means that considering the makeup of a person’s microbial community, known as their microbiome, alongside other relevant clinical data such as their past medical history and age, could be a powerful tool for triaging Covid-19 cases.
At the University of Massachusetts Medical School, Ana Maldonado-Contreras collected oral and stool samples from 63 COVID-19 patients classed as either moderate or severe cases based on their oxygen requirements in hospital. Patients with severe illness, the study revealed, had microbiomes that were significantly different from patients with more moderate disease.
In essence, the microbiome serves as a proxy marker for a patient’s biochemistry and immune function, reflecting overall health status, underlying diseases and factors such as eating habits and body weight.
This study of the microbial passengers that accompany us through life is not new. For decades, scientists have been striving to connect the complex communities of bacteria, viruses, fungi and archaea to health outcomes. It’s not an unintuitive link to make. The microbiome participates in numerous critical roles in the body, from educating the immune system to distinguish correctly between friend and foe, preventing more harmful microbes from gaining a toe-hold in the first place, and breaking down foods that we cannot to release nutrients that our cells can use. And all the time this list is growing as researchers uncover new ways in which our microbiomes help us to thrive2.
The human microbiome is effectively an ecosystem, like the Amazon rainforest or a coral reef, where myriad species coexist to form a complex, interdependent community. As such, a healthy microbiome depends on a harmonious relationship among the contributors. On the flip side, disruptions to this microbial interplay, termed dysbiosis, can cause disease or can act as an indicator for impending ill health.
Unfortunately, it is often difficult to say exactly which members of the microbiome are directly linked to an illness. This is because it is tricky to tease apart the complex interactions between the hundreds of thousands of microbial forms that are present, and their individual influences on each other and the human immune system. But, sometimes, changes in our microbiome, which are tied to disruptions in our immune system, can warn us of irregularities in our health.
Consequently, researchers believe that microbiome changes can act as indicators for disease risks, potentially allowing doctors to group and treat patients accordingly3. Nevertheless, the present lack of standardisation in patient samples, the populations being tested and analytical techniques being used mean that it can be hard to interpret these studies or produce consensus results5. So it’s not surprising that a team at the Chinese University of Hong Kong have also found that changes in the gut microbiome are related to disease severity in COVID-19 patients4, but the microbial changes they have highlighted are different to those identified by the Massachusetts team.
No one disputes that healthcare services globally are buckling under the strain of COVID-19, particularly in the intensive care setting. Until recently in the UK, thousands of people every day were being admitted to hospital with COVID-19, and a third of them were dying within a month of testing positive6. The ability to diagnose and triage patients rapidly, so the most high-risk individuals may be prioritised for access to limited equipment and medical attention, could save many lives. But there is still much to be done before the microbiome can be used as a medical tool in managing COVID-19. As with all such medical tools, they must undergo testing in clinical trials to meet rigorous scientific standards before they can be used in our hospitals.
According to Marcus Rauch, Chief Scientific Officer of the London-based start-up AlphaBiomics whose aim is to use the gut microbiome as a diagnostic tool against disease, “the human microbiome has been linked to disease onset, progression, and treatment response across multiple indications, and as such, efforts are underway to use microbiome diagnostics”. It’s not all a bed of roses though, and there is still a lot of groundwork to do before the microbiome becomes a routine part of our diagnostic procedures. As Rauch points out, although there are growing opportunities for clinical microbiome diagnostics, “there is a lack of regulatory guidance that outlines and clarifies specific requirements for [such] diagnostic products...”
So there is work to be done. All the same, despite the challenging road ahead for those aiming to harness information from our microbiome to develop innovative diagnostic tools, many argue that it is still a journey worth taking. The destination is a non-invasive, rapid and low-cost strategy to predict disease outcomes so healthcare professionals can more effectively triage patients and manage limited healthcare resources.