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Bacteria: an overlooked factor in interstitial lung disease?

Did you know that your lungs are full of bacteria? We once thought that the lungs were 'sterile' (free of bacteria), but we now know these little creatures are also on the membrane of our airways. Researchers think they may even play a role in the development of interstitial lung disease (ILD). So let's take a closer look at our small companions and find out what we know about them!

There is a symbiosis: we need the bacteria and they need us.

As humans, we are the host for microorganisms on basically our entire body. This whole aggregate of microorganisms is called the human 'microbiota'. One of the places where these microorganisms reside is the lungs, called the lung microbiota, or 'lung microbiome'. Although it may sound a little spooky that we are covered in bacteria, they are actually essential for our health. There is a symbiosis: we need the bacteria and they need us. But alterations in the quantity or composition of the microbiome have also been implicated in many diseases, and recently ILD became one of them. Researchers of the University of Michigan, USA, found that patients with idiopathic pulmonary fibrosis (IPF) (the most commonly studied ILD) often have an altered microbiome.


They found that the relative dominance of specific bacteria in the lungs was associated with disease progression and/or acute exacerbation. And an increased total bacterial burden was also found to be related with ILD. So, does this mean we have to eradicate as much bacteria as we can in patients with ILD? According to the researchers, that might be a bit blunt. The microbiome is dynamic and interacts with the host immune system on one hand and with the environment, on the other.

It might be possible that certain bacteria invading this otherwise symbiotic relationship could initiate an immune response and trigger or propagate an existing susceptibility to ILD. Conversely, changes in the microbiome could also be the result of an already altered immune system. Maybe in the future, antibiotic or immunization against pathogens could become potential adjuvant therapy in ILD. When the role of the pathogens is identified, targeting them might limit their impact on the fibrosis. Also, the discovery of the role of the microbiome in ILD might be an important step for treating this disease, while it could also serve as a biomarker and help us to understand how ILD arises. 

Margaret L. Salisbury, MeiLan K. Han, Robert P. Dickson, and Philip L. Molyneaux (2017) Microbiome in interstitial lung disease: from pathogenesis to treatment target. http://dx.doi.org/10.1097/MCP.0000000000000399.