What do gut microbes have to do with the lungs? Well, more than researchers once thought. A new study from the University of Michigan found that gut microbes can make their way into the lungs of critically ill people.
The group’s research into this phenomenon started with a rodent model of sepsis. In fact, it was shown in the 1950s that treating lab animals with antibiotics in advance of trauma or illness helps protect the lungs and increases survival. The current study, published in Nature Microbiology, looks at 68 human patients with acute respiratory distress syndrome
ARDS is a lung disease that occurs in critically ill patients - those with sepsis, pneumonia, or physical trauma to the lung. In ARDS, inflammation resulting from the illness or injury causes fluid to leak into the lungs, making it difficult to breathe - this process decreases the amount of oxygen that makes it into the blood to feed the rest of the body. Since patients with ARDS are already critically ill, the survival rate is only around 30-50%.
According to study author Robert P. Dickson,
“our results suggest that in our past attempts to find treatments for sepsis and ARDS, we may have been overlooking a major part of the story. Virtually all of our attempts to treat these critical illnesses have been aimed at fixing the disordered inflammation and tissue injury we can see in our patients. But our study raises the possibility that this inflammation and injury may actually be downstream consequences of an upstream source: disordered bacterial communities in the gut and lung.”
Dickson seems to suggest that the focus of current treatments needs to change. A disordered microbiome - a condition termed “dysbiosis
” - may actually be to blame. Dysbiosis is already associated with conditions such as inflammatory bowel disease, cancer, and even obesity. It can also result from cases of small intestinal bacterial overgrowth and small intestinal fungal overgrowth (termed SIBO or SIFO, respectively).
In fact, hospitals in other countries often treat uninfected critically ill patients with antibiotics. The idea is to suppress their microbiome, thus decreasing the risk for further complications or death. This type of gratuitous antibiotic usage is not common in the United States - there’s too much worry over generating antibiotic resistance.
This study suggests that the gut microbiome is intimately linked with the health of other parts of the body. Dickson sums it up well,
“in the long run, we need to start thinking of the microbiome as an organ that can fail in critically ill patients.”
Sources: American Lung Association
, Nature Microbiology