Scientists are now finding that the body's natural flora of microorganisms - microbiome - may be more associated with critical illnesses than previously thought.

These findings, published in Nature Microbiology, could redirect the focus of treatment, particularly in intensive care cases.

The research team discovered that in mice with sepsis, and in humans with acute respiratory distress syndrome (ARDS), bacteria from the gut were ectopically located in the lungs.

ARDS is a condition where the air sacs in the lungs get filled with fluid thus taking away available air space from oxygen. It results in poorer respiration and lower oxygen levels in the blood and the organs.

This, in turn, can lead to damaged organs and collapsed lungs. ARDS can be lethal if left unchecked.

Usually, ARDS occurs with other conditions. Sometimes these conditions even lead to ARDS. These include sepsis, an infection of the bloodstream; severe bleeding; chest injuries; and pneumonia, which is an infection of the lungs.

It has long been known that the population of bacteria in the gut is somehow related to lung illnesses. In fact, other countries routinely suppress the gut bacteria of ICU patients to decrease their risks of organ failure.

More than that, the gut microbiome has been increasingly linked with the overall health of a person. Diseases like Crohn’s disease, obesity, and ulcerative colitis have been connected to the gut microbiome.

The immune response, inflammation, and neurological diseases, all well outside the realm of the gut, have also been linked to the gut microbiota.

Thus, in the current paper, lead authored by Robert P. Dickson, M.D at the Division of Pulmonary and Critical Care Medicine at the University of Michigan Medical School, the team explored how the microorganisms in the gut influenced or reacted to lung conditions.

In their experiment, the team used genetic tools and both culture and non-culture techniques. They used mice with sepsis and human patients with ARDS.

They found that compared to normal patients, the lungs of those with ARDS or sepsis were dominated by bacteria that would typically be found in the gut and would otherwise be unable to survive in the lungs.

Further, they found that the levels of the molecule TNF-α were strongly associated with the ectopic bloom of gut bacteria in the lungs.

According to the authors, their findings imply that the disruption of the body’s microbial ecology traps the patient in a cycle. When the body microbiome changes, the immune system reacts through inflammation which injures lung tissues, which in turn, creates an environment in the lungs that gut bacteria can exploit and colonize, thus cementing the cycle.

Their findings contribute to a quickly growing body of knowledge about the gut microbiome and health. These also indicate that current clinical practice may have been targeting the wrong thing. They offer a new target: bacterial communities.

Dickson said their study raises the possibility that this inflammation and injury may actually be downstream consequences of an upstream source, which is disordered bacterial communities in the gut and lung. MIMS