The Gastrointestinal Microbiome in Critical Illness

The gastrointestinal microbiome is a diverse consortium of microorganisms inhabiting the intestinal tracts of all mammals that is essential to maintaining host animal health. Enteric microbiota dysbiosis (EMD) has been identified in humans and other animals with acute critical illnesses. Common pathophysiologic features of critical illness can cause EMD by altering the intestinal microenvironment. Antibiotics, proton pump inhibitors, and other therapies delivered in intensive care units are also associated with the induction of EMD. Once EMD is established, it can influence the progression of critical illnesses and increase susceptibility to sepsis, acute lung injury, and multiple organ dysfunction syndrome in critically ill patients. Therapies intended to alter the GI microbiome have reduced morbidity and mortality in humans and other animals with critical illnesses. There are few studies of the GI microbiome in critically ill dogs and cats, making this an important and promising area for future research. This lecture will review current knowledge regarding how host-microbiome interactions and therapeutic interventions that alter the GI microbiome play a role in the pathogenesis and pathophysiology of critical illnesses.