The microbiome of the critically ill patient

Advances in the understanding of the human microbiome outside of the ICU have led investigators to consider the role of the microbiome in critical illness. The picture that is being elucidated is one of dysbiosis occurring at multiple sites in the critically ill patient. This review describes the changes that occur in the various microbiomes of a critically ill patient, the implications of these changes and shows how advances in the understanding of dysbiosis may lead to microbiome-targeted therapies.

Critically ill patients undergo dysbiosis at several organ sites including the skin, gastrointestinal system and the lungs with loss of microbial diversity and a propensity for potentially pathogenic organisms to dominate a particular microbiome. These microbiome changes appear to be predictive of clinical outcome. While the use of fecal microbial transplantation has been demonstrated to be an effective treatment for recurrent Clostridium difficile infection, the use of fecal microbial transplantation and other microbiome modifying therapies may have a role in managing critical illness in the ICU.

A growing understanding of the microbiome in the critically ill may modify current dogma regarding the pathogenesis of sepsis and other life-threatening conditions seen in the ICU, thereby fundamentally changing antibiotic stewardship and the management of the critically ill patient.