The gut microbiome and the mechanism of surgical infection

Abstract

Background: Since the very early days of surgical practice, surgeons have recognized the importance of considering that intestinal microbes might have a profound influence on recovery from surgical diseases such as appendicitis and peritonitis. Although the pathogenesis of surgical diseases such as cholelithiasis, diverticulosis, peptic ulcer disease and cancer have been viewed as disorders of host biology, they are emerging as diseases highly influenced by their surrounding microbiota.

Methods: This is a review of evolving concepts in microbiome sciences across a variety of surgical diseases and disorders, with a focus on disease aetiology and treatment options.

Results: The discovery that peptic ulcer disease and, in some instances, gastric cancer can now be considered as infectious diseases means that to advance surgical practice humans need to be viewed as superorganisms, consisting of both host and microbial genes. Applying this line of reasoning to the ever-ageing population of patients demands a more complete understanding of the effects of modern-day stressors on both the host metabolome and microbiome.

Conclusion: Despite major advances in perioperative care, surgeons today are witnessing rising infection-related complications following elective surgery. Many of these infections are caused by resistant and virulent micro-organisms that have emerged as a result of human progress, including global travel, antibiotic exposure, crowded urban conditions, and the application of invasive and prolonged medical and surgical treatment. A more complete understanding of the role of the microbiome in surgical disease is warranted to inform the path forward for prevention.

Fig. 1

Host–microbiome dynamics in the gut during surgery. The normal microbiota constitute a major defence mechanism against the colonization and persistence of pathogenic bacteria (pathobiota), which are transiently encountered during hospitalization. Pathobiota are excluded by various mechanisms including competition for resources as they are outnumbered by the microbiota, secretion of antibiotics by the microbiota, and induction of antimicrobial peptides and immune elements induced by the microbiota.

Fig. 2

Host-microbiome dynamics in the gut during surgery. a When surgical injury is limited by minimally invasive techniques and attenuated physiological stress, the impact of antibiotic use on the microbiota is also limited, allowing the normal microbiota to refaunate and provide competitive exclusion to any transient pathobiota. b When surgical injury is severe and prolonged, causing a delay in resumption of normal foodstuff, refaunation of the microbiome can become impaired. This may result in a period of vulnerability to colonizing pathobiota, the consequences of which can be a loss of systemic immune function from lack of tonic immune stimulation by the microbiota. PSA, polysaccharide A; DC, dendritic cell, TLR, toll-like receptor