Gut microbiome is altered by burns, affected by fluid resuscitation

Oct. 28, 2019

Major burns lead to changes in the gastrointestinal tract bacteria, and these alterations of the gut microbiome are influenced by resuscitation with intravenous (IV) fluids, according to animal studies reported in SHOCK: Injury, Inflammation, and Sepsis: Laboratory and Clinical Approaches, the official journal of the Shock Society. The journal is published in the Lippincott portfolio by Wolters Kluwer.

Potentially disease-causing gut bacteria are increased after a major burn, while large volumes of IV fluids promote recovery of beneficial bacteria, suggests the experiments by David Burmeister, PhD, of the U.S. Army Institute of Surgical Research and colleagues. They write, "This study is the first to show that the gut microbiome is altered following a large burn injury in pigs and that the gut microbiome may be influenced by the resuscitation strategy used."

Burns don't just cause skin damage – they result in physiological stress and inflammation that may lead to infections and other serious complications. While a growing body of research has shown that the gut microbiome has important effects for health and disease, little is known about how burns may alter the microbiome.

The researchers examined changes in the gut bacteria after burns and how those alterations are affected by fluid resuscitation. Major burns, covering 40 percent of body surface area, were induced in anesthetized swine. Because their skin and gastrointestinal tract are similar to those of humans, pigs are an important model for studying burns and their treatment. The animals then received low- or high-volume fluid resuscitation or no IV fluids. Effects on gut microbiome diversity – the proportions of different types of bacteria – were analyzed by isolating and analyzing bacterial DNA.

The results showed significant changes in the gut microbiome after burns, with disruption of the normal balance between different groups of bacteria. Findings included a "hyperacute spike" in one major group called Proteobacteria, which includes many potentially pathogenic (disease-causing) organisms.

In contrast, high volumes of resuscitation fluids seemed to promote recovery of potentially beneficial microbes, such as Bacteroides bacteria. Since Bacteroides plays a role in converting sugar into energy, this shift might help in coping with the increased metabolic demands on the body after burns. Fluid resuscitation also prevented increases in certain opportunistic bacteria, which might protect against the risk of sepsis and other serious infections.

Resuscitation fluids also seemed to affect some functional proteins in the gut – for example, heat shock proteins that promote resistance to stress-induced cell damage. That provides a clue to understanding how fluid resuscitation helps the body recover from inflammation and other metabolic changes after burns.

Despite increasing evidence on the role of the gut microbiome, there has been little information on how bacterial diversity in the gut is affected by burns and their treatment. While early, aggressive fluid resuscitation is a key part treatment for burns, debate continues over the resuscitation strategies used.

Dr. Burmeister and colleagues call for further studies to clarify shifts in microbiome diversity after burns, and how these changes affect the outcomes of burns and responses to fluid resuscitation. Future research might lead to new treatments targeting the microbiome – for example, using fecal transplant or antibiotics – to promote recovery after burns.

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