Burn injuries lead to changes in the gut microbiome

One of the leading causes of death among burn injury patients is infection, and specifically sepsis. It is believed that in individuals with compromised immune systems, sepsis is caused by a bacterial infection that leads to an inflammatory response throughout the whole body. The powerful inflammatory response changes blood pressure and causes cell stress in the body, which is most often fatal. Additionally, many studies suggest that Gram-negative (this classification is based on cell membrane composition) bacterial infections have something to do with sepsis. Published in Plos One, researchers in Chicago studied burn patients and mice to see if burn injury changed the gut in such a way that it becomes easier for Gram-negative bacteria to thrive.

Fecal samples were collected from 4 burn patients at Loyola University Medical Center. The total body surface area (TBSA) of burns for each patient was 25%, 32%, 44%, and 57%. A control group of 8 patients was used as well, made up of burn patients whose TBSA was less than 10%. A similar mice experiment was set up as well.

After comparing the fecal samples of the significantly burned patients and the controls, they found that fecal microbial richness was significantly higher in control patients. The burn patients with the highest TBSA had the most similar communities, and after 11 days the community of the 32% patient changed to more closely resemble that of the 44% and 57% patients. Sadly, the burn patients with 32%, 44% and 57% TBSA died from sepsis. Upon examination of the microbes collected in fecal samples from the burn patients, however, a relative abundance of bacteria was found from the family Enterobacteriaceae, which are Gram-negative.

The effects of burn injury were studied in mice as well, in order to determine if the human effects were reproducible in mice, if similar microbes are found in the mice gut, and if different locations in the gastrointestinal tract had different community characteristics. The small and large intestines were found to have very different microbiome composition. The abundance of Enterobacteriaceae was higher in the small intestine than the low intestine, but the abundance decreased from day one to day three. 

The intestinal wall can be injured because of burns, and if the ability for things to move through it is easier, then harmful bacteria may be able to move into the circulatory system and increase the risk of an inflammatory response. The proteins that hold cells together in the gut were studied, and they were found to be decreased in burn injury mice. This occurred at the same time as the increase of Enterobacteriaceae. While an established connection cannot be made yet, this study will hopefully lead to further research of the connection between Gram-negative bacteria and sepsis. 

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