Dramatic Changes of the Gut Flora Immediately After Severe and Sudden Insults

Background The gut flora is crucially involved in host homeostasis. However, the changes in the gut flora during the early phase of a critical illness are unknown. Aims We investigated the changes in the gut flora at an early phase of severe insult in critically ill patients. Methods Fifteen patients who experienced a sudden and severe insult were studied, along with 12 healthy volunteers as the control group. Fecal samples were acquired from the subjects by swabs of the rectum within 6 h after admission to the emergency room (day 0). Samples were serially collected from patients until day 14. Samples were also collected from control subjects. Results On day 0, total bacterial counts were decreased to one-thousandth the number of the control subjects, in particular, obligate anaerobes and Lactobacillus were significantly decreased. In addition, on day 0, the major short-chain fatty acids of the patients were significantly lower than those of the control subjects. The gut flora and the concentrations of major short-chain fatty acids did not recover to normal levels. In contrast, Enterococcus and Pseudomonas increased during the study period. Conclusions The gut flora in critically ill patients changed immediately after a severe insult. The concentrations of the three major short-chain fatty acids were immediately decreased in tandem with the destruction of the gut flora. The gut flora and the concentration of major short-chain fatty acids did not improve during the first 2 weeks after hospital admission. At the same time, the number of harmful bacteria gradually increased.