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.