Features of the colon microbiome in mild COVID-19

Abstract

Introduction. The stability of the composition and physiological functions of the colon microbiome is maintained by specific mechanisms of symbiosis with the macroorganism, which was formed in the process of long-term adaptation of coexistence in the form of a single ecological system. Identification of the features of the colon microbiota of patients with infectious pathologies, including COVID-19, continues to attract special attention of scientists. The purpose of the study: to investigate and analyze the human colonic microbiome in mild COVID-19, including in a comparative aspect with the indicators of practically healthy individuals. Materials and methods. Microbiological (bacteriological and mycological) examination of clinical material (stool) was performed in 24 patients with covid-associated communityacquired pneumonia of mild severity and in 29 healthy volunteers who did not have any complaints of gastrointestinal disorders and considered themselves to be practically healthy. The study participants included 52.84% (28) women and 47.16% (25) men. The average age of the study participants was 40.16±5.25 years (from 29 to 48 years). Clinical material (the last portion of fresh feces) was collected with a sterile spatula and placed in sterile pharmacy vials. Isolation and identification of isolated pure cultures were performed according to generally accepted methods. An electronic database was created in Excel® 2016 (Microsoft). Statistical analysis was performed using MS® Excel® 2016™ and Statistica® 7.0 (StatSoft Inc., USA). The reliability of data for independent samples with a distribution of arrays close to normal was calculated by the Student's t-test, with uneven distribution – by the Wilcoxon-Mann-Whitney U test. Differences were considered significant at p<0.05. Results. It has been established that in patients with mild coronavirus infection, a stable tendency to decrease the population level of bifidobacteria and a statistically significant decrease (P<0.05) in the bacteria of the genus Lactobacillus is formed in the colon. In contrast, in the colon of patients with COVID-19, there is a stable tendency to increase the population level of enterobacteria of the genus Proteus, bacteria of the genus Staphylococcus and yeast-like fungi of the genus Candida. The population level of Escherichia coli practically does not change, but in patients with mild COVID-19 it reaches the highest level in the colon (9.49±0.90 LgKUO/g). There is a 60.05% decrease in bifidobacteria and a 3.92-fold decrease in lactobacilli in the colon of patients with mild COVID-19. The decrease in the population level and the role of bacteria of the genus Bifidobacterium and Lactobacillus in the Quorum sensing system contributes to a decrease in their protective functions and control over microbiota self-regulation, which leads to colon contamination with conditionally pathogenic enterobacteria E. coli with altered properties, E. coli Lac-, enterobacteria of the genus Proteus, Klebsiella, Enterobacter and Citrobacter. Conclusion. The decrease in the number of bacteria of the genus Bifidobacterium and Lactobacillus in the colon biotope in patients with mild COVID-19 contributes to the contamination of the intestine with conditionally pathogenic enterobacteria, the population level of which reaches values at which the development of infectious and inflammatory processes is possible.