To investigate the effects of fecal microbiota transplantation (FMT) on intestinal microbiome and organism in patients with severe pneumonia during the convalescence period.

A prospective non-randomized controlled study was conducted. From December 2021 to May 2022, patients with severe pneumonia during the convalescence period who received FMT (FMT group) and patients with severe pneumonia during the convalescence period who did not receive FMT (non-FMT group) admitted to the First Affiliated Hospital of Guangzhou Medical University were enrolled. The differences of clinical indicators, gastrointestinal function and fecal traits between the two groups were compared 1 day before and 10 days after enrollment. The 16S rDNA gene sequencing technology was used to analyze the changes of intestinal flora diversity and different species in patients with FMT before and after enrollment, and metabolic pathways were analyzed and predicted by Kyoto Encyclopedia of Genes and Genomes database (KEGG). Pearson correlation method was used to analyze the correlation between intestinal flora and clinical indicators in FMT group.

The level of triacylglycerol (TG) in FMT group was significantly decreased at 10 days after enrollment compared with before enrollment [mmol/L: 0.94 (0.71, 1.40) vs. 1.47 (0.78, 1.86), P < 0.05]. The level of high-density lipoprotein cholesterol (HDL-C) in non-FMT group was significantly decreased at 10 days after enrollment compared with before enrollment (mmol/L: 0.68±0.27 vs. 0.80±0.31, P < 0.05). There were no significant differences in other clinical indexes, gastrointestinal function or fecal character scores between the two groups. Diversity analysis showed that the α diversity indexes of intestinal flora in FMT group at 10 days after enrollment were significantly higher than those in non-FMT group, and β diversity was also significantly different from that in non-FMT group. Differential species analysis showed that the relative abundance of Proteobacteria at the level of intestinal flora in FMT group at 10 days after enrollment was significantly lower than that in non-FMT group [8.554% (5.977%, 12.159%) vs. 19.285% (8.054%, 33.207%), P < 0.05], while the relative abundance of Fusobacteria was significantly higher than that in non-FMT group [6.801% (1.373%, 20.586%) vs. 0.003% (0%, 9.324%), P < 0.05], and the relative abundance of Butyricimonas, Fusobacterium and Bifidobacterium at the genus level of the intestinal flora was significantly higher than that in non-FMT group [Butyricimonas: 1.634% (0.813%, 2.387%) vs. 0% (0%, 0.061%), Fusobacterium: 6.801% (1.373%, 20.586%) vs. 0.002% (0%, 9.324%), Bifidobacterium: 0.037% (0%, 0.153%) vs. 0% (0%, 0%), all P < 0.05]. KEGG metabolic pathway analysis showed that the intestinal flora of FMT group was changed in bisphenol degradation, mineral absorption, phosphonate and phosphinate metabolism, cardiac muscle contraction, Parkinson disease and other metabolic pathways and diseases. Correlation analysis showed that Actinobacteria and prealbumin (PA) in intestinal flora of FMT group were significantly positively correlated (r = 0.53, P = 0.043), Bacteroidetes was positively correlated with blood urea nitrogen (BUN; r = 0.56, P = 0.029) and complement C3 (r = 0.57, P = 0.027), Firmicutes was positively correlated with BUN (r = 0.56, P = 0.029) and complement C3 (r = 0.57, P = 0.027), Fusobacteria was significantly positively correlated with immunoglobulin M (IgM; r = 0.71, P = 0.003), Proteobacteria was significantly positively correlated with procalcitonin (PCT; r = 0.63, P = 0.012) and complement C4 (r = 0.56, P = 0.030).

FMT can reduce TG level, reconstruct intestinal microecological structure, change body metabolism and function, and alleviate inflammatory response by reducing the relative abundance of harmful bacteria in patients with severe pneumonia during the convalescence period.

Fecal microbiota transplantation; Severe pneumonia; Convalescence period; Intestinal microbiome