[Analysis of intestinal patients' flora changes with severe pneumonia based on 16SrDNA sequencing technology]

To investigate the characteristics of gut microbiota dysbosis in patients with severe pneumonia using 16SrDNA sequencing.

A prospective observational research was conducted. The stool samples retained by natural defecation or enema within 2 days after hospital were collected from 16 patients with severe pneumonia admitted to department of intensive care unit (ICU) of General Hospital of Ningxia Medical University from June to December in 2018 and 10 persons for physical exam were enrolled as the healthy control group. The 16SrDNA sequencing technology was used to detect fecal flora and analyze biological information.

(1) 1 015 475 effective sequences were obtained from the stool samples from the severe pneumonia group and the healthy control group. Using 16SrDNA method, it was found that the average effective length of the sample sequence was 458.35 bp and the average sequence number of the total samples was 39 056.73. (2) Analysis of α diversity of gut microbiota showed that, compared with the healthy control group, the Ace index, Chao index and the Shannon index of gut microbiota diversity in the severe pneumonia group were significantly decreased [Ace index: 167.23 (143.14, 211.26) vs. 227.71 (214.53, 247.05), Chao index: 152.38 (138.09, 182.54) vs. 228.25 (215.49, 248.95), Shannon index: 2.37 (1.68, 2.89) vs. 3.39 (3.03, 3.63), all P < 0.01], and the Simpson index was significantly increased [0.21 (0.11, 0.33) vs. 0.07 (0.06, 0.12), P < 0.01], which indicated the gut microbiota diversity of the severe pneumonia group was decreased. (3) Analysis of β diversity of gut microbiota, principal coordinate analysis (PCoA) showed that gut microbiota structural with the healthy control group was similar, while that in the severe pneumonia group was different. Adonis analysis showed that the structural of the gut microflora revealing significant differences between the severe pneumonia group and the healthy control group (R² = 0.061, P = 0.05). (4) Analysis of phylum difference gut microflora showed that, compared with the healthy control group, the proportion of Firmicutes in severe pneumonia group was decreased [27.36 (18.12, 39.28)% vs. 52.25 (38.36, 63.82)%, P = 0.02], the proportions of Actinobacterias, Synergistetes and Fusobacterias were increased [2.30 (0.30, 4.80)% vs. 0.02 (0.00, 0.06)%, 0.36 (< 0.01, 0.57)% vs. < 0.01 (< 0.01, < 0.01)%, 0.01 (< 0.01, 0.08)% vs. < 0.01 (< 0.01, < 0.01)%, all P < 0.05]. (5) Analysis of genus difference gut microflora showed that, the proportions of Bifidobacterium, Ruminococcus, Pseudobutyrivibrio, Coprococcus, Lachnospira and Prevotella in the severe pneumonia group were significantly lower than those in healthy control group [0.18 (0.01, 0.25)% vs. 3.40 (0.46, 5.78)%, 0.01 (< 0.01, 0.29)% vs. 2.26 (0.84, 4.86)%, 0.01 (< 0.01, 0.02)% vs. 2.73 (1.87, 5.74)%, 0.02 (< 0.01, 0.07)% vs. 0.80 (0.50, 2.32)%, < 0.01 (< 0.01, < 0.01)% vs. 0.88 (0.33, 2.08)%, 0.02 (< 0.01, 0.31)% vs. 7.74 (0.07, 36.27)%, all P < 0.05]; the proportions of Escherichia and Enterococcus in the severe pneumonia group were higher than those in healthy control group, but there was no difference between the two groups [2.00 (0.57, 10.23)% vs. 1.16 (0.23, 2.68)%, 0.02 (< 0.01, 0.42)% vs. < 0.01 (< 0.01, 0.04)%, both P > 0.05]; the proportions of Fusobacterium and Staphylococcus in severe pneumonia group were significantly higher than those in healthy control group [0.01 (< 0.01, 0.08)% vs. < 0.01 (< 0.01, < 0.01)%, 0.01 (< 0.01, 0.02)% vs. < 0.01 (< 0.01, < 0.01)%, both P < 0.05].

Gut microbiota dysbiosis in patients with severe pneumonia shows that the abundance and diversity decrease, structure of intestinal flora changes, and beneficial symbiotic bacteria decrease and pathogenic bacteria increase, which may be associated with the occurrence and development of severe pneumonia.