Objective  The aim of this study was to investigate the difference in the diversity of intestinalmicrobiota of psoriasis patients compared with that of healthy people.

  Methods  Fresh fecal samples and clinical data of hospitalized psoriasis patients from May 2017 to June 2018 in the Institute of Dermatology of Chinese Academy of Medical Sciences & Peking Union Medical College were prospectively collected. Healthy people undergoing physical examination during the same period were selected as the healthy control. After DNA extraction of intestinal microbiota and the gene amplification of 16S rDNA, the paired-end 2×300 strategy was used to sequence by Illumina platform. According to Gold database and the similarity-clustering operational taxonomic unit (OUT) > 97%, intestinal microbiota was annotated and classified by Silva database. The species difference of samples at all levels was analyzed using Rank sum test. The main index of α diversity and the analysis of β diversity were calculated using QIIME software. All indexes were analyzed by Welch's t test and P < 0.05 was considered statistically significant. The results were shown by R and GraphPad Prism plotting.

  Results  Totally 11 psoriasis patients and 21 healthy controls were eligible for this study. Between the psoriasis group and the healthy group, the ratios of gender, age, and body mass index showed no statistical significance (all P > 0.05). The DNA sequencing showed that coverage index of samples' sequencing was > 0.99. The OTU numbers (278.18±89.75 vs. 722.95±152.81, t=10.36, P < 0.01), Zhao index (433.38±147.47 vs. 1156.08±292.50, t=9.291, P < 0.01), Shannon index (3.56±0.87 vs. 5.73±0.78, t=6.972, P < 0.01), and Simpson index (0.79±0.15 vs. 0.94±0.04, t=3.287, P < 0.01) of the particular species of intestinal microbiota in the psoriasis group were significantly lower than those of the healthy group. The Rank-abundance curve showed that the psoriasis group had a lower evenness of intestinal microbiota. PCoA analysis (unweighted) showed that the first principal component (24.35%) was significantly separated between the two groups; however, Weighted UniFrac analysis showed that it was not clearly distinguished when the samples of the psoriasis group were mixed with the healthy group, which was independent of the subtypes of psoriasis. Through the sample clustering analysis, the intestinal microbiota partly overlapped between the two groups and the special microbiota were less in the psoriasis group. In the phylum level, TM7 could be detected in the healthy group and its relative abundance was 0.000 066 9 (0.000 033 4~0.000 200 5), while it was at micro-level in a few samples of the psoriatic group with a relative abundance of 0(Rank sum test, P < 0.05). On the genus level, the psoriasis group had significantly lower bifidobacterium0.000 033 4(0.000 016 7~0.000 100 3) vs. 0.000 401 1 (0.000 200 5~0.001 337 0), brauteria0.000 467 9 (0.000 183 8~0.000 434 5) vs. 0.002 206 0(0.000 935 9~0.005 582 0), and fecal coccus0.000 033 4 (0~0.000 401 1) vs. 0.000 902 5(0.000 334 2~0.005 315 0) compared to the healthy group. Dialisteria and haemophilus appearing in the healthy group were only found in a few samples in the psoriasis group. Klebsiella existed in a few samples of the two groups but was lower in the psoriasis group (relative abundance was close to 0) (Rank sum test, all P < 0.05). The high abundance analysis of individual samples showed that in some psoriasis samples, the abundance of the taxa related to the metabolism of polysaccharides and short-chain fatty acids was decreased.

  Conclusion  Diversity of intestinal microbiota in psoriasis patients is lower than that of healthy people.