1. The bacterial flora of the respiratory sputum specimens of the healthy medical staff and the tuberculosis patients were diverse, with five main phyla: Proteus, Firmicutes, Fusobacterium, Actinomycetes and Bacteroides.
Among the 10,713,472 raw 16S rRNA readings obtained, 5,090,698 raw Reads were from the TB group samples, and 5,622,774 raw Reads were from H group samples. 3,783,786 clean Reads in TB group were obtained by filtering process, which removed 25.67% of original sequence Reads. For H group, 4,138,850 clean Reads were retained and 26.39% original sequence Reads were deleted. After removing the primer sequence, the average length is about 252 bp. The clean Reads were spliced into Tags through the overlap relationship between the reads, and each sample retained 67,519 tags on average. Finally, 600 OTUs were obtained. The TB group had 168 OTUs, and the H group had 70 OTUs. The two groups had 362 shared OTUs. All OTUs used Greengenes comparison to obtain the five main bacterial phyla: Proteus, Firmicutes, Fusobacterium, Actinomycetes and Bacteroides. Other bacteria were also detected, such as TM7, Spirochace, SR1, Cyanobacteria, and Tenericutes, which together accounted for < 4% of the total readings analyzed.
2. The TB group had significant difference from the H group in both Alpha and Beta diversity. However, there was no significant difference in Alpha and Beta diversity between DS0 group and DR0 group.
By phylogenetic-based weighting (Unifrac distance metric), the PcoA principal coordinate analysis between samples in different groups was generated, showing that tuberculosis samples (TB) and samples from health controls (H) have different clusters (Fig. 1). Shannon diversity Kruskal-Wallis Test was used to analyze the differences between the drug-sensitive (DS0) group, drug-resistant (DR0) group and H group. The median values were 2.63, 2.34 and 3.08, respectively, P < 0.001. There were statistical differences between DS0, DR0 and H, and the diversity in the samples of TB patients in the above two groups was lower than that of H (Fig. 2). Beta diversity cluster analysis was conducted for samples from the DS0, DR0 and H groups based on the distance between samples, and the median values were 0.56, 0.58 and 0.30, respectively, P < 0.001, indicating that there was a statistical difference between DS0, DR0 and H (Fig. 3). The inter-individual diversity of samples from TB patients in the above two groups was higher than that of H. There is no significant difference on both Alpha diversity and Beta diversity between DS0 group and DR0 group (P > 0.05).
3. There were differences in the relative abundance of species between the tuberculosis and healthy respiratory samples.
60 samples were sequenced and clustered into 600 OTUs by 16S rRNA amplicon. Greengenes annotation was used to identify Actinobacteria, Fusobacteria, Bacteroidetes, Proteobacteria and Firmicutes as five main phyla. The dominant phyla were Proteobacteria and Firmicutes. The corresponding dominant bacteria genera were Neisseria, Haemophilus, Streptococcus and Veillonella. In addition, the main genus of Fusobacteria is Fusobacteriales, while the main genus of Bacteroidetes is Prevotella (Fig. 4). On the level of genus, the top 15 species in abundance were Actinobacillus, Campylobacter, Capnocytophaga, Lautropia, Actinomyces, Granulicatella, Rothia, Fusobacterium, Leptotrichia, Porphyromonas, Haemophilus, Veillonella, Streptococcus, Neisseria and Prevotella (Fig. 5).
In phylum level, the relative abundance of Proteobacteria (25.89% vs 36.69%), Fusobacteria (4.76% vs 9.51%), TM7 (0.96% vs 1.75%), Spirochaetes (0.07% vs 0.56%), SR1 (0.18% vs 0.34%), Tenericutes (0.06% vs 0.16%) in TB group was lower than H group (P < 0.05) and the relative abundance of Firmicutes (40.30% vs 26.75%) and Actinobactria (6.30% vs 2.95%) in TB group was higher than H group (P < 0.05) (Fig. 6).
The relative abundance of the first 15 bacterial genera in sputum samples of the TB and H groups (Fig. 5), and the differences of key species are shown in Fig. 7. The Relative Abundance of Neisseria, Haemophilus, Porphyromonas, Fusobacterium and Granulicatella were different. The Relative Abundance of the first 4 genera of bacteria in the above two groups were 17.23% and 20.40%, 4.61% and 10.70%, 2.71% and 4.43%,1.65% and 6.74%, respectively. Wilcox rank sum test showed that the p-values were 0.04, 0, 0.001, 0, respectively, which indicated that the genera mentioned above in TB group was lower than that in H group. However, Granulicatella in TB group is higher than H group: 3.94% and 0.74%, p-value was 0.03. At the species level, the relative abundance of Veillonella dispar was 10.82% and 3.75% higher than that of H, and the p-value was 0.01. Neisseria subflava, Haemophilus parainfluenzae, Prevotella pallens and Prevotella nanceiensis were lower in TB than in H (P < 0.05).
4. There were differences in the distribution of bacteria in the drug-sensitive group (DS0) and drug-resistant group (DR0)
There were differences in the relative abundance of DS0 and DR0 (Fig. 8). The Streptococcus relative abundance of DS0 group is higher than that of DR0 group :25.35% and 12.41, mainly reflected in the species level of Streptococcus infantis, P < 0.05, showing statistical difference.