Fig. 4

Patients with low CD4 counts exhibit a greater degree of gut–airway microbiota similarity, loss of gut microbiota commensals, and evidence of Streptococcus and Veillonella enrichment in both gut and airway microbiota. a Patients with low CD4 counts are significantly more likely to have low airway–gut microbiota paired distance (quartile 1 versus 4 for each factor, Fisher’s exact test, p < 0.001). b CD4 low (versus high) patient stool bacterial communities exhibit enrichment of Streptococcus and Megasphaera, which are also enriched in paired airway microbiota (highlighted in green text), and depletion of microbial genera typically associated with health. Mean differences in reads/sample are plotted for the top differentiating taxa (genus-level identity provided). Significance was set at a false discovery rate q < 0.05, read difference ≥ 100 reads, and presence in ≥ 50% of the enriched group. OTU, operational taxonomic unit