Fig. 1From: Influenza infection elicits an expansion of gut population of endogenous Bifidobacterium animalis which protects mice against infectionThe heterogeneity of mouse response to influenza infection is closely associated with the gut microbiota. a, b SPF C57BL/6 mice were intranasally infected with a LD50 dose of the virulent H7N9 virus strain GX (n = 30, 50 μL/mouse), the same dose of the attenuated H7N9 virus strain HB (n = 10, 50 μL/mouse), or were administered an equal volume of PBS (NC group) (n = 10, 50 μL/mouse). a Mouse survival rate. b Mouse weight loss. Based on survivability, the GX-infected mice were divided into a group that survived the infection (GX.SG) and a group that succumbed to the infection (GX.DG). The data are presented as the mean ± SD. c H&E staining of the mouse lung. The mice were sacrificed on day 10 post-infection of another repeat experiment, and the lungs were collected. The mice in the GX group that succumbed to the infection comprised the GX.DG group (n = 3), and the mice in the GX group that started to show improvement were defined as the GX.SG group (n = 3), as well as the HB group (n = 3) and NC group (n = 3). Representative images are shown. d Experimental setup for FMT experiments. Fecal microbes were collected on days 3 and 9 after GX infection (n = 20) and were divided into the GX.SG (n = 10) and GX.DG (n = 10) groups based on whether the mice from which the samples were collected succumbed to or survived the infection. SPF mice that had been treated with an antibiotic solution (ATB) for 3 days underwent FMT of the fecal microbes, as indicated. One day after FMT, the mice were infected with a LD50 dose of GX. e, f The survival of GX infection by mice after FMT of feces from GX-infected mice obtained on days 3 (e) or 9 (f) after the infection or feces from NC mice; survival of mice administered PBS before GX infection is shown as a control (n = 20 mice per group). Statistics in survival assay were done with the log-rank (Mantel-Cox). All experiments were performed at least twice under similar conditions and yielded similar resultsBack to article page