Fig. 1: Pathological, inflammatory cytokines, viral load and bacterial burden analysis of IAV and MRSA co-infection mice.
A Establishment of the single pathogen infection or co-infection model. Briefly, four-week-old C57BL/6 mice were infected with 0.2 LD50 IAV and then coinfected with 40 μL 107 CFU/mL MRSA 3 days later. Control groups were only infected with single pathogen. B Survival curve of C57BL/6 mice infected with IAV and MRSA or separately (n = 13). C Weight changes of C57BL/6 mice infected with IAV and MRSA or separately (n = 13). Body weight changes are normalized to the average body weight in each group on the first day and multiply by 100%. D Lung index was calculated in the control and infectious groups (n = 5). Lung index = lung weight of mice (mg)/body weight of mice (g). E Representative pathological images (Scale bars: 200 μm) of lung tissue in different groups. Stain areas of images were calculated using image j and then normalized to the average area of the 0.2 LD50 IAV infection group (n = 3). F Inflammatory cytokines IL-1β and IL-6 mRNA levels were measured by qRT-PCR (n = 5). Data are normalized to β-actin and presented as fold of gene expression in the infected groups compared to the control. G Viral load of IAV was determined by analysis of influenza virus M gene copy (n = 5). Bacterial burden was determined by spreading 5 μL of the lung homogenates on the selective S. aureus medium (n = 5). Data are mean ± standard error of the mean (*p < 0.05; **p < 0.01; ***p < 0.001). IAV Influenza virus; MRSA methicillin-resistant S. aureus.
