Figure 7
AutA and AutR contributed to DE205B phenotype fitness for intracellular survival, serum resistance, colonization in duck lungs and sepsis in vivo.
(A) DE205BΔautA and DE205BΔautR decreased its adherence on DF-1 cells for 2 h and 4 h post-infection compared with the control strains DE205B and DE205BΔupaB. Statistical significance analysis was performed using one-way ANOVA (*P < 0.01). (B) The autA and autR mutants enhanced its intracellular survival within HD11 cells compared with the control strains DE205B and DE205BΔupaB in vitro, as fold change in bacterial number at time points (4 h, 6 h, 8 h and 16 h) relative to initial number of intracellular bacteria for 2 h. The two-way ANOVA was performed for survival assays (*P < 0.05). (C) To determine the effect of autA and autR loss on APEC virulence for duck model. The autA and autR mutants enhanced the survival/mortality rates compared with the control strains DE205B and DE205BΔupaB (*P < 0.01). (D) The systemic infection experiment was conducted to assess the bacteria proliferation in duck lungs and blood. DE205BΔautA, DE205BΔautR and DE205BΔautA/autR enhanced the colonization in lungs and proliferation in the blood compared with the control strains DE205B and DE205BΔupaB. A nonparametric Mann-Whitney U test was performed for statistical significance analysis (*P < 0.01). (E) Bactericidal assays revealed that the autA and autR mutants had higher resistance to non-infected duck serum compared to the control strains DE205B and DE205BΔupaB. Bacteria were incubated with the normal duck serum for dilution (1:10 or 1:2) at 37 °C. Statistical significance analysis was performed using one-way ANOVA (*P < 0.01)
