Figure 3. ABUW_1645 is a global regulator in mediating phenotypic switching, virulence and resistance to host defenses.

(a), Representative colonies of VIR-O or AV-T cells overexpressing ABUW_1645 or with empty vector. (b), VIR-O/vector (red) and VIR-O/1645 (green) were treated with lysozyme, H₂O₂ or CRAMP, and percent survival relative to VIR-O/vector was calculated. The reported values represent the mean of three independent replicates with standard deviations. Repeated experiments gave similar results. (c, d), Mice were infected with VIR-O/vector (red), AV-T/vector (blue), VIR-O/1645 (green) or AV-T/1645 (gold) strains (10 mice/group). At 24 hours post-infection, lungs were harvested and plated for colony forming units (d) and assessed for the percentage of VIR-O and AV-T cells present (c). (e), Survival of mice infected with VIR-O/vector and VIR-O/1645 (n=5/group). This experiment was repeated two times with identical results. (f), Survival of VIR-O/1645 and E. coli-vaccinated mice after lethal challenge (n=5/group). This experiment was repeated two times with identical results. (g) Blood cultures from A. baumannii-infected patients were plated directly on 0.5× LB agar plates to assess the percentage of VIR-O and AV-T cells present. (h) For each isolate, AV-T variants were isolated from the VIR-O colonies and the expression of ABUW_1645 was determined in each variant by quantitative real-time PCR. Data represents the mean from three replicates and error bars represent standard deviations of the mean. Student’s two-tailed t-test (*p < 0.05; **p <0.005; ***p < 0.0005) was used in (b and h). A two-tailed Mann-Whitney test was used in (d)(***p < 0.0005). ns, not significant.