Fig. 4

Administration of EB211 and EB279 prevented severe tissue damage in the liver of immunocompromised mice with A. baumannii pneumonia. Immunocompromised mice were inoculated intranasally with XDR A. baumannii A.b.56 at a 50% lethal dose (LD₅₀; 4×10⁷ CFU per mouse). Immunocompromised infected mice were administered intraperitoneally twice daily with EB211 (12 mg/kg), EB279 (12 mg/kg), a cocktail of the two scFvs (CKT; 6 mg/kg of each), an irrelevant scFv (MEH158; an S. aureus-specific scFv) (12 mg/kg), colistimethate sodium (CMS; 30 mg/kg), or normal saline (NS), or once daily with EB211 (12 mg/kg) (Q24H) two hours after inoculation for 72 h. Healthy (H), immunocompromised uninfected (IU), and immunocompromised infected (Iinf) mice were killed at 72 h of infection, and the liver were collected. Tissue sections were stained with hematoxylin-eosin and microscopically evaluated for histopathological alterations. Bacterial communities and infiltration of inflammatory cells (neutrophils and mononuclear cells) along with spotty necrosis‌ were observed in the liver of Iinf mice treated twice daily with NS or MEH158. After 72 h of infection, no severe pathological signs were detected in the liver of Iinf mice treated twice daily with EB211, EB279, or CKT for 72 h. Black arrows: bacterial foci, Black arrowheads: necrosis of hepatocytes, Red arrowheads: bi-nucleated cells, White arrows: infiltration of inflammatory cells (mononuclear cells) along with spotty necrosis, White arrowheads: micro and macro vesicles