(A) Antimicrobial susceptibility of the K. pneumoniae strains isolated from the airway and bloodstream of a patient over a 3-month hospitalization. B, blood; T, tracheal aspirate. Red = resistant, Yellow = intermediate, or Green = sensitive minimum inhibitory concentration for the given isolate for the corresponding antibiotic. (B) Kinetics of KP35 clearance from bronchoalveolar lavage fluid (BALF), lung homogenate, and spleen following intranasal inoculation of 1 × 10⁸ to 2 × 10⁸ CFU in WT mice over the course of a 4-day infection. # = the lower limit of detection. Horizontal lines represent median values and each data point represents an individual mouse. n = 6 per time point. All data were compiled from 2 independent experiments. n = 5–6 per time point. *P < 0.05, compared with CFU at 4 hours of infection, Kruskal-Wallis test, 1-way ANOVA, Dunn’s correction for multiple comparisons. (C) Weight loss over the course of infection, data points represent mean values ± SEM. n = 5–6 per time point. (D) Bacterial load enumerated from selected compartments after 7 days of infection. # = the lower limit of detection. Horizontal lines represent median values and each data point represents an individual mouse. n = 4–6 per compartment. (E) CT imaging demonstrates diffuse bronchopneumonia 48 hours following KP35 infection. Representative axial images obtained with the Quantum FX CT Scanner in 3-μm slices are shown. (F) Histopathology of KP35 pneumonia demonstrating peribronchial consolidation and cellular infiltrates in H&E-stained sections of lung, PBS control, and KP35 infection at 48 and 96 hours. (G) Trichrome staining of KP35-infected lung sections demonstrating patchy disruption of the alveolar architecture and discrete areas of collagen deposition. Scale bars (F and G): 100 μm.