Spectrum of pathogen- and model-specific histopathologies in mouse models of acute pneumonia
Infection of murine lungs with different bacterial or viral pathogens resulted in striking differences in the distributions, expansions and symmetries of pneumonic lesions that were highly reproducible for each pathogen. Mainly centrally located lesions induced by S. aureus and L. pneumophila remained close to the hilus with no trend towards peripheral expansion. Infection with S. pneumoniae, A. baumannii and MERS-CoV resulted in lesions closely surrounding the airways and blood vessels close to the central major airway segments with centrifugal expansion towards the periphery. In contrast, lesions induced by K. pneumoniae were mostly located in the periphery of the lobes and airways and much weaker adjacent to the hilus. Hematogenous infection with E. coli was associated with entirely diffuse distribution of lesions affecting the whole lungs with myriads of inflammatory hot spots, commonly surrounding blood vessels. IAV-induced lesions were restricted to individual lung lobes with a rather homogeneous distribution within affected lobes. Which lobes were affected followed a rather random and inconsistent pattern. Superinfection of S. pneumoniae into an IAV-pneumonia resulted in a pattern virtually identical to that seen after IAV infection alone. Except for E. coli induced pneumonia, virtually all lung lesions were distributed asymmetrically between the left and right lung halves with no tendency of either half to be more often or more strongly affected.