Induction of Chronic Pneumonia in Normal Mice by Klebsiella pneumoniae

Experimental chronic pneumonia was established in normal BALB/c mice employing a virulent encapsulated strain of Klebsiella pneumoniae B5055. A single exposure to the bacterial pathogen resulted in acute pneumonia that resolved within a week. To achieve the chronic state of lung infection, repeated infection was given via intranasal route. Mice were inoculated with 50ul of 10 4 CFU/ml each on day 0, 7 and 14. There were two peaks observed in the assessment of the lung bacterial load and pro inflammatory cytokine generation following the first and the third infection, respectively. On day 18 of infection, histopathological examination revealed extensive chronic inflammatory changes in the lungs of infected mice which coincided with high lung bacterial load. Tissue damage was also assessed through analysis of malondialdehyde (MDA), lactate dehydrogenase (LDH), and nitric oxide generation in the lung homogenates of the infected mice.