Preliminary investigation of a mice model of Klebsiella pneumoniae subsp. ozaenae induced pneumonia.

In the present study, we comparatively assessed the pathophysiological mechanisms developed during lung infection of BALB/C female mice infected by an original wild type Klebsiella pneumoniae subsp. ozaenae strain (CH137) or by a referent subspecies K. pneumoniae. subsp. pneumoniae strain (ATCC10031). The mice infected with 2.10⁶ CFU K. p. subsp. pneumoniae (n = 10) showed transient signs of infection and all of them recovered. All of those infected with 1.10⁶ CFU K. p. subsp. ozaenae (n = 10) developed pneumonia within 24 h and died between 48 and 72 h. Few macrophages, numerous polymorphonuclear cells and lymphocytes were observed in their lungs in opposite to K. p. subsp. pneumoniae. In bronchoalveolar lavage, a significant increase in MIP-2, IL-6, KC and MCP-1 levels was only observed in K. p. subsp. ozaenae infected mice whereas high levels of TNF-α were evidenced with the two subspecies. Our findings indicated a lethal effect of a wild type K. p. subsp. ozaenae strain by acute pneumonia reflecting an insufficient alveolar macrophage response. This model might be of a major interest to comparatively explore the pathogenicity of K. p. subsp ozaenae strains and to further explore the physiopathological mechanisms of gram-negative bacteria induced human pneumonia.