Effect of etoposide and cyclophosphamide on an experimental pulmonary infection in mice

The effects of monocytopenia and granulocytopenia on the proliferation of Klebsiella pneumoniae and the efficacy of treatment with ceftriaxone were studied in an experimental lung infection in mice. Treatment with etoposide led to monocytopenia, and cyclophosphamide to granulocytopenia and monocytopenia. Both drugs gave a decrease in the number of alveolar macrophages during the infection and a diminished influx of granulocytes into the alveolar space. The mice treated with etoposide did not differ from controls with respect to either the proliferation of Kl. pneumoniae during the infection or the antibiotic efficacy of ceftriaxone. In cyclophosphamide-treated mice the proliferation rate of Kl. pneumoniae was higher than that in the control mice and a higher dose of ceftriaxone was needed to reduce the number of bacteria to the level in the controls. From these findings it is concluded that granulocytes play an important role in the numerical reduction of Kl. pneumoniae and that monocytes make no contribution to infection control in this model.