Imaging of bioluminescent Klebsiella pneumoniae induced pulmonary infection in an immunosuppressed mouse model

OBJECTIVE: To establish a mouse model of bioluminescent Klebsiella pneumoniae-induced lung infection, under different infection states after pretreatment with various dosages of cyclophosphamide (CTX). METHODS: A K. pneumoniae strain carrying the luxCDABE operon was used to infect immunocompetent mice (intraperitoneal injection of saline at 4 days and 1 day prior to experimental lung infection) and immunodeficient mice (50 mg/kg CTX at 4 days and 50 mg/kg CTX at 1 day prior to lung infection; or 150 mg/kg CTX at 4 days and 100 mg/kg CTX at 1 day prior to lung infection). Disease progression was monitored in living mice using a bioluminescence imaging system. The bioluminescent images, bacterial loads in lungs, blood cytological changes and histopathology of lungs were analysed. RESULTS: K. pneumoniae-induced lung infection models were established in mice pretreated with CTX. Different doses of CTX led to different severities of lung infection. Mice pretreated with 150/100 mg/kg CTX were more suitable for real-time monitoring as they had more typical bioluminescent images of lung infection, more obvious changes in the bioluminescent intensity values, more bacterial colonies in the lungs and more distinct pulmonary pathological changes. CONCLUSIONS: A stable bioluminescent K. pneumonia-induced lung infection model was successfully established in mice pretreated with CTX, which can be semi-quantitatively monitored in real-time.