In vivo imaging of rat experimental invasive pulmonary aspergillosis using fibred confocal fluorescence microscopy

Rational: Aspergillus fumigatus is responsible for life-threatening respiratory infections in immunosuppressed patients. Early diagnostic would improve the prognosis. Fibred confocal fluorescence microscopy (FCFM) is a new endoscopic tool that enables in vivo microscopic imaging of the distal lung in situ . In this study we tested the hypothesis that FCFM could be utilized for the visualization of pulmonary aspergillosis infection in vivo, in situ . Methods: Experimental pulmonary invasive fungal infections were induced in immunosuppressed rats using a wild strain of A.fumigatus (n=6) a wild strain of Geosmithia argilacea (n=6) and a fluorescent transformed Tag-RFP A.Fumigatus strain (n=6). Subpleural areas of pulmonary infection and control lungs were imaged in vivo using FCFM through a chest wall window. Results: From the fungal strains, only hyphae of the Tag-RFP A.fumigatus were detectable by FCFM both in vitro and in vivo . In vivo , hyphae of the Tag-RFP Aspergillus strain were visualized by FCFM in 100% of the lung infection with a specificity of 100% (6/6) compared to normal lung and other fungal infection. Using non fluorescent strains, a specific local infiltration of fluorescent cells could be localized in half fungal subpleural microabcesses (Se 100%;Spe 58%). Conclusion: FCFM represents the first imaging technique of pulmonary aspergillosis in real time and in vivo . It provides a new tool to study host-pathogen interactions and may help for early diagnosis of pulmonary aspergillosis in vivo .