Environmental monitoring for Aspergillus fumigatus in association with an immunosuppressed rabbit model of pulmonary aspergillosis

Aspergillus fumigatus causes life-threatening pneumonia in immunocompromised patients. Conidia, the infectious form of the organism, are handled in a biologic safety cabinet under BSL2 conditions. However because germinated conidia form noninfectious hyphae in tissue, we hypothesized that rabbits inoculated intratracheally would grow A. fumigatus in their lungs but that the environment would remain free of this fungus, potentially permitting maintenance of infected animals under ABSL1 conditions. We performed a surveillance study for the presence of A. fumigatus in the environment before proceeding with antifungal therapy studies of experimental pulmonary aspergillosis. The expected outcome included absence of A. fumigatus in the environment, stool, and blood and presence in rabbit lungs. Female SPF New Zealand white rabbits were immunosuppressed and inoculated intratracheally (n = 4) or intraesophageally (n = 2) with 1.25 × 10⁸ conidia of A. fumigatus. Feces, pan liners, and walls were sampled daily during the 11-d experiment, and blood was sampled on days 2, 6, and 8 after inoculation. Samples were cultured on 5% Sabouraud glucose agar plates. Lungs were weighed and scored for hemorrhagic infarcts and homogenized for culture on 5% Sabouraud glucose agar and trypticase soy agar plates. Blood cultures, rabbit stool, and environmental swabs were all negative for A. fumigatus whereas the lungs inoculated intratracheally demonstrated 4.5 × 10² ± 0.8 × 10² CFU/g of A. fumigatus. Therefore, neutropenic rabbits with experimental invasive pulmonary aspergillosis do not shed conidia of A. fumigatus and can be safely housed under ABSL1 conditions after inoculation.