Experimental blastomycosis pneumonia in mice by infection with conidia.

We describe a murine model of acute blastomycosis pneumonia induced by Blastomyces dermatitidis conidia. Anesthetized mice were infected by placing a droplet containing conidia suspended in sterile saline on the nares and allowing the suspension to be aspirated into the lungs. Conidia were obtained from mycelia derived from the yeast forms of two well characterized strains of B. dermatitidis, ATCC 26199 and 26197. ATCC 26199 yeast and conidia were highly virulent in BALB/cByJ mice whereas both forms of ATCC 26197 were incapable of causing disease in 60 days. Conidia and yeasts of the virulent strain caused pathologic changes primarily in the lungs, whereas no abnormalities were seen in the lungs, or elsewhere, in mice infected with the a virulent strain. Small numbers of ATCC 26199 yeast forms were found in scattered foci in liver and kidneys, but no inflammatory reaction surrounded the fungus. This murine model of acute blastomycosis pneumonia mimics the acute disease in humans and is initiated with the naturally infectious particle.