New rat model of Pneumocystis carinii infection.

Rats free of latent Pneumocystis carinii organisms were immunosuppressed with adrenal corticosteroids and transtracheally injected with P. carinii. These animals subsequently developed P. carinii pneumonia. Infection was accomplished by using organisms from infected rat lung or from culture. Diffuse infection was produced with no significant differences in the numbers of organisms found in various lobes of the lungs. Infections progressed over time so that by 6 weeks postinoculation all animals were heavily infected. Infection by transtracheal injection has three advantages over current models. First, transtracheal injection provides a reliable model which is not dependent on naturally occurring latent Pneumocystis infection. Second, transtracheal injection allows the perpetuation of specific Pneumocystis strains. Third, transtracheal injection is a more rapid and economical means of producing severe Pneumocystis pneumonia.