[Presence of Pneumocystis carinii and Pneumocystis wakefieldiae DNA in the extrapulmonary tissues of immunocompromised laboratory rats].

Fungi of the genus Pneumocystis are opportunistic pathogens which cause lethal pneumonia in immunocompromised hosts. Those fungi may also invade other visceral organs where they induce lesions, although, the pathways or mechanisms of the in vivo infection are still unknown. The corticosteroid-treated rat model was used to evaluate the course of extrapulmonary pneumocystosis. Liver, kidney, spleen, and mesenteric lymph nodes of 16 rats were examined for the presence of mtLSU gene fragments of P. carinii and P. wakefieldiae using the nested PCR method. Pneumocystis DNA was detected in 26 organ samples of which 17 contained both species (P. carinii and P. wakefieldiae) and 9 contained only P. carinii. Positive samples were received from 10 rats examined after 6-9 weeks of immunosuppression. The highest percentage of positive samples (62.5%) was obtained among examined visceral lymph nodes. Pneumocystis DNA was detected in the blood serum of two rats with no traces of the DNA in their internal organs. Conversely, Pneumocystis DNA was found in the internal organs of two other rats, although their serum samples were negative. The average number of Pneumocystis cysts in the lungs of animals in which extrapulmonary infection was detected was 3.4 per one microscopic view field. In the case of animals where the infection was limited to the lung tissue this number was almost two times lower (1.8 cysts per one microscopic view field). An analysis of the results of the presently reported experiment showed that massive Pneumocystis infection in the lungs makes it more likely that Pneumocystis will spread to other internal organs. This spread probably takes place via the lymphatic vessels. The extrapulmonary foci may contain either P. carinii alone, or both pathogens: P. carinii and P. wakefieldiae.