CHARACTERIZATION OF NATURAL OCCURRING PNEUMOCYSTIS-CARINII PNEUMONIA IN PIGS BY HISTOPATHOLOGY, ELECTRON-MICROSCOPY, IN-SITU HYBRIDIZATION AND PCR AMPLIFICATION

Macroscopic, histologic, ultrastructural, microbiologic, in situ hybri dization (ISH) and PCR detection results in three 8-week-old pigs natu rally infected with Pneumocystis carinii (PC) are described. All anima ls had a nonsuppurative interstitial pneumonia and intra-alveolar Pneu mocystis organisms with foamy eosinophilic and PAS positive appearance . Ultrastructurally, PC trophozoites and cysts were observed in pigs N o. 2 and No. 3, with the former being much more numerous. PC organisms were located on the alveolar surface or within the alveolar septa. Tr ophozoites had numerous-filopodia and were thin-walled. Cysts had no o r few filopodia, were thick-walled and contained intracystic bodies. U sing non-isotopic ISH on formalin-fixed, paraffin-embedded lung tissue sections, PC DNA from pigs No. 2 and No. 3 hybridized with a probe sp ecific for PC ribosomal PNA (rRNA). Using primers specific for mitocho ndrial rRNA gene (pAZ102-E/pAZ102-H), and for the internal transcriber spacers of ribosomal gene of PC, PCR methods amplified a product in t he lung of pigs No. 2 and No. 3 using either frozen or formalin-fixed and paraffin-embedded lung tissue. DNA from Pig No. 1 samples did not amplify with any primer. This is the first time that molecular biology techniques (in situ hybridization and PCR) have been applied to the s tudy of porcine pneumocystosis.