<prompt> P. Carni causes infection of primarily -RatsMiceHumansRabbits  <response>: Ans. is a i.e., Rats Ref: Harrison 18the p. 1671 I7the p. 1267o Although the organisms within the pneumocystis genus are morphologically very similar, they are genetically diverse and host specific - P. jirovecii infects humans, where as P.carinii infects rats.Pneumocystis jirovcci P. cariniio Pneumocystis is an opportunistic fungal pulmonary pathogen,o Developmental stages1. Pleomorphic trophic form2. Thick walled cyst3. Precyst - an intermediate stageo Risk factors1. HIV CD4 T cell 200 mL3. Primary immunodeficiency diseases2. Immunosuppressive therapy particularly glucocorticoids4. Premature malnourished infants.Clinical features of P. carinii pneumonia Dyspnea Non productive cough Tachycardia Fever Tachypnea CynosisExtrapulmonary spreadCommon in patients with HIV to whom aerosolized pentamidine has been administered.Sites of involvement are:o Lymph nodeso Bone marrowo Livero Spleeno Eye choroiditis Chest X-rayBilateral diffuse infiltrates beginning in the peri hilar regions - classical finding.Upper lobe infiltrates - who receive aerosolized pentamidine.Pneumothorax.o Hypoxemia is most widely used prognostic factor for P. carinii pneumonia. 