P. Carni causes infection of primarily -

Ans. is 'a' i.e., Rats [Ref: Harrison 18th/e p. 1671 & I7th/e p. 1267}o 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. carinii)o 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 mL)3. Primary immunodeficiency diseases2. Immunosuppressive therapy (particularly glucocorticoids)4. 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.