A HIV patient with CD4 count of 160 cells/ul presented with fever, cough and shoness of breath for 3 weeks. Chest X ray is shown below. Based on the x ray findings silver staining of the bronchoalveolar lavage was done and shown below. What is drug of choice for the causative organism?

Chest X ray depicts bilateral widespread interstitial pneumonia and Gomori Methenamine silver staining shows cysts with crushed ping pong balls appearance and are present in aggregate of 2-8. This is characteristic of Pneumocystis Pneumonia which is typically seen in AIDS patient in which CD4 cell count is below 200cells/ul Treatment:Double strength Cotrimoxazole i.e. Trimethoprim160mg + sulfamethoxazole800mg (continued till CD4 count is more than 200cells/ul.)