<prompt> A patient presents to the emergency depament with history of persistent fever cough. Radiological features are suggestive of pneumonia. Sputum examination cultures reveal aerobic branching Gram positive filaments that are paially acid fast.Which of the following is the most likely etiological agent -Actinomyces israeliNocardia asteriodesAspergillus fumigatusStaphylococcus aureus  <response>: Ans. is b i.e., Nocardia asteroides . Information in this question are :? i Aerobic organism. ii Branching filament. iii Gram positive iv Paially acid fast v Patient has pneumonia Among the given options only Nocardia asteroides is acid fast. Nocardia is strict aerobe, acid fast, Gram positive and branching beaded filamentous. Most common clinical manifestation of Nocardia is pneumonia. 