<prompt> A 36 years male presented with complain of productive cough and fever for last 2 months. Hehas undergone kidney transplantation 2 years back. His sputum examination revealed a grampositive filamentous bacteria that showed acid fastness with modified Ziehi-Neelsen staining1 H2S04. The most likely etiological agent is ?Actinomyces israeliiNocardia asteroidesBlastomyces dermaiiidisCrfptospcridium parvum  <response>: Ans. is b i.e., Nocardia asterordes Ref: Previous explanationo Symptoms of pneumonia by a filamentous acid fast bacterium suggest the diagnosis of Nocardia.NOCARDIAMorphologyo Grant positiveo Acid fast N. astroides and N. brasiliensiso Crooked, branching, beaded, filamentous.Cultureo Use paraffin as a carbon source.o Paraffin baiting is used for isolation.o Strict aerobeo They take 2 weeks to appear and show their characteristic appearance at about 4 weeks.Clinical manifestationTreatment Sulfonamide -Drug of choice Cotrimoxazole-Equivalent Minocycline-Best alternative Amikacin-DOC for parenteral useRemembero N. asteroides is the species most commonly associated with invasive disease. 