This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
Nocardia is differentiated from Actinomyces by ? 
Select and explain. 
A. Gram stain, B. ZN stain, C. Nocardia causes mycetoma, Actinomyces does not, D. Nocardia is faculative anerobe
B: ZN stain
Answer: B: ZN stain 
Explanation: Ans. is 'b' i.e. Z.N. Stain Differences between Actinomyces and Nocardia Actinomyces Nocardia . Anaerobic or microaeroph i I ic . Non-acid fast . Strict aerobe . Acid fast (N. astroides and N. brasilensis) . Natural habitat mouth, . Natural habitat -- Soil intestine, vagina . Most infections are endogenous . Most infections are exogenous . Grows at 35 - 37degC . Can grow at wide range of temperature . Causes Actinomycosis . Causes Nocardiasis . Can occur with normal host . More common with deficient CMI immunity . T/t --> Penicillin . T/t ---> Sulfonamide . Nocardia is acid fast, can be differentiated from Actinomyces by Ziehl Neelsen (Z.N.) stain. . Both can cause actinomycetoma. . Both are gram positive so can not be differentiated by Gram stain.