Which organism (s) is/are acid-fast? A. Nocardia B. Pseudomonas C. E. coli D. Mycobacterium E. Nocardia AND Mycobacterium

E. Nocardia AND Mycobacterium

Explanation:

Acid fast organisms are not able to take up acid based stains like gram stain. They can be bacteria or eukaryotic organisms. Mechanism for acid fastness is different for each species. The most well understood mechanism is by the tuberculosis causing bacteria Mycobacterium which has high mycolic acid content in their cell wall which leads to poor absorption of dye. Nocardia is partially acid fast. Thus for identification of acid fast organisms other stains like Ziehl-Neelsen stain are used. It stains the organism bright red in blue background.