Which of the following organisms does NOT react with gram's stain ?

Correct answer: C. Mycobacterium tuberculosis

  • A. Actinomyces israelii
  • B. Candida albicans
  • C. Mycobacterium tuberculosis
  • D. Streptococcus mutan

Explanation

Mycobacterium tuberculosis has a lipid-rich, mycolic-acid cell wall and is poorly stained by the Gram method, so it is identified by acid-fast staining. Actinomyces and Streptococcus are Gram-positive bacteria, while Candida can also appear Gram-positive.

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