Neisseria meningitidis appears as which of the following under the microscope?

• A. Gram-negative diplococci
• B. Gram-positive rods
• C. Gram-positive cocci in clusters
• D. Gram-negative spirilla

Answer: (A)

Verified step by step guidance

1. Recall the Gram stain characteristics of Neisseria meningitidis. It is known to be a Gram-negative bacterium, which means it does not retain the crystal violet stain and appears pink or red under the microscope after Gram staining.
2. Understand the shape and arrangement of Neisseria meningitidis cells. This bacterium typically appears as cocci (spherical-shaped bacteria) arranged in pairs, which is described as diplococci.
3. Compare the options given: Gram-positive rods are rod-shaped and stain purple, Gram-positive cocci in clusters are spherical and stain purple, Gram-negative spirilla are spiral-shaped and stain pink.
4. Since Neisseria meningitidis is Gram-negative and appears as diplococci, the correct microscopic appearance is Gram-negative diplococci.
5. Therefore, the answer is the option that describes Gram-negative diplococci, matching both the staining and morphology characteristics of Neisseria meningitidis.