Which spherical bacteria grow in pairs and cause diseases such as pneumonia?

• A. Diplococci
• B. Cocci
• C. Bacilli
• D. Staphylococci

Answer: (A)

Spherical bacteria that grow in pairs are called diplococci. This paired arrangement happens when cocci divide in one plane and stay attached, forming two connected spheres. Diplococci are classically associated with pneumonia because Streptococcus pneumoniae, a well-known pneumonia-causing organism, is a diplococcus.

If you only say “cocci,” you’re describing spherical bacteria in general, but they can appear in different patterns: chains (strep) or clusters (staph). Bacilli, on the other hand, are rod-shaped, not spherical, so they don’t fit the description. So the term that best fits bacteria that are spherical and grow in pairs, particularly linked to pneumonia, is diplococci.