# DBT JRF 2022 — Question 50

Exam: DBT JRF 2022 · Section: B · Topic: Microbiology › Obligate Intracellular Parasites · Difficulty: Medium

## Question

Which one of the following organisms is NOT an obligate intracellular parasite and, therefore, can grow on bacteriological media?

## Options

- **A.** Mycoplasma
- **B.** Chlamydia
- **C.** Rickettsia
- **D.** Adenovirus

## Answer

Option A

## Explanation

Mycoplasma vs. obligate intracellular organisms — culture on bacteriological media: Mycoplasma: • Wall-less bacteria (smallest self-replicating organisms) • CAN grow on specialised bacteriological media: PPLO (Pleuropneumonia-Like Organism) broth and agar, enriched with cholesterol, serum, and yeast extract. • Forms characteristic 'fried egg' colonies on solid media. Obligate intracellular pathogens (CANNOT grow on bacteriological media): • Chlamydia trachomatis: infects epithelial cells; requires cell culture (HeLa, McCoy cells) or embryonated eggs. • Rickettsia: requires living cells for growth; L929 or Vero cell lines. • Adenovirus: a DNA virus; must grow in permissive eukaryotic cells; cannot grow on any bacteriological medium. Answer: Mycoplasma can grow on specialised bacteriological media; the others cannot.

Source: https://mypyqbuddy.com/questions/which-one-of-the-following-organisms-is-not-6a104cd5920734408bc0c741