A 22-year-old man presents with urethral discharge and dysuria. Urethral swab culture on Eaton's agar (PPLO agar) grows tiny 'fried egg' colonies after 10 days. Gram stain shows no organisms. This pattern is consistent with infection by:
- A Neisseria gonorrhoeae
- B Mycoplasma genitalium
- C Chlamydia trachomatis
- D Ureaplasma urealyticum ✓
Explanation
Ureaplasma urealyticum (and Mycoplasma hominis) grow on PPLO (pleuropneumonia-like organisms) agar as 'fried egg' colonies due to a dense central zone and peripheral halo of surface-growing organisms. Ureaplasma differs from Mycoplasma by its urease activity (hydrolyses urea). Mycoplasmas/Ureaplasmas are the smallest free-living bacteria, lack a cell wall (hence Gram stain negative and beta-lactam resistant), and require cholesterol from media for growth. Mycoplasma genitalium causes non-gonococcal urethritis and cervicitis but grows extremely slowly (>1 month) and is typically diagnosed by PCR. Chlamydia is an obligate intracellular organism requiring cell culture or NAAT. Neisseria grows on Thayer-Martin (not PPLO agar) in 24–48 hrs.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.