A 26-year-old man has non-gonococcal urethritis. Culture of urine sediment on special media yields tiny colonies, and addition of urea to the medium produces a colour change with rise in pH. Which organism is identified, and what complication is it associated with?

• A Mycoplasma hominis, bacterial vaginosis
• B Ureaplasma urealyticum, struvite urinary calculi ✓
• C Mycoplasma genitalium, pelvic inflammatory disease
• D Chlamydia trachomatis, epididymitis

Explanation

Ureaplasma urealyticum is distinguished from other mycoplasmas by its urease enzyme, which splits urea to ammonia, raising the pH of the medium. It is a recognised cause of non-gonococcal urethritis and is associated with urolithiasis because alkaline urine promotes precipitation of magnesium ammonium phosphate (struvite) stones. Mycoplasma hominis does not hydrolyse urea, and C. trachomatis cannot be cultured on cell-free media at all.

Reference: Ananthanarayan and Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.