Urease-Positive Organisms
Examples: Proteus, Cryptococcus, Helicobacter pylori, Ureaplasma, Nocardia, Klebsiella, Staphylococcus epidermidis, Staphylococcus saprophyticus.
Enzyme activity:
- Urease hydrolyzes urea → releases ammonia + CO₂ → increases pH.
Clinical relevance:
- Alkalinization of urine predisposes to struvite (magnesium ammonium phosphate) stones, especially with Proteus infections.
Mnemonic: “Pee CHUNKSS”
- Proteus
- Cryptococcus
- H. pylori
- Ureaplasma
- Nocardia
- Klebsiella
- S. saprophyticus
- S. epidermidis
Learning Objective (USMLE Step 1):
Recognize urease-positive organisms and understand how urease activity increases urinary pH, predisposing to struvite stone formation in infections such as Proteus.
