Which organism is commonly associated with recurrent UTIs and staghorn calculi due to urease production?

• A. E. coli
• B. Proteus
• C. Klebsiella
• D. Pseudomonas

Answer: (B)

The main idea is that certain bacteria produce urease, an enzyme that splits urea into ammonia and carbon dioxide. This reaction raises the urine pH, making the environment alkaline. Alkaline urine promotes the formation of magnesium ammonium phosphate stones, known as struvite, which can grow rapidly into large, branching stones called staghorn calculi that fill the renal pelvis and calyces. Proteus species are classic urease producers and are strongly linked to recurrent UTIs with these stone types, especially Proteus mirabilis. While other organisms like E. coli, Pseudomonas, and Klebsiella can cause UTIs, they are not as characteristically associated with urease-driven struvite stone formation and staghorn calculi as Proteus.