Which organism is urease positive and commonly associated with peptic ulcers?

• A. Helicobacter pylori
• B. Escherichia coli
• C. Proteus mirabilis
• D. Klebsiella pneumoniae

Answer: (A)

Urease production enabling survival in the acidic stomach is what makes Helicobacter pylori the organism associated with peptic ulcers. H. pylori uses urease to hydrolyze urea into ammonia and carbon dioxide, and the resulting ammonia raises the local pH around the bacteria. This neutralized microenvironment lets the bacterium colonize the gastric mucosa, where it can cause chronic gastritis and ulceration. The enzyme is also why a rapid urease test on gastric tissue can quickly indicate H. pylori infection. Other urease-positive bacteria exist, but they don’t typically inhabit the stomach or cause peptic ulcers—Proteus mirabilis and Klebsiella pneumoniae are more commonly linked to urinary and other infections, while Escherichia coli is not a classic urease producer tied to gastric ulcers.