Which of the following enzymes is used to detect the presence of H pylori infections?

• A. DNase
• B. Hyaluronidase
• C. Peptidase
• D. Urease

Answer: (D)

Urease activity is exploited to detect Helicobacter pylori because this bacterium uniquely and robustly produces urease in the acidic stomach environment. The diagnostic tests rely on that activity. In the urea breath test, a patient drinks urea labeled with a carbon isotope; if H. pylori is present, its urease splits the urea to CO2 and ammonia, and the labeled CO2 shows up in the breath. In the rapid urease test on gastric tissue, a biopsy sample is placed in a medium containing urea and a pH indicator; if urease is present, ammonia produced raises the pH and the indicator changes color, signaling infection. This enzymatic activity serves as a practical and specific marker of active H. pylori infection. The other enzymes listed are not used for diagnosing H. pylori because they’re not the diagnostic signal relied upon for this organism.