ureasepositive

Urease-positive refers to organisms that produce urease, an enzyme capable of hydrolyzing urea into ammonia and carbon dioxide. The term is commonly used in microbiology to describe bacteria and some fungi with detectable urease activity, in contrast to urease-negative organisms that do not produce this enzyme or do so at undetectable levels.

Urease is a nickel-containing metalloenzyme that catalyzes the reaction urea + water → CO2 + 2 NH3. The released ammonia raises the local pH, which can help bacteria survive in acidic environments and influence nitrogen cycles in soils and aquatic systems. In pathogenic contexts, urease activity can contribute to virulence by promoting colonization or tissue damage through pH changes.

In humans, urease-positive bacteria such as Helicobacter pylori use urease to neutralize stomach acid, enabling colonization of the gastric mucosa. In urinary tract infections, Proteus species are commonly urease-positive and can contribute to stone formation due to alkalinization of urine. Klebsiella species are also known to be urease-positive, with implications for pathogenesis and diagnostic testing.

Urease activity has diagnostic and clinical relevance. Rapid urease tests performed on gastric biopsy samples detect urease activity and support Helicobacter pylori infection diagnosis. The urea breath test measures labeled CO2 after administration of labeled urea and is a noninvasive tool for the same purpose. Urease activity is also exploited in environmental and industrial contexts, such as monitoring nitrogen cycling or in biotechnological applications under appropriate conditions.

Limitations include variability in expression depending on pH, available nickel, and nitrogen sources, as well as strain-to-strain differences that can affect the detectability of urease activity.