Catalase test is used to differentiate –
**Core Concept**
The catalase test is a biochemical test used to differentiate between catalase-positive and catalase-negative organisms. It relies on the enzyme catalase, which breaks down hydrogen peroxide into water and oxygen. This test is crucial in the identification of various bacterial species.
**Why the Correct Answer is Right**
The catalase test exploits the presence of catalase enzyme in bacteria, which catalyzes the decomposition of hydrogen peroxide (H2O2) into water (H2O) and oxygen (O2). This reaction occurs rapidly in catalase-positive bacteria, producing bubbles of oxygen gas, whereas catalase-negative bacteria do not exhibit this reaction. The test is often performed by adding a small amount of hydrogen peroxide to a bacterial culture and observing for the production of oxygen bubbles.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the catalase test, which is used to differentiate between catalase-positive and catalase-negative organisms.
**Option B:** The coagulase test is used to differentiate between Staphylococcus aureus and coagulase-negative staphylococci, and is not related to the catalase test.
**Option C:** The urease test is used to detect the presence of urease enzyme in bacteria, which breaks down urea into ammonia and carbon dioxide, and is not related to the catalase test.
**Clinical Pearl / High-Yield Fact**
The catalase test is a rapid and simple method for differentiating between catalase-positive and catalase-negative bacteria, and is often used in the identification of bacterial species in clinical microbiology laboratories.
**Correct Answer: D. Staphylococcus aureus and catalase-negative bacteria**