What is the primary purpose of the coagulase test?

What is the primary purpose of the coagulase test?

• A. It distinguishes Staphylococcus aureus from other Gram-positive cocci
• B. It detects motility
• C. It measures lactose fermentation
• D. It differentiates Gram-negative rods from cocci

Answer: (A)

The coagulase test identifies whether a bacterium produces coagulase, an enzyme that clots plasma by converting fibrinogen to fibrin. Staphylococcus aureus typically makes coagulase, whereas most other Staphylococcus species (coagulase-negative) do not, so a positive test helps distinguish S. aureus from other Gram-positive cocci. The other options describe different traits (motility, lactose fermentation, or differentiating Gram-negative rods from cocci) that are not determined by coagulase testing, so they don’t serve this identification purpose.

The coagulase test identifies whether a bacterium produces coagulase, an enzyme that clots plasma by converting fibrinogen to fibrin. Staphylococcus aureus typically makes coagulase, whereas most other Staphylococcus species (coagulase-negative) do not, so a positive test helps distinguish S. aureus from other Gram-positive cocci. The other options describe different traits (motility, lactose fermentation, or differentiating Gram-negative rods from cocci) that are not determined by coagulase testing, so they don’t serve this identification purpose.