Coagulase test: Difference between revisions

Revision as of 18:20, 23 August 2020

Used to differentiate Staphylococcus aureus from less pathogenic coagulase-negative staphylococci
Tests for the ability of the organism to convert fibrinogen into fibrin (that is, to form a clot)
Slide coagulase
- Checks for agglutination after a drop of plasma is combined with a suspension of the bacteria on a slide
- Positive if clumping is apparent within 10 seconds or less, and no clumping is observed in saline or water
- A few species of coagulase-negative staphylococci may be positive due to membrane-bound clumping factor, including Staphylococcus lugdenensis and Staphylococcus intermedius
- Staphylococcus aureus is negative in 15% of tests, especially MRSA, so negative results need to be confirmed with tube coagulase
Tube coagulase
- Mix a heavy inoculum of bacteria into a tube filled with rabbit plasma
- Positive if clot is formed within 4 hours when incubated at 37ºC
- A few species of Coagulase-negative staphylococci may be positive

@@ Line 4: / Line 4: @@
 **Checks for agglutination after a drop of plasma is combined with a suspension of the bacteria on a slide
 **Positive if clumping is apparent within 10 seconds or less, and no clumping is observed in saline or water
-**A few species of [[coagulase-negative staphylococci]] may be positive, including [[Staphylococcus lugdenensis]] and [[Staphylococcus intermedius]]
+**A few species of [[coagulase-negative staphylococci]] may be positive due to membrane-bound clumping factor, including [[Staphylococcus lugdenensis]] and [[Staphylococcus intermedius]]
 **[[Staphylococcus aureus]] is negative in 15% of tests, especially MRSA, so negative results need to be confirmed with tube coagulase
 *'''Tube coagulase'''