Coagulase test: Difference between revisions

Revision as of 18:19, 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, 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

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-* Used to differentiate [[Staphylococcus aureus]] from less pathogenic [[coagulase-negative staphylococci]]
+*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)
+*Tests for the ability of the organism to convert fibrinogen into fibrin (that is, to form a clot)
-* '''Slide coagulase'''
+*'''Slide coagulase'''
-** Checks for agglutination after a drop of plasma is combined with a suspension of the bacteria on a slide
+**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
+**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
+**A few species of [[coagulase-negative staphylococci]] may be positive, including [[Staphylococcus lugdenensis]] and [[Staphylococcus intermedius]]
-** [[S. aureus]] is negative in 15% of tests, especially MRSA, so negative results need to be confirmed with tube coagulase
+**[[Staphylococcus aureus]] is negative in 15% of tests, especially MRSA, so negative results need to be confirmed with tube coagulase
-* '''Tube coagulase'''
+*'''Tube coagulase'''
-** Mix a heavy inoculum of bacteria into a tube filled with rabbit plasma
+**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
+**Positive if clot is formed within 4 hours when incubated at 37ºC
-** A few species of [[Coagulase-negative staphylococci]] may be positive
+**A few species of [[Coagulase-negative staphylococci]] may be positive
 [[Category:Diagnostics]]