Coagulase test: Difference between revisions

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

Revision as of 18:19, 23 August 2020