Susceptibility methods: Difference between revisions
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== Methods == |
== Methods == |
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=== Broth dilution === |
=== Broth dilution === |
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* Typically the gold standard |
* Typically the gold standard |
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* Can be macro- or micro-broth dilution |
* Can be macro- or micro-broth dilution |
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=== Agar dilution === |
=== Agar dilution === |
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* Same principle as broth dilution, but with agar plates |
* Same principle as broth dilution, but with agar plates |
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=== Kirby-Bauer disc diffusion === |
=== Kirby-Bauer disc diffusion === |
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* Antimicrobial disc is placed on a Mueller-Hinton plate with controlled concentration of organisms |
* Antimicrobial disc is placed on a Mueller-Hinton plate with controlled concentration of organisms |
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* Antimicrobial diffuses through the medium |
* Antimicrobial diffuses through the medium |
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=== Non-phenotypic methods === |
=== Non-phenotypic methods === |
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* Examples include PBP2a rapid detection kits, PCR for known resistance genes (e.g. mecA), etc. |
* Examples include PBP2a rapid detection kits, PCR for known resistance genes (e.g. mecA), etc. |
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== Specific Examples == |
== Specific Examples == |
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=== Double-disc testing === |
=== Double-disc testing === |
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* A variant of the Kirby-Bauer method above, but with two antimicrobial-eluting discs placed in close proximity |
* A variant of the Kirby-Bauer method above, but with two antimicrobial-eluting discs placed in close proximity |
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* Tests one antimicrobial inducing susceptibility or resistance to another antimicrobial |
* Tests one antimicrobial inducing susceptibility or resistance to another antimicrobial |
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* Example includes the clindamycin D-test, where erythromycin may induce clindamycin resistance in [[S. aureus]] |
* Example includes the clindamycin D-test, where erythromycin may induce clindamycin resistance in [[S. aureus]] |
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[[Category:Diagnostics]] |
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Latest revision as of 22:25, 1 February 2020
Methods
Broth dilution
- Typically the gold standard
- Can be macro- or micro-broth dilution
- Increasing concentration of antimicrobial in the broth until growth is inhibited (MIC)
Agar dilution
- Same principle as broth dilution, but with agar plates
Kirby-Bauer disc diffusion
- Antimicrobial disc is placed on a Mueller-Hinton plate with controlled concentration of organisms
- Antimicrobial diffuses through the medium
- Standardized cutoffs for the diameter of the zone of inhibition
Non-phenotypic methods
- Examples include PBP2a rapid detection kits, PCR for known resistance genes (e.g. mecA), etc.
Specific Examples
Double-disc testing
- A variant of the Kirby-Bauer method above, but with two antimicrobial-eluting discs placed in close proximity
- Tests one antimicrobial inducing susceptibility or resistance to another antimicrobial
- Example includes the clindamycin D-test, where erythromycin may induce clindamycin resistance in S. aureus
