Antimicrobial susceptibility testing (AST)

Definition

Antimicrobial susceptibility testing (AST) determines the effectiveness of specific antimicrobial agents against bacteria or fungi. It helps guide appropriate treatment by identifying resistant and susceptible strains.

5 Must Know Facts For Your Next Test

1. AST is essential for selecting the correct antimicrobial therapy for infections.
2. Common methods include disk diffusion (Kirby-Bauer), broth dilution, and E-test.
3. Results are typically reported as Minimum Inhibitory Concentrations (MICs).
4. AST can help track the emergence of antibiotic-resistant pathogens.
5. Standardized guidelines from organizations like CLSI and EUCAST are used to interpret AST results.

Review Questions

• What are common methods used in antimicrobial susceptibility testing?
• How does AST contribute to combating antibiotic resistance?
• What do MIC values indicate in the context of AST?

Related terms

Minimum Inhibitory Concentration (MIC):

The lowest concentration of an antimicrobial agent that prevents visible growth of a microorganism.

Disk Diffusion Method: A technique where antibiotic-impregnated disks are placed on an agar plate inoculated with bacteria to measure inhibition zones.

Broth Dilution Method: A method that determines the MIC by diluting antibiotics in broth containing a standardized number of bacteria.