Disk diffusion results interpretation relies on what to categorize results into susceptible, intermediate, or resistant?

Disk diffusion results interpretation relies on what to categorize results into susceptible, intermediate, or resistant?

• A. Breakpoints established by CLSI or EUCAST.
• B. The color of the agar.
• C. The patient's age.
• D. The lab's preferred chart.

Answer: (A)

Disk diffusion interpretation hinges on standardized breakpoints that translate the measured zone of inhibition into clinical categories: susceptible, intermediate, or resistant. These breakpoints are published by organizations such as CLSI or EUCAST and are based on factors like achievable drug concentrations at the infection site, pharmacodynamics, and clinical outcomes. The color of the agar, the patient’s age, or a lab’s internal chart do not determine susceptibility; only the established breakpoints tell you where a given zone diameter falls. If there’s no breakpoint for a particular drug–organism pair, the result can’t be interpreted reliably and may require reference to alternative methods or guidance.

Disk diffusion interpretation hinges on standardized breakpoints that translate the measured zone of inhibition into clinical categories: susceptible, intermediate, or resistant. These breakpoints are published by organizations such as CLSI or EUCAST and are based on factors like achievable drug concentrations at the infection site, pharmacodynamics, and clinical outcomes. The color of the agar, the patient’s age, or a lab’s internal chart do not determine susceptibility; only the established breakpoints tell you where a given zone diameter falls. If there’s no breakpoint for a particular drug–organism pair, the result can’t be interpreted reliably and may require reference to alternative methods or guidance.