In disk diffusion interpretation, into which categories are zone sizes typically classified?

In disk diffusion interpretation, into which categories are zone sizes typically classified?

• A. Positive, Negative
• B. Susceptible, Intermediate, or Resistant
• C. Effective, Ineffective
• D. Active, Inactive

Answer: (B)

Disk diffusion results are interpreted by comparing the measured zone of inhibition to standardized breakpoints, turning a physical size into a practical clinical decision. The goal is to categorize the isolate into three groups that guide therapy: susceptible, meaning the antibiotic will likely work at standard doses; intermediate, meaning it may work under certain conditions or with higher doses or favorable site factors; and resistant, meaning the antibiotic is unlikely to be effective. This three-category framework is the established approach because it directly translates lab measurements into actionable treatment options. Choices like positive/negative, effective/ineffective, or active/inactive don’t align with the standard interpretive system used for disk diffusion.

Disk diffusion results are interpreted by comparing the measured zone of inhibition to standardized breakpoints, turning a physical size into a practical clinical decision. The goal is to categorize the isolate into three groups that guide therapy: susceptible, meaning the antibiotic will likely work at standard doses; intermediate, meaning it may work under certain conditions or with higher doses or favorable site factors; and resistant, meaning the antibiotic is unlikely to be effective. This three-category framework is the established approach because it directly translates lab measurements into actionable treatment options. Choices like positive/negative, effective/ineffective, or active/inactive don’t align with the standard interpretive system used for disk diffusion.