E-testing is available for which of the following?

• A. Newer drugs and expanded MIC ranges
• B. Older antibiotics only
• C. Only Gram-positive bacteria
• D. Not used in clinical labs

Answer: (A)

E-testing determines the minimum inhibitory concentration (MIC) using a gradient strip that releases antibiotic across a continuous range of concentrations on an inoculated agar. You read the MIC where bacterial growth meets the strip’s gradient. Because the strip spans a broad, continuous range of concentrations, it can accommodate higher or atypical MIC values associated with newer drugs, giving precise results where fixed-dilution methods might miss or under- or overestimate activity. That flexibility—meeting the needs of newer antibiotics with expanded or different MIC ranges—makes E-testing available for newer drugs and expanded MIC ranges. It isn’t limited to older antibiotics, nor restricted to a single bacterial group, and it remains a common tool in clinical labs for obtaining MICs.