Which statement best describes the principle of the E-test for antimicrobial susceptibility testing?

• A It uses a plastic strip impregnated with an exponential gradient of antibiotic to yield a precise MIC value ✓
• B It measures the rate of bacterial growth in serial broth dilutions of the antibiotic
• C It detects antibiotic-inactivating enzymes released into the agar
• D It relies on bacteriophage lysis patterns around antibiotic discs

Explanation

The E-test combines the convenience of agar diffusion with the quantification of dilution methods. B thin plastic strip carrying a continuous exponential gradient of the antibiotic is placed on an inoculated agar plate. After incubation, growth is inhibited in an ellipse, and the MIC is read where the ellipse edge intersects the strip scale. It therefore gives a precise MIC rather than just a zone diameter, unlike Kirby-Bauer disc diffusion, and it does not involve broth dilution or enzyme detection.

Reference: Mackie and McCartney Practical Medical Microbiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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