For surveillance screening of stool or rectal swab specimens for vancomycin-resistant enterococci, which medium and antibiotic concentration constitute the standard vancomycin screen?

• A Mueller-Hinton agar containing 30 mg/L vancomycin
• B Brain-heart infusion agar containing 6 mg/L vancomycin ✓
• C MacConkey agar containing 10 mg/L teicoplanin
• D Tryptic soy agar containing 2 mg/L vancomycin

Explanation

The CLSI-recommended vancomycin agar screen for enterococci uses brain-heart infusion agar supplemented with 6 mg/L vancomycin. B heavy inoculum is spotted onto the surface and any growth after 24 hours of incubation suggests vancomycin resistance, requiring confirmation by MIC determination and species identification. Mueller-Hinton agar is the base for disk diffusion and dilution MIC methods, not this screen, and the other media or concentrations do not correspond to any accepted screening protocol.

Reference: Koneman's Color Atlas and Textbook of Diagnostic Microbiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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