Vancomycin-resistant Enterococcus (VRE) with vanA genotype shows which pattern of resistance?
- A Low-level resistance to vancomycin only, susceptible to teicoplanin
- B Intrinsic low-level vancomycin resistance with susceptibility to teicoplanin
- C High-level resistance to vancomycin and teicoplanin ✓
- D Variable resistance depending on inoculum size
Correct answer: C. High-level resistance to vancomycin and teicoplanin
Explanation
vanA encodes D-Ala-D-Lac ligase, replacing D-Ala-D-Ala in the peptidoglycan precursor, resulting in high-level resistance to both vancomycin (MIC ≥64 mg/L) and teicoplanin (MIC ≥16 mg/L). vanB confers resistance to vancomycin but retains susceptibility to teicoplanin. vanC is intrinsic to E. gallinarum/E. casseliflavus with low-level, constitutive resistance. This distinction is clinically critical when choosing alternative agents such as linezolid or daptomycin.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.