USMLE Forum Archives - USMLE Step 1 - 2518
2518
babbu5508 - 12-28-10 00:50
A 60-year-old woman has been hospitalized for three weeks with widely metastatic ovarian adenocarcinoma, and she becomes septic with vancomycin-resistant enterococcus. What is the mechanism of vancomycin resistance in this organism?
Options:
A. Acetylation of antibiotic
B. Altered drug-binding protein
C. ß-lactamase production
D. Decreased ribosomal binding of antibiotic
E. Formation of novel cell wall peptide bridges
babbu5508 - 12-28-10 00:50
A 60-year-old woman has been hospitalized for three weeks with widely metastatic ovarian adenocarcinoma, and she becomes septic with vancomycin-resistant enterococcus. What is the mechanism of vancomycin resistance in this organism?
Options:
A. Acetylation of antibiotic
B. Altered drug-binding protein
C. ß-lactamase production
D. Decreased ribosomal binding of antibiotic
E. Formation of novel cell wall peptide bridges
The correct answer and explanation will be available after you answer.
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#3
Re: 2518
babbu5508 - 01-14-11 15:46 The correct answer is E. The antibiotic property of vancomycin depends upon its ability to bind D-ala-D-ala, which is vital in the synthesis of peptidoglycan peptide bridges. Vancomycin-resistant enterococci instead utilize D-lactic acid in their peptide bonds, and thus are resistant to the action of vancomycin.
#11
Re: 2518 babbu5508 - 01-31-11 22:50 B. Altered drug-binding protein accounts for drug resistance for penicillins and cephalosporins but not or vancomycin...............
#12
Re: 2518 adriannacruz - 01-03-12 16:21 My answer is: e.
Vancomycin resistant utilize lactic acid for peptide bonds hence they are resistant to vancomycin
#17
Re: 2518 berserk - 01-21-12 20:25 My answer is: e.
D-ala-D-ala to D-ala-D-lactate in NAM part of peptidoglycan layer
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