Genetic basis for vancomycin-enhanced cephalosporin susceptibility in vancomycin-resistant enterococci revealed using counterselection with dominant-negative thymidylate synthase
| Autor: | Jaime L. Little, Dušanka Djorić, Christopher J. Kristich |
|---|---|
| Rok vydání: | 2013 |
| Předmět: |
Penicillin binding proteins
medicine.drug_class Cephalosporin Antibiotics Microbial Sensitivity Tests Glycopeptide antibiotic Enterococcus faecalis Microbiology chemistry.chemical_compound Drug Delivery Systems Mechanisms of Resistance medicine Penicillin-Binding Proteins Pharmacology (medical) Cephalosporin Resistance Pharmacology biology Reverse Transcriptase Polymerase Chain Reaction Vancomycin Resistance Thymidylate Synthase biochemical phenomena metabolism and nutrition biology.organism_classification Anti-Bacterial Agents Cephalosporins Infectious Diseases chemistry Vancomycin Peptidoglycan Directed Molecular Evolution medicine.drug |
| Zdroj: | Antimicrobial agents and chemotherapy. 58(3) |
| ISSN: | 1098-6596 |
| Popis: | Antibiotic-resistant enterococci are major causes of hospital-acquired infections. All enterococci are intrinsically resistant to most cephalosporins, antibiotics in the beta-lactam family that impair peptidoglycan synthesis by inactivating the transpeptidases responsible for cross-linking. In addition, clinical isolates of enterococci often possess acquired resistance to vancomycin, a glycopeptide antibiotic that impairs peptidoglycan biosynthesis by a mechanism distinct from that of the beta-lactams, namely, by binding to the d -Ala- d -Ala termini found in peptidoglycan precursors to prevent their utilization by biosynthetic transglycosylases. Antimicrobial synergism between vancomycin and beta-lactams against vancomycin-resistant enterococci was originally described decades ago, but the genetic basis for synergy has remained unknown. Because a complete understanding of the mechanism underlying synergy between vancomycin and beta-lactams might suggest new targets or strategies for therapeutic intervention against antibiotic-resistant enterococci, we explored the genetic basis for synergy between vancomycin and cephalosporins in Enterococcus faecalis . To do so, we developed a counterselection strategy based on a dominant-negative mutant of thymidylate synthase and implemented this approach to create a panel of mutants in vancomycin-resistant E. faecalis . Our results confirm that vancomycin promotes synergy by inducing expression of the van resistance genes, as a mutant in which the van genes are expressed in the absence of vancomycin exhibits susceptibility to cephalosporins. Further, we show that peptidoglycan precursors substituted with d -Ala- d -Lac are not required for vancomycin-enhanced cephalosporin sensitivity. Instead, production of the d , d -carboxypeptidase VanY B is both necessary and sufficient to dramatically sensitize E. faecalis to cephalosporins. |
| Databáze: | OpenAIRE |
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