Glycopeptides
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Mode of action:
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Inhibition of cell wall synthesis. Glycopeptides bind to precursors of cell wall synthesis which leads to interference of the penicillin-binding protein (PBP) enzymes such as transpeptidases to incorporate the precursors into the growing cell wall. With this, cell wall synthesis stops and cell death often follows.
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Example: |
Vancomycin, teicoplanin, avoparcin
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Source: |
Various species of actinomycetes such as Streptomyces orientalis (vancomycin), Nocardia actinoides (Actinoidin) |
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Spectrum of activity: |
Narrow spectrum affecting only Gram positive bacteria
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Effect on bacteria: |
Bactericidal
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Examples of applications in Veterinary Medicine: |
Vancomycin: “Last resort” drug in human medicine with very few applications in animals.
Avoparcin: used extensively for growth promotion of chickens and pigs.
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Miscellaneous:
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Ristocetin, although also bactericidal like vancomyin, was discontinued for use as an antibiotic because it causes aggregation of blood platelets. However, this unfavorable attribute was put to good use in helping to diagnose von Willebrand’s disease.
Some glycopeptides like avoparcin, A-4696 or actaplanin and A35512 are being marketed and used as feed additive in some countries. When it became apparent that avoparcin selected for VRE (vancomycin resistant enterococci) in animals, Denmark and subsequently all of Europe withdrew it from animal feeds to reduce risk for humans. The ban in Denmark was reportedly followed by an immediate decrease in VRE isolates in poultry, but not in pigs, until tylosin was also banned from use in feed (Aarestrup et al., 2001). |
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