The first glycopeptide, vancomycin, was isolated from the organism Streptomyces in the mid-1950s. The only other glycopeptide used clinically is teicoplanin – although there are glycopeptide derivatives used in the animal industry as growth supplements.
Mechanism of action
These agents act by inhibiting cell wall synthesis, but in a different fashion to the way the beta lactams work.
Glycopeptides prevent the cell wall precursors from being transported from the cytoplasm (where they are made) to the cell wall itself (where they are incorporated into the cell wall). By interfering with cell wall synthesis, they inhibit replication, and ultimately kill the bacterium.
Route of administration
Vancomycin can only be given intravenously. If given orally, it is not absorbed very well, but it has been used to treat some infections that are limited to the gastro-intestinal tract. Teicoplanin can be given intravenously or intramuscularly. These agents, like the aminoglycosides, are thus used almost exclusively in hospitals.
Spectrum of action
Essentially, glycopeptides are active against Gram positive bacteria, and have no activity against Gram negative bacteria. As with all rules, there are some exceptions to this one as well, but they are very rare.
Because of the expense of these agents, and their potential toxicity, as well as the fact that they can only be given by injection, glycopeptides are really only used for severe infections, or for infections with organisms that are resistant to other antibiotics. They are also sometimes used if a patient is allergic to penicillin.
Organisms that are sometimes treated with glycopeptides include:
- Staphylococcus aureus and some other staphylococcal species
- Enterococcus faecalis
- Some streptococcal infections
- Infections with various Corynebacterium spp. – often involving prosthetic heart valves
Glycopeptides are potentially toxic to both the kidneys and the ears (similar to aminoglycosides). This toxicity is generally rare, but may be more likely to occur if patients are being treated with another potentially toxic agent at the same time.
Allergic reactions can also occur, and if the drug is given too rapidly, the so–called “red man syndrome” may occur. There is severe flushing of the face and neck, and possibly itching and a drop in blood pressure.