Vancomycin is a powerful antibiotic used to treat serious bacterial infections. It belongs to the glycopeptide class of antibiotics, often reserved when other treatments are ineffective. This medication is a significant tool in modern medicine for combating difficult-to-treat pathogens.
What “Bactericidal” Means
Antibiotics are categorized by their effect on bacteria. A “bactericidal” antibiotic directly kills bacteria. This differs from “bacteriostatic” antibiotics, which primarily inhibit bacterial growth and reproduction. Bacteriostatic agents prevent bacteria from multiplying, allowing the body’s immune system to clear the infection.
This distinction influences treatment decisions, especially for patients with weakened immune systems or severe infections. For a drug to be classified as bactericidal, it must achieve a significant reduction in bacterial populations, often defined as a 99.9% decrease in bacterial density within 24 hours. This killing effect sets bactericidal agents apart from those that merely halt bacterial proliferation.
How Vancomycin Works
Vancomycin interferes with the construction of the bacterial cell wall, a rigid outer layer that provides structural support and protects the bacterium. It targets Gram-positive bacteria, which have a thick peptidoglycan layer in their cell wall. This layer is a mesh-like polymer of sugar chains linked by short peptides.
The antibiotic binds to the D-alanyl-D-alanine (D-Ala-D-Ala) portion of peptidoglycan precursors, the building blocks bacteria use to assemble cell walls. By binding, vancomycin prevents two steps in cell wall synthesis: transglycosylation and transpeptidation. These processes involve polymerizing precursors into long chains and cross-linking them into a stable structure. Without a properly formed cell wall, the bacterial cell weakens, cannot withstand internal osmotic pressure, and undergoes lysis, leading to its death.
When Vancomycin is Used
Vancomycin is reserved for severe infections, especially those caused by Gram-positive bacteria resistant to other common antibiotics. A primary use is against Methicillin-resistant Staphylococcus aureus (MRSA), a strain resistant to many penicillin-related antibiotics. For systemic infections like bloodstream infections, bone and joint infections, endocarditis, or meningitis caused by MRSA, vancomycin is administered intravenously.
Another application is treating infections caused by Clostridioides difficile, which can lead to severe diarrhea and colon inflammation. For C. difficile infections, vancomycin is given orally. This ensures the antibiotic acts directly in the intestines, as it is poorly absorbed into the bloodstream when taken by mouth.
Judicious use of vancomycin is important due to concerns about antibiotic resistance. Some bacteria, like vancomycin-resistant enterococci (VRE) and vancomycin-resistant Staphylococcus aureus (VRSA), have developed mechanisms to evade its effects. Healthcare providers carefully manage vancomycin prescriptions to preserve its effectiveness and combat antimicrobial resistance.