Vancomycin is a powerful antibiotic used to treat serious bacterial infections. It is often reserved for situations where other treatments are ineffective, primarily due to its specific action against certain bacteria.
Understanding Vancomycin
Vancomycin is a glycopeptide antibiotic, discovered in the 1950s from a soil bacterium. This historical context highlights its long-standing presence in combating bacterial pathogens. It initially gained a reputation as a “last-resort” antibiotic due to early formulations having notable side effects, and penicillin being effective for most infections. However, as antibiotic resistance emerged and purification methods improved, vancomycin’s use became more widespread, establishing its role as a potent treatment.
How Vancomycin Targets Bacteria
Vancomycin interferes with the construction of bacterial cell walls. Bacterial cells require a robust cell wall, primarily composed of peptidoglycan, for their integrity and survival. Vancomycin specifically binds to the D-alanyl-D-alanine (D-Ala-D-Ala) portion of peptidoglycan precursors. This binding prevents the necessary cross-linking of these building blocks, which weakens the bacterial cell wall and makes it vulnerable to osmotic pressure, leading to its death. This mechanism makes vancomycin effective against bacteria that rely on this specific cell wall structure.
Key Infections Vancomycin Treats
Vancomycin treats severe infections caused by Gram-positive bacteria, which have a thick peptidoglycan layer in their cell wall. A primary use is for Methicillin-resistant Staphylococcus aureus (MRSA) infections. MRSA has developed resistance to many common antibiotics. Vancomycin is a first-line treatment for various MRSA infections, including those affecting the bloodstream, skin, bones, joints, and pneumonia.
Vancomycin also treats Clostridioides difficile (C. diff) infection, which causes severe diarrhea and colitis, especially in patients who have recently received other antibiotics. For C. diff, vancomycin is administered orally. This ensures high concentrations of the antibiotic reach the localized infection in the gastrointestinal tract, as systemic absorption is not needed.
Optimizing and Monitoring Vancomycin’s Strength
Vancomycin’s effectiveness is influenced by bacterial resistance and patient management. Some bacteria have developed resistance, including Vancomycin-resistant Enterococci (VRE) and Vancomycin-intermediate Staphylococcus aureus (VISA). VRE alter the binding site, while VISA thicken cell walls and produce excess targets, trapping vancomycin.
Therapeutic drug monitoring (TDM) is used to measure vancomycin levels in a patient’s blood. This ensures concentrations are within an effective and safe range. Maintaining appropriate trough concentrations, the lowest drug levels between doses, helps prevent resistance and achieve the desired effect. Current recommendations suggest a target trough concentration between 10 to 15 mg/L for most adult patients to balance efficacy and reduce kidney injury risk.
The route of administration also impacts effectiveness. For systemic infections like bloodstream infections or pneumonia, vancomycin is given intravenously. For C. diff infections confined to the bowel, oral vancomycin is used because it is poorly absorbed into the bloodstream. This localized delivery ensures the antibiotic reaches the bacteria in the colon. Vancomycin is reserved for serious infections, especially those caused by resistant Gram-positive bacteria, to preserve its effectiveness and combat antibiotic resistance.