Vancomycin, an antibiotic isolated from a Borneo soil sample in the 1950s, was initially known as compound 05865. It was named “vancomycin” to “vanquish” Staphylococcal infections. Despite early challenges with purity, which led to its nickname “Mississippi mud,” it quickly gained approval due to its effectiveness against resistant infections. Its use later saw a resurgence in the 1980s, particularly with the rise of Clostridioides difficile infections and increasing antimicrobial resistance.
Understanding “Spectrum of Activity”
The “spectrum of activity” of an antibiotic describes the range of bacteria the drug can effectively target. Antibiotics are categorized as either narrow-spectrum or broad-spectrum based on this range. A narrow-spectrum antibiotic is effective against a limited group of bacteria, while a broad-spectrum antibiotic targets a wider variety. Understanding an antibiotic’s spectrum is fundamental for healthcare providers to select the most appropriate medication for a patient’s infection, ensuring effective treatment while minimizing the development of resistance. This knowledge helps to avoid using broad-spectrum antibiotics when a narrow-spectrum option would suffice, thus preserving the effectiveness of these broader drugs.
Bacteria Targeted by Vancomycin
Vancomycin primarily targets Gram-positive bacteria. These bacteria possess a thick peptidoglycan cell wall that retains a purple stain in a laboratory procedure known as Gram staining. This thick, exposed cell wall makes Gram-positive bacteria susceptible to vancomycin. The antibiotic works by interfering with the construction of this cell wall, specifically by binding to particular building blocks (D-alanyl-D-alanine) of peptidoglycan, which prevents their proper incorporation and cross-linking. This action leads to a weakened cell wall, causing the bacterial cell to swell and eventually burst.
Vancomycin is active against several common Gram-positive bacteria, including:
Staphylococcus aureus (both methicillin-susceptible and methicillin-resistant strains, such as MRSA)
Staphylococcus epidermidis
Various Streptococcus species (including penicillin-resistant strains)
Enterococcus species
Clostridioides difficile, a bacterium known for causing severe intestinal infections
Infections Treated by Vancomycin
Given its specific activity against Gram-positive bacteria, vancomycin is commonly prescribed for a range of serious infections. Intravenous vancomycin is used for complicated skin and soft tissue infections, bloodstream infections (septicemia), and bone and joint infections like osteomyelitis, especially when caused by susceptible organisms, including MRSA. It is also a treatment option for endocarditis and bacterial meningitis.
For Clostridioides difficile infection (CDI), vancomycin is administered orally because it is poorly absorbed into the bloodstream when taken by mouth, allowing it to act directly in the intestines where the infection resides. This oral administration is reserved for severe cases of CDI or when other treatments are ineffective. Oral vancomycin is not suitable for systemic infections in other parts of the body.
The Challenge of Vancomycin Resistance
Antibiotic resistance occurs when bacteria evolve to withstand antibiotics, limiting treatment options for bacterial infections. Vancomycin resistance has emerged in various bacterial strains, notably in Methicillin-resistant Staphylococcus aureus (MRSA), leading to Vancomycin-intermediate Staphylococcus aureus (VISA) and Vancomycin-resistant Staphylococcus aureus (VRSA). Vancomycin-resistant Enterococci (VRE), first identified in 1986, also represent a major concern.
Bacteria develop vancomycin resistance by modifying the D-alanyl-D-alanine target site in their cell wall. This alteration reduces vancomycin’s ability to bind, making the antibiotic ineffective. Vancomycin resistance can render infections difficult to treat, sometimes positioning vancomycin as a “drug of last resort” for certain resistant strains. Therefore, careful use of vancomycin is encouraged to preserve its effectiveness against susceptible infections.