Vancomycin has been ordered to treat a patient's infection. Which is true regarding vancomycin (Select all that apply)

Vancomycin is a potent glycopeptide antibiotic reserved for severe infections caused by gram-positive organisms, including MRSA. It acts by inhibiting bacterial cell wall synthesis but requires careful administration to avoid infusion-related reactions and to ensure therapeutic efficacy within the narrow therapeutic index. A. Vancomycin is a narrow-spectrum antibiotic that is primarily effective against gram-positive micro-organisms. It is ineffective against gram-negative bacteria because its large molecular size prevents it from penetrating the outer membrane of gram-negative cell walls, making it an inappropriate choice for infections caused by organisms like E. coli or Pseudomonas. B. When administered orally, vancomycin is poorly absorbed into the systemic circulation and remains within the gastrointestinal tract. This local concentration makes it the first-line treatment for Clostridioides difficile-associated pseudomembranous colitis, as the medication directly targets the pathogen residing in the lumen of the colon. C. Rapid intravenous administration of vancomycin can trigger a non-immunologic release of histamine, resulting in a condition known as red man syndrome. This is characterized by intense flushing, pruritus, and an erythematous rash affecting the face, neck, and upper torso, which can sometimes be accompanied by hypotension. D. To minimize the risk of infusion-related adverse events and thrombophlebitis, vancomycin must be administered via slow intravenous infusion. Standard clinical protocols recommend that each dose be infused over a minimum of 60 minutes, or longer if the dose exceeds 1000 mg, to maintain patient safety and hemodynamic stability. E. By definition, vancomycin-resistant enterococcus (VRE) has developed genetic mechanisms to alter its cell wall precursors, preventing vancomycin from binding to its target site. Therefore, vancomycin is clinically ineffective against VRE, and alternative antimicrobial agents such as linezolid or daptomycin must be utilized to treat these resistant infections.