A patyient needs antibiotic treatment for aificial valve, culture-positive infective enterococcal endocarditis. His medical history includes severe anaphylactic reaction to penbicillin G during the past year. The best approach would be treatment with:
**Core Concept**
Anaphylactic reactions to penicillin G pose a significant challenge in treating enterococcal endocarditis, requiring an alternative antibiotic with a different mechanism of action. The patient's history mandates the selection of an antibiotic that is effective against Enterococcus species while avoiding cross-reactivity with penicillin G.
**Why the Correct Answer is Right**
Vancomycin is a glycopeptide antibiotic that inhibits cell wall synthesis in Gram-positive bacteria, including Enterococcus species. It is effective against penicillin-resistant strains and does not share cross-reactivity with penicillin G, making it an ideal choice for treating enterococcal endocarditis in patients with a history of anaphylaxis to penicillin. Vancomycin is typically administered intravenously and requires monitoring of renal function and serum levels to prevent toxicity.
**Why Each Wrong Option is Incorrect**
* **Option A:** Ampicillin is a penicillin antibiotic that would exacerbate the patient's anaphylactic reaction to penicillin G, making it an inappropriate choice.
* **Option B:** Ceftriaxone is a cephalosporin antibiotic that can cause cross-reactivity with penicillin G in some patients, increasing the risk of anaphylaxis.
* **Option D:** Linezolid is an oxazolidinone antibiotic that is effective against Gram-positive bacteria, including Enterococcus species. However, it is typically reserved for treatment of resistant infections and has a higher risk of adverse effects, including thrombocytopenia and peripheral neuropathy.
**Clinical Pearl / High-Yield Fact**
In patients with a history of anaphylaxis to penicillin G, vancomycin is a reliable alternative for treating enterococcal endocarditis. Always consider the patient's medical history when selecting an antibiotic to minimize the risk of adverse reactions.
**Correct Answer: C. Vancomycin**