**Question:** The prophylactic antibiotic indicated to prevent infection in lymphoedema is:

A. Amoxicillin
B. Ceftriaxone
C. Vancomycin
D. Gentamicin

**Core Concept:** Lymphoedema is a chronic swelling of the limbs or other body parts due to impaired lymphatic drainage. This condition increases the risk of infection, and prophylactic antibiotics are sometimes prescribed to prevent such complications.

**Why the Correct Answer is Right:** The correct answer, Ceftriaxone, is a broad-spectrum third-generation cephalosporin with high tissue penetration and long half-life, making it an effective choice for prophylaxis in lymphoedema patients. It has a good activity against common pathogens involved in lymphoedema infections, including Gram-positive (Staphylococcus aureus, Streptococcus species) and Gram-negative bacteria (e.g., Escherichia coli, Klebsiella species).

**Why Each Wrong Option is Incorrect:**

A. Amoxicillin: A penicillin-derived antibiotic, Amoxicillin has limited tissue penetration and is less effective in treating infections in lymphoedema patients.

B. Ceftriaxone: Although effective against Gram-negative bacteria, it is not as potent against Gram-positive organisms, which are more commonly involved in lymphoedema infections.

C. Vancomycin: A glycopeptide antibiotic, Vancomycin is typically reserved for treating MRSA (Methicillin-resistant Staphylococcus aureus) infections and is not the first-choice prophylactic antibiotic.

D. Gentamicin: A spectinomycin-derived aminoglycoside antibiotic, Gentamicin has poor tissue penetration and is less effective in treating infections in lymphoedema patients.

**Clinical Pearl:** Prophylactic antibiotics in lymphoedema should be chosen based on their tissue penetration, spectrum of activity against common pathogens, and patient-specific factors such as allergies or contraindications. Ceftriaxone is a suitable option due to its broad-spectrum activity against Gram-negative bacteria, but it should be supplemented with another antibiotic with activity against Gram-positive organisms, such as linezolid, to cover a wider range of pathogens.

**Correct Answer Explanation:** Ceftriaxone is an effective antibiotic for Gram-negative bacteria, which are commonly involved in lymphoedema infections. However, it is essential to supplement Ceftriaxone with another antibiotic like Linezolid that has activity against Gram-positive organisms, as they are more commonly involved in lymphoedema infections. This combination ensures comprehensive coverage for the majority of pathogens involved in lymphoedema-related infections.