What is the antibiotic prophylaxis for open fractures?

• A. Vancomycin
• B. 1st gen cephalosporin (cefazolin) + aminoglycoside
• C. Amoxicillin
• D. 3rd gen cephalosporin

Answer: (B)

Open fractures carry a high risk of infection from skin flora and environmental organisms, so prevention needs broad but targeted coverage. A first-generation cephalosporin like cefazolin effectively covers common skin pathogens such as Staphylococcus aureus and Streptococcus species. In injuries with significant contamination or in high-risk open fractures, adding an aminoglycoside (for example gentamicin) expands coverage to Gram-negative bacilli that can be introduced from the environment, giving broader protection against the organisms most likely to cause infection.

Other options don’t provide this combination of reliable skin-flora coverage plus Gram-negative coverage: vancomycin alone targets MRSA but omits many Gram-negatives; amoxicillin alone misses key Gram-negative and resistant organisms; a third-generation cephalosporin covers more Gram-negatives but isn’t the standard regimen for open-fracture prophylaxis and may miss some Staphylococcal coverage.