In septic arthritis with suspected bacterial infection, which empiric antibiotic strategy is commonly used?

• A. Ceftriaxone alone
• B. Vancomycin alone
• C. Vancomycin plus Ceftriaxone
• D. Doxycycline plus Gentamicin

Answer: (C)

When septic arthritis is suspected, you need empiric therapy that covers both MRSA and Gram-negative bacilli because the causative organisms can vary widely and act quickly to damage the joint. Vancomycin targets gram-positive cocci, including MRSA, while ceftriaxone is a strong option for many Gram-negative organisms (and also covers Neisseria and some streptococci). Using them together provides broad initial coverage until culture results come back, increasing the likelihood of hitting the actual pathogen.

Vancomycin alone wouldn’t treat Gram-negative bacteria, and ceftriaxone alone wouldn’t reliably cover MRSA. The other combination—doxycycline with gentamicin—lacks reliable MRSA coverage and has concerns about effectiveness and toxicity in joint infections, making it a less appropriate empiric choice.