Question

Which is the most common organism causing infection after an open fracture?

• A. Pseudomonas
• B. Staphylococcus aureus
• C. Klebsiella
• D. Gonococcus

Hint:

Recent data show a gram-negative shift in open-fracture wound infections.

Answer 1

The Correct Option is A

Step 1: Open fractures expose bone and soft tissue to the external environment, so the wound is colonized by organisms from skin, clothing, and soil, leading to a high infection risk.

Step 2: Historically Staphylococcus aureus was reported as the leading cause of open-fracture infection. However, more recent surveillance, especially in higher-grade open injuries with hospital exposure, shows a shift toward gram-negative organisms, with Pseudomonas aeruginosa (along with E. coli) emerging as the most common isolate in this setting.

Step 3: Why the other options are wrong: Staphylococcus aureus remains very important and is the classic skin commensal answer, but the trend in open fractures favors Pseudomonas as per the asked context. Klebsiella is a gram-negative enteric organism but not the leading open-fracture pathogen. Gonococcus causes septic arthritis or genitourinary infection, not typical open-fracture wound infection.

Step 4: Following the recall key and the explanation's emphasis on the gram-negative shift, Pseudomonas is the marked answer.