Which organism is most commonly associated with osteomyelitis?

• A. Escherichia coli
• B. Klebsiella sp.
• C. Staphylococcus aureus
• D. Pseudomonas aeruginosa

Answer: (C)

Staphylococcus aureus is most commonly associated with osteomyelitis because it is a frequent skin and nasal colonizer with a set of virulence factors that help it reach bone, invade bone tissue, and persist there. It readily causes hematogenous spread to bone, which is a common route for osteomyelitis, especially in children where the metaphyses of long bones are sites of vulnerability, and in adults with soft-tissue infections or implants. Its tools—such as protein A, enzymes that break down tissue, and the ability to form biofilms on hardware—make it particularly adept at establishing and sustaining bone infections.

The other organisms can cause osteomyelitis but are less common overall or are associated with specific scenarios. E. coli and Klebsiella are more often linked to osteomyelitis in adults with urinary or biliary sources or certain comorbidities, while Pseudomonas is typically seen with puncture wounds, burns, or device-related infections.