The etiologic agent of the majority of adult joint infections is which organism?

The etiologic agent of the majority of adult joint infections is which organism?

• A. Abiotrophia sp.
• B. Leuconostoc sp.
• C. Staphylococcus aureus
• D. Streptococcus pneumoniae

Answer: (C)

Staphylococcus aureus is the most common cause of septic arthritis in adults. It frequently originates from skin colonization and can spread hematogenously to a joint, leading to acute, purulent arthritis that can progress rapidly if not treated. Among the organisms listed, Abiotrophia and Leuconostoc are rare causes of adult joint infections, while Streptococcus pneumoniae does cause arthritis but occurs less often overall than S. aureus in adults. Therefore, Staphylococcus aureus best explains the majority of adult joint infections.

Staphylococcus aureus is the most common cause of septic arthritis in adults. It frequently originates from skin colonization and can spread hematogenously to a joint, leading to acute, purulent arthritis that can progress rapidly if not treated. Among the organisms listed, Abiotrophia and Leuconostoc are rare causes of adult joint infections, while Streptococcus pneumoniae does cause arthritis but occurs less often overall than S. aureus in adults. Therefore, Staphylococcus aureus best explains the majority of adult joint infections.