In sexually active adolescents, which organism is a common cause of septic arthritis?

• A. Haemophilus influenzae
• B. Neisseria gonorrhoeae
• C. Pseudomonas aeruginosa
• D. Staphylococcus aureus

Answer: (B)

In sexually active adolescents, septic arthritis is most often caused by a disseminated infection with Neisseria gonorrhoeae. This organism can spread from a mucosal gonorrheal infection into the bloodstream and seed joints, leading to septic arthritis. The presentation in this group is classically linked to gonococcal infection, which may present with migratory joint pain and sometimes accompanying tenosynovitis or dermatitis, rather than the pure, purulent arthritis more commonly caused by Staphylococcus aureus in other settings.

Though Staphylococcus aureus is the overall most common cause of septic arthritis across many age groups, the epidemiology shifts in this specific population toward Neisseria gonorrhoeae due to the higher likelihood of hematogenous spread from a urogenital infection. Other organisms like Haemophilus influenzae and Pseudomonas aeruginosa are less typical in this scenario: Haemophilus influenzae was more common in young children before vaccination, and Pseudomonas is usually linked to different risk factors such as puncture wounds or healthcare exposures.

So, the best answer reflects the age and sexual activity context: Neisseria gonorrhoeae.