Infectious (Septic) Arthritis

infectious (septic) arthritis

Nongonococcal

Nongonococcal causes typically arise in the immune-compromised (thus in small children and the elderly), present as a monoarthritis (the knee, hip and other large weight-bearing joints have the highest propensity for septic arthritis) without extra-articular disease (meaning without tenosynovitis or dermatitis).
Joint cultures are almost always positive, blood cultures are positive about half of the time, and the outcome is mixed and can require antibiotics in conjunction with joint decompression and evacuation.
It most commonly manifests as a warm, painful joint that is infected by hematogenous spread. Note that the presentation is typically delayed if a joint prosthesis is present or, less commonly, arthrocentesis.
Staphylococcus aureus and streptococcus pyogenes are the most common cause of nongonococcal septic arthritis and osteomyelitis in adults.

S. aureus is an especially common cause because it contains microbial surface components recognizing adhesive matrix molecules (MSCRAMMS) in the cell wall peptidoglycan.

Gonococcal

Gonococcal arthritis (caused by Neisseria gonorrhoeae), instead, typically presents in young individuals as a migratory (polyarthritis) with associated tenosynovitis and dermatitis.
Joint cultures are positive in a minority of cases, blood cultures are rarely positive, and antibiotics are highly effective (previously penicillin and quinolones but now ceftriaxone followed by either doxycycline or cefixime).

Image Sources

“Neisseria Gonorrhoeae on Chocolate Columbia Horse Blood Ag… | Flickr.” Accessed June 18, 2021. https://www.flickr.com/photos/nathanreading/6652875905.

Reading, Nathan. Staphylococcus Aureus on Columbia Horse Blood Agar (2). February 9, 2011. Photo. https://www.flickr.com/photos/nathanreading/5866841707/.