Septic arthiritis due to Prevotella bivia in a patient with rheumatoid arthritis.

Prevotella bivia is a gram-negative anaerobic bacteria traditionally classified in the genus Bacteroides, and usually reported in obstetric and gynecologic infections. To date, there has been only one description of infectious arthritis secondary to this germ. We report the first case of septic arthritis due to Prevotella bivia in a patient with severe, long-lasting rheumatoid arthritis (RA) treated with low doses of corticosteroids. RA is a well-known predisposing factor to septic arthritis, whose causes are multifactorial (general immunosuppression induced by the disease and its therapy, presence of prosthetic joints, etc.). However, infectious arthritis due to anaerobic bacteria is rarely observed. In general, clinical presentation varies widely: insidious onset, apyrexia, and lack of inflammatory signs or systemic disturbance are frequent features. Joint infection is generally secondary to hematogenous spread, the Bacteroides fragilis group being the most commonly isolated pathogens. Early diagnosis and prompt treatment, with drainage and debridement of the affected joint and specific antimicrobial treatment with Metronidazole are essential for a successful outcome.