Abstract
Introduction: Septic arthritis is inflammation of the joints caused by infection with microorganisms. Generally, septic arthritis is caused by Staphylococcus aureus. Streptococcus pneumoniae is rarely found to be a cause of septic arthritis, however, inadequate treatment can increase morbidity in these cases. This case report aimed to improve the understanding of septic arthritis caused by Streptococcus pneumoniae.
Case report: A 58-year-old woman was being treated at a tertiary referral hospital in Bali for septic arthritis. She had a history of osteoarthritis and underwent prosthesis surgery on her right knee two years ago. The patient had no history of pneumonia. Her knee joint fluid culture was examined before giving empiric antibiotics. The results of synovial culture using VITEK 2 COMPACT (bioMérieux®) identified as Streptococcus pneumoniae. The clinical symptoms experienced were fever accompanied by swelling and pain in both knees with limited mobilization. This patient suffered from osteoarthritis and had a prosthesis in the right knee as a risk factor for septic arthritis. She was given antibiotic ceftriaxone as empiric antibiotic therapy just after synovial fluid collection for culture. After Streptococcus pneumoniae was identified from the culture, and the antimicrobial susceptibility testing results were still sensitive to ceftriaxone; therefore, the antibiotic continued as definitive antibiotic therapy. Clinical improvement was found on the sixth day, and she was discharged after 6 days of treatment.
Conclusions: Cases of septic arthritis in women without a history of pneumococcal pneumonia are rare but remain a problem when associated with the prosthetic joint infection. Special consideration should be given to septic arthritis patients with a history of total knee replacements. It is important to do a synovial fluid culture to identify the cause of infection and select appropriate definitive antibiotics to prevent permanent joint dysfunction.

Key words: knee joint, prosthetic joint, septic arthritis, Streptococcus pneumoniae