Management of an anaerobic infection in a prosthetic knee with long-term antibiotics alone: a case report.

A 74-year-old woman had a spherocentric arthroplasty performed on her left knee. After four postoperative weeks, she developed and swelling in the joint. An anaerobic streptococcus was isolated from a joint aspirate. The patient was treated solely with knee immobilization and intravenous penicillin G for five weeks. Joint aspirates at the end of treatment and six months posttreatment were sterile. However, after ten posttreatment months, the peptostreptococcal infection recurred. Sterile joint aspirates six months after treatment are insufficient evidence of cure in prosthetic joint infections.