An unexpected pathogen causing prosthetic joint infection following screening colonoscopy

A 61-year-old woman with a right total knee arthroplasty presented with 1 week of atraumatic right knee swelling, pain, and fevers 2 weeks following a routine screening colonoscopy. Aspiration was concerning for prosthetic joint infection and she underwent definitive treatment with irrigation and debridement with polyethylene exchange followed by a 6-week course of oral metronidazole. Cultures speciated as Bacteroides fragilis with the presumed source being the colonoscopy causing transient bacteremia and subsequent seeding of the right knee. This case highlights the need for consideration of guidelines regarding prophylactic antibiotics to prevent prosthetic joint infection after endoscopic procedures.