Rat bite fever in a total knee arthroplasty: an unusual case of periprosthetic joint infection.

Background: Periprosthetic joint infection (PJI) is a serious complication of orthopedic arthroplasty surgery. Rat bite fever is a rare infection with Streptobacillus moniliformis (S. moniliformis). Rat bite fever can lead to serious complications such as pyogenic infection of joints, bacteremia, endocarditis and even death. We hereby present the first case of a patient with a total knee arthroplasty, infected with S. moniliformis, successfully treated by surgical debridement, antibiotics and implant retention (DAIR).

Case Presentation: The patient was a 64-year-old female. S. moniliformis was isolated from blood cultures and an aspirate of the left knee by 16S rRNA gene polymerase chain reaction technique. It was assumed that the S. moniliformis had a systemic origin and secondarily infected the knee due to fever nine days before the onset of symptoms of the knee. The patient was successfully managed with DAIR and intravenous administration of ceftriaxone for six weeks and oral doxycycline for another six weeks.

Conclusions: S. moniliformis is a rare pathogen and is difficult to culture. The 16S rRNA sequencing is helpful in the determination of a causative microorganism in the case of a culture-negative PJI. A DAIR procedure in combination with 12 weeks of antibiotics could successfully treat S. moniliformis prosthetic joint infection.