# Acute Haematogenous Revision Total Knee Arthroplasty Infection by Streptococcus canis Treated by Debridement, Antibiotics, and Implant Retention: A Case Report

## TL;DR

A rare case of knee joint infection caused by Streptococcus canis was successfully treated with surgery and antibiotics.

## Contribution

This case report highlights Streptococcus canis as a rare cause of joint infection and DAIR as an effective treatment.

## Key findings

- Streptococcus canis was identified as the causative agent of an acute haematogenous infection in a revision knee arthroplasty.
- The patient was treated with debridement, antibiotics, and implant retention (DAIR) and remained asymptomatic after one year.
- The case suggests that DAIR is a viable treatment option for Streptococcus canis infections in joint prostheses.

## Abstract

Prosthetic joint infections (PJIs) are one of the most feared complications by orthopaedic surgeons. Haematogenous PJI represents an important part of PJI cases. Streptococcus canis is an extremely rare cause of haematogenous PJI and its medical and surgical treatment and prognosis are not well established.

We present a 79-year-old female patient who had a revision total knee arthroplasty (rTKA) surgery three years before. She was admitted to the hospital referring to three days of knee pain, restricted range of motion, and fever. Blood tests demonstrated leukocyte and C-reactive protein elevation. Joint fluid aspiration showed elevated white blood cell count with a high neutrophil differential and its conventional culture was positive for Streptococcus canis. She did not have pets but she took care of her daughter's dog. An acute haematogenous infection of the rTKA was diagnosed and treated with debridement, antibiotics (eight weeks of IV ceftriaxone), and implant retention (DAIR). After one year, the patient remains clinically asymptomatic without changes on X-rays and with normal serum levels of inflammatory blood markers.

Streptococcus canis has to be kept in mind as a possible cause of haematogenous TKA infection in patients who have contact with domestic pets and patients should be asked for this contact. We recommend DAIR as a viable treatment option for this type of infection, which may show excellent results.