Capnocytophaga canimorsus - An underestimated cause of periprosthetic joint infection?

Background: Periprosthetic joint infection (PJI) is a major clinical problem in orthopedic surgery. Capnocytophaga canimorsus (C. canimorsus) is an unusual and hardly detectable bacterium. A review of the literature indicates that C. canimorsus affects mainly immunocompromised patients. It has not been reported to cause periprosthetic joint infections in immunocompetent patients so far. This case report aims to raise awareness of C. canimorsus in orthopedic surgery with special regard to joint arthroplasty.

Methods: We report a case of a 54-year-old immunocompetent patient with a late infection after total knee arthroplasty caused by C. canimorsus. The patient underwent two-stage revision with prosthesis explantation, implantation of an antibiotic-impregnated static spacer, intravenous antimicrobial therapy for four weeks with cefuroxime followed by oral antimicrobial therapy with ciprofloxacin for further two weeks and secondary revision total knee arthroplasty.

Results: In the present case, we could demonstrate that adequate treatment of C. canimorsus was capable to successfully treat periprosthetic joint infection caused by C. canimorsus in an immunocompetent patient.

Conclusion: We feel that C. canimorsus has to be taken into account as a potential pathogen causing periprosthetic joint infection - regardless of the immunological status of the patient and especially when the detection of a pathogen does not succeed.