Prosthetic joint infection as an unusual presentation of Francisella tularensis causing exposure of laboratory personnel.

BACKGROUND: Infections with Francisella tularensis subsp. tularensis (type A) is highly virulent with mortality up to 30 % in untreated cases. Francisella tularensis subsp. holarctica (type B) is both less infectious and virulent. Physicians/clinicians are often unfamiliar with epidemiological and clinical characteristics of tularaemia. F. tularensis type A has caused laboratory-acquired infections therefore diagnostic laboratories should be notified of samples from patients with suspected tularaemia, but breaches of laboratory safety measures still occur as tularaemia is not always recognised as a potential differential diagnosis.

CASE PRESENTATION: A 70-year-old male with a history of type-2 diabetes and a primary total knee arthroplasty (TKA) 18 years earlier, was hospitalized with pneumonia in July 2024. The respiratory symptoms resolved on piperacillin-tazobactam, however the patient reported chronic pain in his TKA on admission, and these symptoms persisted. In August 2024 the TKA was replaced, and Francisella tularensis was cultured from the periprosthetic tissue samples. Since tularaemia was not suspected, and the microbiological laboratory not alerted, two laboratory scientists were potentially exposed to Francisella bacteria. One of the two medical laboratory scientists received post-exposure antibiotic prophylaxis, neither developed infection.

CONCLUSION: We present the first reported case of periprosthetic joint associated F. tularensis infection in Denmark. Unexpected culture of F. tularensis may be accompanied by pathogen exposure of laboratory personnel that generate concern and anxiety. Most laboratory associated infections are caused by F. tularensis type A, thus guidelines taking subspecies virulence and infectivity into consideration may be relevant, especially in a European context.