Brucellosis is a zoonotic infection caused by Brucella species. It can be transmitted to humans through consumption of unpasteurized and contaminated milk products or through contact with infected animals. Osteoarticular involvement is the most common focal presentation. Prosthetic joint infections (PJI) caused by Brucella spp. are uncommonly reported in the literature. It is rarely diagnosed because of uncommon symptoms. Diagnosis is usually based on serology, augmented when possible by culture of Brucella organisms from blood, synovial fluid, or bone. In this case report, we describe an infection of a total knee prosthesis caused by Brucella spp.

Brucellosis remains an endemic infection and burdensome health issue, especially in Tunisia. Strenuous efforts are required to improve the healthcare quality to prevent this type of infection. ¹

Brucella spp. are facultative intracellular gram-negative coccobacilli that are non-motile and non-spore-forming. Three species ( B. melitensis, B. abortus, and B. suis) are important human pathogens, B. canis is less important.

Osteoarticular involvement is common in brucellosis. Spondylitis, sacroiliitis, osteomyelitis, and peripheral arthritis were the most frequently reported forms of brucellosis. ²

A Tunisian article, published by H. Battikh, A. Berriche, R. Zayoud et al., reported that osteoarticular involvement was the most common complication of brucellosis, occurring in 28.5% of patients (spondylodiscitis in 20 cases and sacroiliitis in 5 cases) in a series of 109 patients. ¹

Brucella infection after total joint arthroplasty is rare and difficult to diagnose. ³

A systematic review of the literature by Kim et al. reported 18 patients who had Brucella infection following total joint arthroplasty (10 cases of hip joint arthroplasty and 8 cases of knee joint prostheses). ⁴

Our case report revealed the first case of Brucella prosthetic joint infection described in Tunisia despite the endemicity of brucellosis in our country.

The Steckelberg JO article reported that the mean rate of infections in knee and hip joint arthroplasty, between the second and tenth year after surgery, is, respectively, 2.3 and 5.9 per 1000, respectively, every year. ⁵

A single swollen and painful prosthetic joint, as observed in our patient, could be the only clinical symptom. The non-specific signs and rarity of this type of infection make the diagnosis very difficult to establish. ⁶

The median duration from prosthesis implantation to the onset of symptoms was 3.9 years in a systematic review of literature by Kim et al. ⁴ We report a similar duration in our case. The onset of symptomatology was four years after prosthesis implantation.

Standard radiography did not always show evidence of prosthetic loosening; CT could help, in certain cases, diagnose prosthetic migration and peri-prosthetic tissue damage (abscess, …). ⁷ In our case, a CT scan was performed, which showed prosthetic loosening, joint effusion, and osteolysis in contact with prosthesis components.

The diagnosis of Brucella infection following total joint arthroplasty can be established based on symptoms (pain, tenderness, and swelling of the prosthetic joint) in the presence of an antibody titer greater than 1/160 in a tube agglutination test (however, the antibody titer in our case was only 1/80). Definitive diagnosis of this infection is based on isolating Brucella spp. from intraoperative sample culture or blood culture. ^{2 , 3}

Routine treatment usually includes anti-microbial therapy and surgery if necessary.

Anti-Brucella agents are necessary; however, there are no standard regimens regarding the type, dose, and duration of different antibiotics that can be administered to treat this type of infection. Most authors have suggested a minimum duration of antibiotic therapy of 6 weeks. ^{8 , 9} In our case, we prolonged the antibiotic treatment because the symptoms remitted slowly (swelling and pain persisted for the first 5 months after surgery).

Surgical removal of the joint prosthesis is a controversial but usually performed procedure because of the potential risk of relapse of infection. It was performed in 61% of patients who were described in the systematic review of the literature by Kim et al. ⁴

Brucella infection in total joint arthroplasty is an uncommon type of infection that is extremely difficult to diagnose. It is important for physicians to consider this diagnosis in light of every suspicion of prosthesis infection, especially in endemic areas.

The patient was informed and consent to publish clinical data was received for this study. She provided written informed consent to publish this case report.