Antibiotics guided by metagenomic next-generation sequencing to control infection after total knee arthroplasty: A case report and literature review.

RATIONALE: A prosthetic joint infection is a serious complication of joint surgery, with Staphylococcus aureus being the most common pathogen. In contrast, C. burnetii, the agent of Q fever, is a rare zoonotic parasite primarily found in cattle and sheep. It can be transmitted through respiratory, digestive, and cutaneous routes, destroying host cells and leading to diseases such as bone and joint infections, endocarditis, and interstitial lung disease.

PATIENT CONCERNS: A 75-year-old male patient underwent total knee arthroplasty due to degenerative disease in his left knee. After surgery, he was exposed to cattle and their feces. Fifteen months after the operation, he experienced pain, though there was no significant elevation of erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and white blood cell (WBC). Oral nonsteroidal anti-inflammatory drugs (NSAIDs) were administered. The pain intensified and was accompanied by swelling. ESR and CRP were elevated, while WBC remained normal. The patient took oral Rifampicin for 28 days without improvement. The knee joint puncture culture was negative. The metagenomic next-generation sequencing (mNGS) detected C. burnetii, and oral Doxycycline for 1 week. The intravenous infusion of Doxycycline and Moxifloxacin continued for 28 days. After the above indexes stabilized, a 1-stage revision surgery was performed, and Doxycycline and Moxifloxacin were administered for 16 days until the indexes returned to normal and symptoms such as knee joint pain and swelling disappeared.

DIAGNOSES: Left knee radiography, laboratory tests, and knee cavity puncture, culture, and mNGS testing were performed to confirm the diagnosis of the pathogen.

INTERVENTIONS: According to mNGS, the left knee was revised and antibiotics were applied before and after the operation until the infection indexes returned to normal and symptoms such as knee pain and swelling disappeared.

OUTCOMES: ESR, CRP, and WBC indexes were normal. Pain and swelling disappeared. Other symptoms disappeared. Joint flexion and extension mobility was good.

LESSONS: In patients with postoperative prosthetic joint infection after total knee arthroplasty, mNGS can identify pathogenic bacteria, inform the use of antibiotics, and enable prompt surgical intervention.