Chronic prosthetic joint infection caused by Coxiella burnetii diagnosed by metagenomic next-generation sequencing: A case report and literature review.

Prosthetic joint infection (PJI) caused by Coxiella burnetii (C. burnetii) remains a rare but clinically significant diagnostic challenge due to its culture-negative characteristics and nonspecific clinical manifestations. Metagenomic next-generation sequencing (mNGS) has emerged as a valuable tool for identifying fastidious pathogens in culture-negative PJI cases. A patient with a history of joint arthroplasty presented with persistent joint pain and swelling. Despite multiple surgical interventions and prolonged empirical antibiotic therapy, routine bacterial cultures remained negative and the infection recurred. mNGS performed on periprosthetic tissue detected C. burnetii in two independent specimens, while all conventional cultures remained negative. Targeted antimicrobial therapy with doxycycline combined with levofloxacin was initiated, resulting in gradual symptom resolution and sustained clinical improvement during follow-up. This case highlights C. burnetii as an underrecognized cause of culture-negative PJI and demonstrates the clinical value of mNGS for early pathogen identification when conventional diagnostics fail. Repeated detection in independent specimens strengthened diagnostic confidence and enabled timely targeted therapy. Our findings support the early incorporation of mNGS into the diagnostic algorithm for suspected culture-negative PJI. In the present case, targeted doxycycline-levofloxacin therapy following mNGS-based pathogen identification was associated with sustained clinical improvement.