Diagnosis of Coxiella burnetii Prosthetic Joint Infection Using mNGS and ptNGS: A Case Report and Literature Review

BACKGROUND: Coxiella burnetii (C. burnetii) is the causative agent of Q fever and is found worldwide; however, prosthetic joint infections caused by C. burnetii are rarely seen. Because of advances in molecular diagnostic techniques, prosthetic joint infection (PJI) caused by C. burnetii can now be diagnosed. CASE PRESENTATION: A 77‐year‐old male who had undergone total knee arthroplasty had a displaced prosthesis and periprosthetic osteolysis; he had no obvious signs of infection, and microbiological culture was negative. However, C. burnetii was detected by metagenomic next‐generation sequencing (mNGS) and pathogen‐targeted next‐generation sequencing (ptNGS). Finally, polymerase chain reaction (PCR) confirmed the diagnosis of C. burnetii prosthetic joint infection (PJI). After revision surgery (one‐stage revision) and oral antibiotics (doxycycline and moxifloxacin hydrochloride), the patient's symptoms disappeared, and he regained the ability to walk. During the 6‐month follow‐up, the patient's knee showed no signs of swelling, pain or the recurrence of infection, and he experienced no significant complications. We also present a review of the literature for other cases of C. burnetii PJI. CONCLUSIONS: The symptoms of C. burnetii PJI may be different from those of Q fever, which may lead to misdiagnosis. mNGS and ptNGS may be helpful for the identification of C. burnetii. Once the diagnosis of C. burnetii PJI is confirmed, doxycycline in combination with a fluoroquinolone can be effectively administered after revision surgery.