Acute Q Fever After Diabetic Ketoacidosis Correction: Repeated Blood Targeted Next-Generation Sequencing and Antimicrobial De-Escalation

Abstract

Background Acute Q fever caused by Coxiella burnetii is often missed because clinical manifestations are nonspecific, routine cultures are unrevealing, and typical zoonotic exposure may be absent. Persistent fever after correction of diabetic ketoacidosis (DKA) should prompt reassessment for atypical or intracellular pathogens. Case Presentation A 56-year-old man with type 2 diabetes mellitus was admitted with polyuria, polydipsia, and DKA but was afebrile and had no obvious infectious symptoms on admission. Metabolic acidosis resolved within 24 hours, but persistent high-grade fever subsequently developed. Imaging, urinalysis, transthoracic echocardiography, conventional pathogen testing, and two separate aerobic and anaerobic blood-culture sets did not identify a definite infectious focus. Two independent peripheral blood targeted next-generation sequencing (tNGS) assays detected high-abundance C. burnetii with 92,895 and 24,341 reads, respectively. Doxycycline was initiated after the first tNGS report, and meropenem was discontinued after repeat tNGS supported reproducible detection. The patient denied livestock exposure, tick bite, cat or dog contact, relevant occupational exposure, recent travel, and ingestion of raw milk or raw animal products. Paired serology showed a fourfold rise in Phase II IgG titer from 1:128 to 1:512, supporting acute Q fever. Conclusion Repeated peripheral blood tNGS can provide actionable etiological evidence for acute Q fever presenting as persistent fever after DKA correction. When interpreted with clinical features and paired serology, tNGS may support antimicrobial de-escalation from intravenous broad-spectrum carbapenem therapy to pathogen-directed oral doxycycline.