Multispacer sequence typing of Coxiella burnetii DNA from removed prosthetic heart valve material discloses first human case of infective endocarditis caused by MST_18

Introduction: In Denmark, Q fever has previously been considered a rare and imported disease; however, recent testing of antibodies in cattle as well as humans has indicated that the infection is widespread. A 76-year-old Danish man was diagnosed with infective endocarditis and underwent open surgical aortic valve replacement with insertion of a biological valve. Due to paravalvular leakage, destruction of the aortic annulus, and an aortic root abscess, the patient underwent re-operation 3 weeks later, with replacement of the biological valve and insertion of an aortic prosthetic tube. Despite treatment with various broad-spectrum antibiotic regimes, the patient died 3.5 months after initial hospital admission. Methods: The causative agent was probed by PCR amplification of bacterial DNA on the removed prosthetic aortic valve using broad range primers targeting the variable regions V1–V3 of the 16S RNA gene. After identification of Coxiella burnetii, multispacer sequence typing (MST) was performed by PCR amplification of 10 intergenic sequences. Results: BLAST analysis of DNA from prosthetic valve material identified a 16S rRNA gene fragment almost identical to the type strain of C. burnetii (462/463 nt). Molecular typing allocated the strain to MST_18. Conclusions: Molecular methods are increasingly used to characterize isolates and to determine relationships between isolates that cause disease in different contexts and geographical areas. The present case demonstrates that identification and typing of C. burnetii is achievable without access to biosafety level 3 containment and highlights the first molecular characterization of an uncultured strain of C. burnetii causing infective endocarditis. Keywords: Q fever, Coxiella burnetii, Culture-negative infective endocarditis, Multispacer sequence typing, 16S rRN