Detection of zoonotic Coxiella burnetii causing chronic Q fever endocarditis in a Chinese geriatric patient by mNGS.

OBJECTIVE

Q (query) fever, caused by Coxiella burnetii, is often linked to negative bacterial cultures, with infective endocarditis with negative cultures difficult to diagnose and treat. Our case demonstrates that metagenomic next-generation sequencing (mNGS) is able to provide a rapid and accurate method for pathogenetic diagnosis in infectious diseases.

CASE PRESENTATION: A case of infective endocarditis with negative blood cultures is reported in a male patient with a history of sheep farming and previous aortic valve replacement and atrial septal defect atrial septal defect repair. Blood tests showed positive serum immunofluorescent antibodies to Rickettsia, while mNGS of perivalvular abscess tissue suggested C. burnetii. Doxycycline 0.1 g q12h and hydroxychloroquine 0.2 g q12h were used for postoperative antibiotic treatment. The genome of C. burnetii C2245173Z was assembled on the Illumina platform and no known antibiotic resistance genes were detected. Phylogenetic analysis of the C. burnetii genome showed a genetic relationship between animal- and human-derived strains.

CONCLUSIONS

mNGS could provide a rapid and accurate assay for clinical diagnosis and play a decisive role in the pathogenetic diagnosis of some infectious diseases. Doxycycline plus hydroxychloroquine remains an effective treatment for chronic Q fever endocarditis. In addition, phylogenetic tree analysis indicates that C. burnetii infection may pose a potential risk to humans working with livestock.