Abstract
Background
Conventional diagnosis of infective endocarditis (IE) is based mainly on culture-dependent methods that may fail because of antibiotic therapy or fastidious microorganisms.
Objectives
We aimed to evaluate the added values of serological and molecular methods for diagnosis of infective endocarditis.
Patients and methods
One hundred and fifty-six cases of suspected endocarditis were enrolled in the study. For each patient, three sets of blood culture were withdrawn and serum sample was collected for
Brucella
,
Bartonella
and
Coxiella burnetii
antibody testing. Galactomannan antigen was added if fungal endocarditis was suspected. Broad range PCR targeting bacterial and fungal pathogens were done on blood culture bottles followed by sequencing. Culture and molecular studies were done on excised valve tissue when available.
Results
One hundred and thirty-two cases were diagnosed as definite IE. Causative organisms were detected by blood cultures in 40 (30.3 %) of cases. Blood culture-negative endocarditis (BCNE) represented 69.7 %. Of these cases, PCR followed by sequencing on blood and valvular tissue could diagnose five cases of
Aspergillus flavus
. Eleven patients with BCNE (8.3 %) were diagnosed as zoonotic endocarditis by serology and PCR including five cases of
Brucella
spp, four cases of
Bartonella
spp and two cases of
Coxiella burnetii
. PCR detected three cases of
Brucella
spp and two cases of
Bartonella
spp, while cases of
Coxiella burnetii
were PCR negative. The results of all diagnostic tools decreased the percentage of non-identified cases of BCNE from 69.7 to 49.2 %.
Conclusion
Our data underline the role of serologic and molecular tools for the diagnosis of blood culture-negative endocarditis.