Bartonella endocarditis: lessons learnt from an African cohort

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Abstract Background Bartonella (B) quintana endocarditis is a preventable, vector-borne, and important cause of blood culture-negative endocarditis (BCNE). The ESC guideline for the management of endocarditis recommends blood serology (IgG titer ≥800) and polymerase chain reaction (PCR) testing on both blood and valvular tissue for diagnosis. Access to these molecular technologies is limited in Africa and there is a paucity of B. quintana endocarditis research on the continent. Purpose Record the clinical picture and explore the risk factors for disease and the diagnostic utility of immunofluorescence (IFA) in PCR-proven cases with B. quintana endocarditis. Methods Data were analysed from a prospective observational cohort study of patients with infective endocarditis managed at our institution. All BCNE cases from October 2019 to January 2024 were evaluated to identify patients with PCR-proven B. quintana on valvular tissue. A commercially available IFA was used for blood serology testing. 16S rRNA PCR testing with sequencing was performed on valvular tissue. Results Thirty five of the 58 cases (60.3%) with BCNE were diagnosed with Bartonella endocarditis. A diagnosis of PCR-proven B. quintana endocarditis was made in 21 cases. Of these, seven patients (33.3%) were either homeless or lived in informal housing. Thirteen patients (61.9%) had an alcohol-use disorder. Four patients (19%) were Human Immunodeficiency (HIV) virus- positive. Eighteen patients (85.7%) reported the onset of symptoms more than two weeks before presentation. Common presenting symptoms were dyspnea (n=21;100%), loss of weight (n=10;47.6%) and fever (n=7;33.3%). Common clinical features were digital clubbing (n=17;80.9%), pallor (n=13; 61.9%), microscopic haematuria (n=12; 57.1%) and severe regurgitant lesions (n=21; 100%). Blood serology was available in 17 patients with an IgG titer (1≥256) in all patients apart from one (1:64). Only one case (5.8%) had an IgG titre ≥800. The most common isolated valve lesion on echocardiography was severe aortic regurgitation (n=10;47.6%). Surgical replacement and repair were performed in 17(80.9%) and 4(19%) patients respectively. The one-, three- and six-month mortality was 14%, 14 % and 14% respectively. No cases of relapse were reported. Discussion B.quintana is the most prevalent cause of BCNE in our centre. The typical clinical and echocardiographic profile was consistent with the reported literature of a destructive endocarditis in a patient with a low socioeconomic background. Despite this, the surgical outcome is fair and comparable to European data. The IFA used in this study is different to the assay referenced in the ESC guideline and may explain the relatively low serology titres observed (despite PCR-proven disease). Further study with the commercial IFA is needed to determine a cut-off titre that will give a comparable sensitivity to the referenced in-house IFA.Destructive aortic valve endocarditisResultant severe aortic regurgitation