Diagnosis of 22 new cases of Bartonella endocarditis

Background: Bartonella species are emerging pathogens that are seldom reported as a cause of blood culture-negative endocarditis. Objective: To report the occurrence of, risk factors for, and clinical features of Bartonella endocarditis and to evaluate the diagnostic tools available for this condition. Design: Case series and comparison with past series. Setting: Multicenter international study in Halifax, Nova Scotia, Canada; Lyon, France; and Marseille, France. Patients: 22 patients from France, England, Canada, and South Africa were investigated for blood culture-negative endocarditis. Measurements: Titer of antibodies to Bartonella species by microimmunofluorescence assay, blood or vegetation culture, and amplification of Bartonella DNA from valvular tissue by polymerase chain reaction. Cross-adsorption was done for patients with antibodies to Chlamydia species. Results: 22 patients had definite endocarditis. Five were infected with B. quintana, 4 with B. henselae, and 13 with an undetermined Bartonella species. These cases were compared with the 11 previously reported cases. Of the patients with the newly reported cases, 19 had valvular surgery and 6 died. Nine were homeless, 11 were alcoholic, 4 owned cats, and 13 had preexisting valvular heart disease. Bartonella species caused 3% of the cases of endocarditis seen in the three study centers. The patients with these cases could have previously received a diagnosis of chlamydial endocarditis because of apparently high levels of cross-reacting antibodies to Chlamydia species. Conclusions: Bartonella species are an important cause of blood culture-negative endocarditis and can be identified by culture, serologic studies, or molecular biology techniques. Alcoholism and homelessness without previous valvular heart disease are risk factors for B. quintana infection but not for infection with other Bartonella species.