Bartonella quintana Bloodstream Infection in A Patient Newly Diagnosed with Dermatomyositis: A Case Report Highlighting The Medical Relevance of Molecular Metagenome Analysis

Background: The clinical presentation of patients suffering from Bartonella quintana infection is highly variable, ranging from an asymptomatic to a fulminant course of the disease. Most patients present with a febrile episode, which is frequently indicative of recurrence. Due to the pathogen´s ability to employ multiple evasion strategies, chronic bacteremia may persist for an extended duration. The fastidious growth behaviour of Bartonella quintana represents a significant challenge to its identification by traditional microbiological techniques. Consequently, a failure to detect an infection may result in misdiagnosis and inappropriate treatment. Case Presentation: Here, we present a case of Bartonella quintana infection with unusual disease manifestation, as the subacute onset coincided with a newly diagnosed dermatomyositis. In addition to a generalized myopathy, the patient presented with a prolonged subfebrile phase, which however developed after hospitalization. Since several blood cultures turned positive, cultivation of the pathogen proved difficult due to prolonged growth time. Although biochemical identification failed, serological testing provided preliminary evidence of a Bartonella infection. Nevertheless, the definitive diagnosis of Bartonella quintana bacteremia was obtained by 3rd generation sequencing of positive blood cultures. In accordance with Duke´s criteria, these findings were consistent with the possible presence of endocarditis. The combination of anti-inflammatory and prolonged doxycycline therapy was highly effective, leading to a rapid regression of the patient´s clinical symptoms. Conclusions: Identification of Bartonella quintana infections by traditional microbiological methods remain challenging. Novel molecular approaches such as 3rd generation sequencing may contribute to the rapid detection of pathogens, thereby promoting an earlier targeted therapy.