Bartonella Infections in Sweden: Clinical Investigations and Molecular Epidemiology

Sammanfattning: Characteristically, in infections that are caused by the zoonotic pathogen Bartonella naturally infected reservoir hosts are asymptomatic, where infected incidental, non-natural, hosts develop symptomatic disease. Cat-scratch disease (CSD) is a well known example. Bartonella infections in humans may be self-limiting or fulminant and affect different organ systems.The objectives of the present thesis were to (1) identify and characterise Bartonella infection cases in Sweden, (2) to investigate certain human populations regarding Bartonella infections, and (3) compare natural populations of different Bartonella species.Cases with typical and atypical CSD were recognised by using a combination of PCR and serology. Gene sequence comparisons of different genes in B. henselae isolates from the United States and Europe showed that ftsZ gene variation is a useful tool for Bartonella genotyping.Myocarditis was a common finding among Swedish elite orienteers succumbing to sudden unexpected cardiac death (SUCD). The natural cycle of Bartonella spp., the life style of orienteers, elevated antibody titres to Bartonella antigens, Bartonella DNA amplified from myocardium and the lack of another feasible explanation make Bartonella a plausible aetiological factor.The first reported case of Bartonella endocarditis (B. quintana) was identified in an immunocompromised patient who underwent heart valve replacement. The patient had been body louse-infested during his childhood. It is hypothesised that a chronic B. quintana infection was activated by the immunosuppression.There was no evidence of an ongoing trench fever (TF) epidemic in a Swedish homeless population, although an increased risk for exposure to Bartonella antigens was demonstrated. The lack of louse infestation might explain the absence of B. quintana bacteremia and low B. quintana antibody titres.Comparisons of genetic loci and the whole genomes of environmental B. grahamii isolates from the Uppsala region, Sweden displayed variants that were not related to specific host species but to geographic locality. Natural boundaries seemed to restrict gene flow.