Excerpt:

We conducted a prospective study to determine causes of acute febrile illness in 4 community hospitals, 2 in Chiang Rai (northern Thailand) and 2 in Khon Kaen (northeastern Thailand). We enrolled patients >7 years of age with a temperature >38°C who were brought to study hospitals for treatment from February 4, 2002, through March 28, 2003. Patients were excluded if they had a history of fever for >2 weeks or an infection that could be diagnosed clinically. Acute-phase serum samples were collected at the time of enrollment and convalescent-phase serum samples 3–5 weeks later. We enrolled nonfebrile control patients >14 years of age who had noninfectious conditions; acute-phase serum samples were collected. Clinical information was abstracted from patient charts. Nurses conducted physical examinations and personal interviews to collect information on patients’ demographic characteristics, exposures to animals, and outdoor activities.

Serum samples were tested for immunoglobulin (Ig) G antibodies to Bartonella spp. by immunofluorescent antibody assay at the Bartonella Laboratory of the Centers for Disease Control and Prevention, Fort Collins, CO, USA. Strains used for antigen production were: B. elizabethae (F9251), B. henselae (Houston-1), B. quintana (Fuller), and B. vinsonii subsp. vinsonii (Baker). Homologous hyperimmune serum specimens were produced in BALB/c mice as previously described (8). Bartonella infection was considered confirmed in febrile patients who had a >4-fold rise in IgG antibody titers and a convalescent-phase titer >64. Probable infection was defined as 1) a 4-fold antibody titer rise but convalescent-phase titers of 64, or 2) high and stable titers (>512 in acute-phase and convalescent-phase serum samples), or 3) acute-phase titer >512 with a >4-fold titer fall. Paired serum samples from febrile patients were also tested for serologic evidence of other common causes of febrile illness in Southeast Asia.

Febrile patients with acute-phase and convalescent-phase IgG antibody titers <128 were considered not to have Bartonella infection; we compared demographic and clinical characteristics of these patients to Bartonella-infected patients. To evaluate potential risk factors, we compared Bartonella-infected case-patients >14 years of age without serologic evidence of other infections (n = 20) to nonfebrile controls with IgG to Bartonella <128 (n = 70). Age adjusted odds ratios (AORs) with 95% confidence intervals (CIs) were calculated.

Benoit VM, Petrich A, Alugupalli KR, Marty-Roix R, Moter A, Leong JM, Boyartchuk VL.

Department of Molecular Genetics and Microbiology, and Program in Gene Function and Expression, University of Massachusetts Medical School, Worcester, MA 01605; Institut für Mikrobiologie und Hygiene, Charité – Universitätsmedizin Berlin, Campus Charité Mitte, 10117 Berlin, Germany; Department of Microbiology and Immunology, Thomas Jefferson University, Philadelphia, PA 19107.

Host susceptibility to infection is controlled in large measure by the genetic makeup of the host. Spirochetes of the genus Borrelia include nearly 40 species of vector-borne spirochetes that are capable of infecting a wide range of mammalian hosts, causing Lyme disease and relapsing fever. Relapsing fever is associated with high-level bacteremia, as well as hematologic manifestations such as thrombocytopenia (i.e. low platelet numbers) and anemia. To facilitate studies of genetic control of susceptibility to Borrelia hermsii infection we performed a systematic analysis of the course of infection using immunocompetent and immunocompromised inbred strains of mice. Our analysis revealed that sensitivity to B. hermsii infections is genetically controlled. In addition, whereas the role of adaptive immunity to relapsing fever spirochetes is well documented, we found that innate immunity contributes significantly to reduction of bacterial burden. Similar to human infection, progression of the disease in mice was associated with thrombocytopenia and anemia. Histological and fluorescence in situ hybridization (FISH) analysis of infected tissues indicated that red blood cells were removed by tissue resident macrophages, a process that could lead to anemia. Spirochetes in the spleen and liver were often visualized associated with RBCs, lending support to the hypothesis that direct interaction of B. hermsii spirochetes with RBCs leads to clearance of bacteria from the bloodstream by tissue phagocytes.

PMID: 19995898 [PubMed – as supplied by publisher]