Bartonella species cause serious human infections globally, including bacillary angiomatosis, Oroya fever, trench fever, and endocarditis. We describe a patient who had fever and splenomegaly after traveling to Peru and also had bacteremia from an organism that resembled Bartonella bacilliformis, the causative agent of Oroya fever, which is endemic to Peru. However, genetic analyses revealed that this fastidious bacterium represented a previously uncultured and unnamed bartonella species, closely related to B. clarridgeiae and more distantly related to B. bacilliformis. We characterized this isolate, including its ability to cause fever and sustained bacteremia in a rhesus macaque. The route of infection and burden of human disease associated with this newly described pathogen are currently unknown.

Bartonella quintana is a fastidious, gram-negative, rod-shaped bacterium that causes prolonged bacteremia in immunocompetent humans and severe infections in immunocompromised individuals. We sought to define the outer membrane subproteome of B. quintana in order to obtain insight into the biology and pathogenesis of this emerging pathogen and to identify the predominant B. quintana antigens targeted by the human immune system during infection. We isolated the total membrane proteins of B. quintana and identified 60 proteins by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and peptide mass fingerprinting. Using the newly constructed proteome map, we then utilized two-dimensional immunoblotting with sera from 21 B. quintana-infected patients to identify 24 consistently recognized, immunoreactive B. quintana antigens that have potential relevance for pathogenesis and diagnosis. Among the outer membrane proteins, the variably expressed outer membrane protein adhesins (VompA and VompB), peptidyl-prolyl cis-trans-isomerase (PpI), and hemin-binding protein E (HbpE) were recognized most frequently by sera from patients, which is consistent with surface expression of these virulence factors during human infection.Bartonella quintana, the agent of trench fever, is a fastidious, gram-negative, rod-shaped organism that can cause prolonged bacteremia in immunocompetent humans and severe infections in immunocompromised individuals. Humans are the only known reservoir for B. quintana (12), and the vector for transmission is the human body louse, Pediculus humanus corporis (38). B. quintana infections have occurred worldwide, and severe, potentially lethal complications, such as endocarditis and bacillary angiomatosis, can develop in immunocompromised patients with AIDS, cancer, and organ transplants. However, little is known about the pathogenesis of B. quintana, and diagnosis of human infection remains extremely challenging. To address this paucity of knowledge, we sought to identify potential membrane-associated virulence factors, as well as protective and diagnostically relevant B. quintana antigens, by characterizing the total membrane fraction and immunome of B. quintana.Bacterial outer membrane proteins (OMP) can be important virulence factors, playing a critical role in adherence, invasion, and immune evasion during infection of the host, as well as during transmission via arthropod vectors. Many outer membrane-associated proteins that are important for pathogenesis also are consistent targets for the host immune system after infection. Workers in our lab previously identified a family of variably expressed outer membrane proteins (Vomp) that play a role in adhesion and autoaggregation (45). To initially identify the Vomp family, we used two-dimensional (2D) sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE) to visualize changes in expression of membrane proteins in sequential isolates from animals experimentally infected with B. quintana.To identify additional membrane pr...

Bartonella bacteria adhere to erythrocytes and persistently infect the mammalian bloodstream. We previously identified four highly conserved Bartonella quintana adhesin genes that undergo phase variation during prolonged bloodstream infection. The variably expressed outer membrane proteins (Vomp) encoded by these genes are members of the trimeric autotransporter adhesin family. Each B. quintana Vomp appears to contribute a different adhesion phenotype, likely mediated by the major variable region at the adhesive tip of each Vomp. Although studies document that the Vomp adhesins confer virulence phenotypes in vitro, little is known about in vivo virulence strategies of Bartonella. We sought to determine whether the B. quintana Vomp adhesins are necessary for infection in vivo by using a vomp null mutant. It first was necessary to develop a system to generate in-frame deletions of defined genes by allelic exchange in a wild-type Bartonella background, which had not been achieved previously. We utilized sacB negative selection to generate a targeted, in-frame, markerless deletion of the entire vomp locus in B. quintana. We also recently developed the first animal model for B. quintana infection, and using this model, we demonstrate here that the deletion of the entire vomp locus, but not the deletion of two vomp genes, results in a null mutant strain that is incapable of establishing bloodstream infection in vivo. The Vomp adhesins therefore represent critical virulence factors in vivo, warranting further study. Finally, our allelic exchange strategy provides an important advance in the genetic manipulation of all Bartonella species and, combined with the animal model that recapitulates human disease, will facilitate pathogenesis studies of B. quintana.Bartonella species are fastidious, gram-negative bacteria that persistently infect the bloodstream of many mammals. The three major Bartonella pathogens infecting humans are Bartonella quintana, B. henselae, and B. bacilliformis. B. quintana is transmitted by the human body louse and causes relapsing fever ("trench fever"), endocarditis, and the highly vascular lesions of bacillary angiomatosis (13). Bacteremia can persist for months, and unsuspected bloodstream infection with Bartonella can be detected in 5 to 14% of asymptomatic individuals in certain geographic regions (6, 27). B. quintana can cause debilitating, even fatal, illness in immunocompromised individuals with cancer, transplanted organs, or AIDS.Phase and antigenic variation are immune response-evading virulence strategies exploited by microbial pathogens to persist in a host (3). We identified a family of B. quintana proteins that appears to undergo phase variation (28). These surface-localized adhesins, designated Vomp (variably expressed outer membrane proteins), are variably expressed over the course of prolonged bloodstream infection in vivo and are encoded by four highly conserved, tandemly arranged genes (28). These genes, vompD, vompA, vompB, and vompC, are located on a 12.8-kb region of the B. ...

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