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PubMed2003

Randomized open trial of gentamicin and doxycycline for eradication of Bartonella quintana from blood in patients with chronic bacteremia.

Chronic Bartonella quintana bacteremia is known to occur in homeless people exposed to lice. We present here the results of an open randomized trial performed to evaluate the efficacy of doxycycline in combination with gentamicin in the eradication of B. quintana bacteremia. From 1 January 2001 to 1 April 2002, homeless people with blood cultures positive for B. quintana were randomized to receive either no treatment (untreated controls) or a combination of gentamicin (3 mg/kg of body weight/day intravenously for 14 days) and doxycycline (200 mg/day orally for 28 days). Patients were evaluated from the results of blood cultures performed between day 28 (the end of treatment) and day 90 postinclusion. Intention-to-treat analysis of 20 included patients showed eradication of bacteremia in 7 out of 9 treated patients versus 2 out of 11 untreated controls (P = 0.01). In the per-protocol analysis, eradication was obtained for 7 out of 7 treated patients versus 2 out of 9 untreated controls (P = 0.003). This study demonstrates the efficiency of the combination of doxycycline and gentamicin in eradicating B. quintana bacteremia.

Adult↗
PubMed2004

Growth characteristics of Bartonella henselae in a novel liquid medium: primary isolation, growth-phase-dependent phage induction, and metabolic studies.

Bartonella henselae is a zoonotic pathogen that usually causes a self-limiting infection in immunocompetent individuals but often causes potentially life-threatening infections, such as bacillary angiomatosis, in immunocompromised patients. Both diagnosis of infection and research into the molecular mechanisms of pathogenesis have been hindered by the absence of a suitable liquid growth medium. It has been difficult to isolate B. henselae directly from the blood of infected humans or animals or to grow the bacteria in liquid culture media under laboratory conditions. Therefore, we have developed a liquid growth medium that supports reproducible in vitro growth (3-h doubling time and a growth yield of approximately 5 x 10(8) CFU/ml) and permits the isolation of B. henselae from the blood of infected cats. During the development of this medium, we observed that B. henselae did not derive carbon and energy from the catabolism of glucose, which is consistent with genome nucleotide sequence data suggesting an incomplete glycolytic pathway. Of interest, B. henselae depleted amino acids from the culture medium and accumulated ammonia in the medium, an indicator of amino acid catabolism. Analysis of the culture medium throughout the growth cycle revealed that oxygen was consumed and carbon dioxide was generated, suggesting that amino acids were catabolized in a tricarboxylic acid (TCA) cycle-dependent mechanism. Additionally, phage particles were detected in the culture supernatants of stationary-phase B. henselae, but not in mid-logarithmic-phase culture supernatants. Enzymatic assays of whole-cell lysates revealed that B. henselae has a complete TCA cycle. Taken together, these data suggest B. henselae may catabolize amino acids but not glucose to derive carbon and energy from its host. Furthermore, the newly developed culture medium should improve isolation of B. henselae and basic research into the pathogenesis of the bacterium.

Angiomatosis, Bacillary↗
PubMed2003

Detection by immunofluorescence assay of Bartonella henselae in lymph nodes from patients with cat scratch disease.

Laboratory diagnosis of Bartonella henselae infections can be accomplished by serology or PCR assay on biopsy samples. The purpose of our work was to assess immunofluorescence detection (IFD) in lymph node smears using a specific monoclonal antibody directed against B. henselae and a commercial serology assay (IFA) compared with PCR detection. Among 200 lymph nodes examined from immunocompetent patients, 54 were positive for B. henselae by PCR, of which 43 were also positive by IFD. Among the 146 PCR-negative lymph nodes, 11 were positive by IFD. Based on PCR results, the specificity of this new technique was 92.5%, the sensitivity was 79.6%, and the positive predictive value was 79.6%. At a cutoff titer of 64, the sensitivity of the IFA was 86.8% and the specificity was 74.1%. Diagnosis of cat scratch disease (CSD) may be improved, with a specificity of 100%, when the two tests (IFD and IFA) were negative; the sensitivity was 97.4% if one of the two tests was positive. Since PCR-based detection with biopsy samples is available only in reference laboratories, we suggest using IFD coupled with the commercial serology test for the diagnosis of CSD.

Adolescent↗
PubMed1995

Intracellular location of Bartonella henselae cocultivated with Vero cells and used for an indirect fluorescent-antibody test.

Bartonella henselae, the major causative agent of cat scratch disease, was cocultivated with Vero cells on chamber slides and visualized by indirect immunofluorescence by using a patient serum containing specific antibodies. Confocal microscopy localized the granular B. henselae-specific fluorescence mainly around the nuclei of Vero cells. By transmission electron microscopy, these granules were identified as clusters of multiple intracellular organisms. Fixed slides with the monolayers of Vero cells with intracellular B. henselae were used for an indirect fluorescent-antibody test to investigate the seroprevalence of specific immunoglobulin G in 100 serum samples from blood donors. Seventy-four serum samples were negative; 19, 3, and 4 were positive at dilutions of 1:64, 1:128, and 1:256, respectively. In our population, a serum titer of 1:256 or greater should stimulate further investigations. Moreover, elucidation of the mechanism by which B. henselae enters the cells may help to understand the pathogenesis of cat scratch disease.

Animals↗
PubMed1996

Diagnostic value of the indirect immunofluorescence assay in cat scratch disease with Bartonella henselae and Afipia felis antigens.

Serum samples from 35 cat scratch disease (CSD) patients, 180 control patients (123 without lymph node enlargement and 57 with lymph node enlargement not evoking CSD), and 102 nonpatient subjects (35 with cat contact and 67 without cat contact) were tested by semiquantitative indirect immunofluorescence assay for the presence of antibodies directed to Afipia felis (ATCC 53690T) or Bartonella henselae (ATCC 49882T). The CSD group had statistically higher antibody titers against B. henselae than the control groups (P < 10(-5)), whereas no difference in A. felis antibody titers was evidenced among all groups tested. Among the 317 serum samples studied, the three with high A. felis antibody titers ( > or = 64) also had high antibody titers against other alpha-2 proteobacteria. The value of the indirect immunofluorescence assay with B. henselae antigen for the diagnosis of CSD was as follows: for a cutoff of 32, sensitivity was 0.80, specificity was 0.85, and the likelihood ratio was 5.1; for a cutoff of 64, the likelihood ratio was 12.1. In summary, in France, CSD is associated with high antibody titers against B. henselae, as previously described in the United States. However, the causes for B. henselae seronegativity in CSD patients and those for high antibody titers outside the typical nosological frame of CSD still have to be identified.

Adult↗
PubMed2006

Environmental signals generate a differential and coordinated expression of the heme receptor gene family of Bartonella quintana.

Of all bacteria, Bartonella quintana has the highest reported in vitro hemin requirement, yet an explanation for this remains elusive. To produce diseases such as trench fever, endocarditis, and bacillary angiomatosis, B. quintana must survive and replicate in the disparate environments of the Pediculus humanus corporis (body louse) gut and the human vasculature. We previously identified a five-member family of hemin binding proteins (Hbps) synthesized by B. quintana that bind hemin on the outer surface but share no similarity to known bacterial heme receptors. In the present study, we examine the transcription, regulation, and synthesis of this virulence factor family by cultivation of the bacterium in environments that simulate natural heme, oxygen, and temperature conditions encountered in the host and insect vector. First, quantitative real-time PCR data show that hbpC expression is regulated by temperature, where a >100-fold increase in transcript quantity was seen at 30 degrees C relative to 37 degrees C, suggesting that HbpC synthesis would be greatest in the cooler temperature of the louse. Second, cultivation at human bloodstream oxygen concentration (5% relative to 21% atmospheric) significantly decreases the transcript quantity of all hbp genes, indicating that expression is influenced by O2 and/or reactive oxygen species. Third, a differential expression pattern within the hbp family is revealed when B. quintana is grown in a range of hemin concentrations: subgroup I (hbpC and hbpB) predominates in a simulated louse environment (high heme), and subgroup II (hbpA, hbpD, and hbpE) is preferentially expressed in a simulated human background (low heme). By using two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoblotting, and matrix-assisted laser desorption ionization-time of flight mass spectrometry fingerprinting, we demonstrate that synthesis of HbpA correlates with hbpA transcript increases observed at low hemin concentrations. Finally, an hbpA promoter-lacZ reporter construct in B. quintana demonstrates that a transcriptional regulator(s) is controlling the expression of hbpA through a cis-acting regulatory element located in the hbpA promoter region.

Bartonella quintana↗
PubMed2006

Autocrine role for interleukin-8 in Bartonella henselae-induced angiogenesis.

The gram-negative bacterium Bartonella henselae is capable of causing angiogenic lesions as a result of infection. Previously, it has been shown that B. henselae infection can result in production of the chemokine interleukin-8 (IL-8). In this study, we demonstrated that monocytes, endothelial cells, and hepatocytes produce IL-8 in response to B. henselae infection. We also investigated the role of IL-8 in B. henselae-induced endothelial cell proliferation and capillary tube formation. Both in vitro angiogenesis assays were IL-8 dependent. B. henselae-mediated inhibition of apoptosis, as indicated by gene expression of Bax and Bcl-2, was also shown to be IL-8 dependent in endothelial cells. Furthermore, infection of endothelial cells with B. henselae stimulated upregulation of the IL-8 chemokine receptor CXCR2. Infection of human endothelial cells by B. henselae resulting in IL-8 production likely plays a central role in the ability of this organism to cause angiogenesis during infection.

Angiomatosis, Bacillary↗
PubMed2006

Bartonella quintana variably expressed outer membrane proteins mediate vascular endothelial growth factor secretion but not host cell adherence.

Bartonella quintana causes trench fever, endocarditis, and the vasculoproliferative disorders bacillary angiomatosis and peliosis hepatis in humans. Little is known about the interaction of this pathogen with host cells. We attempted to elucidate the interaction of B. quintana with human macrophages (THP-1) and epithelial cells (HeLa 229). Remarkably, only B. quintana strain JK-31 induced secretion of vascular endothelial growth factor (VEGF) from THP-1 and HeLa 229 cells upon infection similar to the secretion induced by B. henselae Marseille, whereas other strains (B. quintana 2-D70, B. quintana Toulouse, and B. quintana Munich) did not induce such secretion. Immunofluorescence testing and electron microscopy revealed that the B. quintana strains unable to induce VEGF secretion did not express the variable outer membrane proteins (Vomps) on their surfaces. Surprisingly, the increase in VEGF secretion mediated by B. quintana JK-31 was not paralleled by elevated host cell adherence rates compared with the rates for Vomp-negative B. quintana strains. Our results suggest that the Vomps play a leading role in the angiogenic reprogramming of host cells by B. quintana but not in the adherence to host cells.

Amino Acid Sequence↗
PubMed1986

Entry of Bartonella bacilliformis into erythrocytes.

Bartonella bacilliformis, which causes the human diseases Oroya fever and verruga peruana, binds to human erythrocytes in vitro and produces substantial and long-lasting deformations in erythrocyte membranes, including cone-shaped depressions, trenches, and deep invaginations. The deforming force is probably provided by the polar flagella of these highly motile bacteria. Deep invaginations containing bacteria are commonly seen, and membrane fusion at the necks of the invaginations leads to the formation of intracellular vacuoles containing bacteria. Fluorescent compounds present externally render the vacuoles fluorescent and, occasionally, lightly fluorescent cells are seen, suggesting that the vacuoles sometimes rupture to admit the bacteria to the cytoplasm. Vacuoles present in fluorescent erythrocytes prepared by preloading the erythrocytes with fluorescent compounds are seen as dark areas from which the fluorescent marker is excluded. Entry of the bacteria appears to be the result of a process of forced endocytosis.

Bacterial Adhesion↗
PubMed1992

Deformation factor: an extracellular protein synthesized by Bartonella bacilliformis that deforms erythrocyte membranes.

Bartonella bacilliformis, a hemotropic bacterium and the causative agent of the human disease bartonellosis, when incubated in a tryptone-based medium produces an extracellular factor, termed deformation factor (DF), which induces extensive indentations and trenches in trypsinized erythrocyte membranes. The factor is stable during storage at 4 degrees C. It can be inactivated by proteases or brief heating to 70 to 80 degrees C, can be precipitated by ammonium sulfate, is nondialyzable, and is retained by membranes with a 30,000-molecular-weight cutoff. These properties suggest that DF is probably a protein. Incubation of erythrocytes with phospholipase D renders them resistant to deformation by DF.

Animals↗
PubMed1995

Characterization of a two-gene locus from Bartonella bacilliformis associated with the ability to invade human erythrocytes.

Bartonella bacilliformis, the agent of human Oroya fever, invades erythrocytes and causes a severe hemolytic anemia. The ability of two minimally invasive strains of Escherichia coli (DH5 alpha and HB101) to invade human erythrocytes was enhanced 6- to 39-fold by transformation with pIAL1, a plasmid containing a 1,469-bp BamHI fragment from the B. bacilliformis chromosome. Invasiveness was confirmed by gentamicin protection and transmission electron microscopy. DNA hybridization analysis confirmed the presence of the locus in B. bacilliformis KC583 and KC584 and its absence in E. coli chromosomal DNA. Sequencing of the DNA insert of pIAL1 revealed tandem open reading frames of 510 and 558 bp, designated ialA and ialB, respectively. Invasion assays with E. coli containing only an ialA or ialB recombinant suggest that both genes are necessary for invasiveness. The ialA gene is predicted to code for a polypeptide of 170 amino acids (20.1 kDa), and ialB is predicted to code for a polypeptide of 186 amino acids (19.9 kDa). In vitro transcription and translation of pIAL1 produced insert-specific protein bands with masses of approximately 21 and 20 kDa when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Expression of ialA and ialB in E. coli maxicells produced proteins with masses of approximately 21 kDa (IalA) and 18 kDa (IalB). Maxicell and computer analyses suggest that IalB contains an N-terminal secretory signal sequence which is posttranslationally cleaved. Searches of various DNA and protein databases revealed that IalA contains an N-terminal region of 35 amino acids with a high degree of homology to an NTPase consensus domain. There is 63.6% sequence conservation between the IalB protein and the invasion-associated protein Ail of Yersinia enterocolitica.

Amino Acid Sequence↗
PubMed1995

In vitro evaluation of the role of humoral immunity against Bartonella henselae.

The contribution of humoral immunity against Bartonella henselae was evaluated by examining the in vitro bactericidal activity of sera and the ability of these microorganisms to activate complement and stimulate phagocytosis and an oxidative burst in polymorphonuclear leukocytes. The organism was killed by complement-mediated cytolysis. Complement activation preferentially proceeded by the alternative pathway. The presence of specific antibodies did not increase the serum bactericidal activity or complement activation. However, phagocytosis and the subsequent production of oxygen radicals, evaluated by flow cytometry, were significantly enhanced in the presence of bacteria previously opsonized with immune sera.

Adult↗
PubMed1998

Murine model of Bartonella henselae infection in the immunocompetent host.

Bartonella henselae is an emerging pathogen causing cat scratch disease, bacillary angiomatosis, and peliosis hepatis. Progress in understanding the pathogenesis of and the immune response to these infections has been limited by the lack of an animal model. Following intraperitoneal infection of C57BL/6 mice with B. henselae, organs were cleared of cultivatable bacteria within 6 days. In contrast, B. henselae DNA could be detected in liver tissue for at least 3 months. Liver tissue showed granulomatous inflammation reaching its highest degree of intensity during the fourth week of infection and resolving within 12 weeks postinfection. This mouse model is applicable to the study of the pathogenesis of B. henselae and the immune response to this pathogen in the immunocompetent host.

AIDS-Related Opportunistic Infections↗
PubMed1998

Bartonella henselae invasion of feline erythrocytes in vitro.

Bartonella henselae, the causative agent of cat scratch disease, establishes long-term bacteremia in cats, in which it attaches to and invades feline erythrocytes (RBC). Feline RBC invasion was assessed in vitro, based on gentamicin selection for intracellular bacteria or by laser confocal microscopy and digital sectioning. Invasion rates ranged from 2 to 20% of the inoculum, corresponding to infection of less than 1% of the RBC. Invasion was a slow process, requiring >8 h before significant numbers of intracellular bacteria were detected. Pretreatment of the bacteria with trypsin, or of the RBC with trypsin or neuraminidase, had no effect, but pronase pretreatment of RBC resulted in a slight increase in invasion frequency. The ability to model B. henselae invasion of feline RBC in vitro should permit identification of bacterial surface components involved in this process and elucidate the significance of RBC invasion to transmission and infection in cats.

Animals↗
PubMed1999

Acute clinical disease in cats following infection with a pathogenic strain of Bartonella henselae (LSU16).

Bartonella henselae is the causative agent of human cat scratch disease as well as several serious sequelae of infections, including bacillary angiomatosis and bacillary peliosis. Conflicting reports describe the pathogenesis of B. henselae in the cat. In this study, we characterized a strain of B. henselae termed LSU16. This strain was isolated on rabbit blood agar from a naturally infected 10-month-old female cat during a recurrent episode of bacteremia. The bacterial species was confirmed by PCR-restriction fragment length polymorphism analysis. Nine cats were infected intradermally with 5 x 10(7) CFU of LSU16, and clinical signs, antibody responses, and bacteremia were monitored. All nine cats developed raised, erythematous areas at the site of inoculation within 72 h postinoculation; the swelling peaked at 14 days postinfection and was not palpable by 28 days postinfection. Fever developed in all nine cats between 6 and 16 days postinfection and lasted for 1 to 8 days. Between 6 and 16 days postinfection, all nine cats experienced lethargy which persisted 5 to 18 days. Seven of nine cats were bacteremic by day 7, and all nine cats had become bacteremic by 14 days postinfection. Bacteremia peaked at 14 to 28 days postinfection in all cats. In six of the nine infected cats, bacterial numbers reached nondetectable levels during the 7th week postinfection; however, a single animal maintained bacteremia to 18 weeks postinfection. All nine cats developed strong antibody responses to B. henselae, as determined by Western blot analysis and enzyme-linked immunosorbent assay. Subsequently, three naive cats were injected intradermally with blood from cats infected with LSU16 from a pure culture, and five naive cats were injected with feces from fleas which had been feeding on cats infected with a pure culture of LSU16. These cats developed signs similar to those described in the previous experiment and were euthanized at 5 weeks postinfection. We conclude that B. henselae LSU16 is a virulent strain of B. henselae in cats and propose that the virulence of B. henselae in cats is strain dependent.

Acute Disease↗
PubMed2000

Infection of human endothelial cells with Bartonella bacilliformis is dependent on Rho and results in activation of Rho.

Bartonella bacilliformis was continuously internalized into human endothelial cells beginning shortly after addition of the bacteria and continuing for at least 24 h after infection in vitro, with a major increase in uptake occurring between 16 and 24 h. Preincubation of endothelial cells with C3 exoenzyme, which inactivated intracellular Rho-GTPase, blocked internalization of the bacteria. Addition of C3 exoenzyme at any time after addition of the bacteria blocked further internalization of bacteria, including the major uptake of bacteria internalized at 16 to 24 h. Rho, a key signaling protein in pathways involving actin organization, was directly shown to be activated in endothelial cells undergoing infection with B. bacilliformis, with maximal activation and translocation to the plasma membrane at 12 to 16 h. At late times of infection, most of the bacteria were found in a perinuclear location. Staining of the Golgi complex with specific markers, anti-human Golgin-97, anti-KDEL receptor, and BODIPY-TR ceramide, showed colocalization of bacteria in the Golgi complex region. Disruption of the Golgi complex with brefeldin A scattered the bacteria from this perinuclear location and resulted in inhibition of internalization of the bacteria in endothelial cells.

ADP Ribose Transferases↗
PubMed2000

Transcriptional activation of the htrA (High-temperature requirement A) gene from Bartonella henselae.

Bacterial htrA genes are typically activated as part of the periplasmic stress response and are dependent on the extracytoplasmic sigma factor rpoE. A putative promoter region, P1, of the sigma(E)-type heat-inducible promoters has previously been identified upstream of the htrA gene of Bartonella henselae. Further analysis of the htrA mRNA by primer extension demonstrated that transcription initiates from P1 and a second region downstream of P1. This second promoter region, termed P2, had no sequence identity to sigma(E)-type heat-inducible promoters. Promoter regions were cloned individually and in tandem into pANT3 upstream of a promoterless version of the green fluorescent protein (GFP) gene (gfpmut3) and transformed into B. henselae by electroporation. The contiguous promoter region containing both P1 and P2 were necessary for the optimal transcriptional activation of the htrA gene. Promoter activity at 37 degrees C was distinctively higher than at 27 degrees C. However, thermal induction at 47 degrees C did not increase expression of gfpmut3. Invasion of human microvascular endothelial cells (HMEC-1) by B. henselae resulted in the formation of well-defined vacuoles containing clusters of bacteria exhibiting marked expression of gfpmut3 transcribed from the P1-P2 region. In addition, a moderate yet significant increase in the ratio of bacterial GFP to DNA was detected for intracellular bacteria compared to extracellular bacteria, indicating upregulation of htrA upon invasion of HMEC-1. The activation of specific genes in the intracellular environment may help us better understand the novel pathogenic mechanisms used by this bacterium.

Angiomatosis, Bacillary↗