Bartonella spp. as emerging human pathogens

Ocular bartonellosis

PURPOSE

To review recent advances in the basic and clinical biology of Bartonella-related eye disease.

METHOD

A review of the pertinent medical literature was performed.

RESULTS

A number of novel Bartonella species have been identified over the past decade. Of these, Bartonella henselae, the etiologic agent in cat scratch disease, is most often associated with ocular complications, which may include Parinaud oculoglandular syndrome, neuroretinitis, and focal retinochoroiditis. Although cat and flea exposure appear to be the main risk factors for contracting cat scratch disease, the diagnosis of ocular bartonellosis relies primarily on the recognition of suggestive clinical signs in conjunction with positive serologic testing. B. henselae-associated ocular complications are usually self-limited but may be treated with doxycycline or erythromycin, with or without rifampin, when the infections are severe or sight-threatening.

CONCLUSIONS

B. henselae infection is common and should be considered in patients with Parinaud oculoglandular syndrome, neuroretinitis, or focal retinochoroiditis, particularly when there is a history of cat or flea exposure.

Bartonella infection in animals: carriership, reservoir potential, pathogenicity, and zoonotic potential for human infection

Recent observations have begun to support a role for Bartonella spp. as animal as well as human pathogens. Bartonella spp. are vector-transmitted, blood-borne, intracellular, gram-negative bacteria that can induce prolonged infection in the host. Persistent infections in domestic and wild animals result in a substantial reservoir of Bartonella organisms in nature that can serve as a source for inadvertent human infection. The prevalence of bacteremia can range from 50 to 95% in selected rodent, cat, deer, and cattle populations. Dogs infected with Bartonella spp. can develop lameness, endocarditis, granulomatous lymphadenitis, and peliosis hepatis, lesions that have also been reported in association with human infection. Understanding the role of Bartonella spp. as pathogens in cats and other wild or domestic animals awaits the results of additional studies. Considering the extensive animal reservoirs and the large number of insects that have been implicated in the transmission of Bartonella spp., both animal and human exposure to these organisms may be more substantial than is currently believed.

Hemin-dependent growth and hemin binding of Bartonella henselae

Bartonella henselae causes cat-scratch disease and bacillary angiomatosis peliosis. The bacteria reside in erythrocytes of asymptomatic cats, which represent the natural reservoir for this pathogen. B. henselae is usually grown on blood-enriched media. Growth experiments on Brucella medium without blood demonstrated that heme compounds are essential for the growth of B. henselae and can completely substitute the addition of blood components. The heme precursor protoporphyrin IX alone, or in combination with FeCl(2) or FeCl(3), as well as transferrin or lactoferrin did not support growth, indicating that B. henselae cannot synthesize heme itself. Hemin supported growth even when free iron was chelated, indicating that hemin is also used as an iron source. Binding assays showed that hemin starvation increased the binding capacity of B. henselae for hemin, providing evidence that the bacteria carry a specific hemin uptake system, which might be regulated by hemin.

Isolation, sequencing and expression of Bartonella henselae omp43 and predicted membrane topology of the deduced protein

The infection of and interaction of human endothelial cells with Bartonella henselae is one of the most interesting aspects of Bartonella -associated disease. The gene encoding the 43 kDa B. henselae outer membrane protein (Omp43) that binds endothelial cells was cloned and sequenced. Sequence analysis revealed an open reading frame of 1206 nucleotides coding for a protein of 402 amino acids. Analysis of the deduced amino acid sequence shows 38% identity over the entire sequence to the Brucella spp. In addition to this Omp2b porin also shows a signal sequence and peptidase cleavage site. Cleavage of the signal peptide results in a mature 380 amino acid polypeptide with a predicted molecular weight of 42 kDa. Omp43 was expressed in Escherichia coli as a fusion protein. Purified recombinant Omp43 at concentrations of 11 and 2.75 microg/ml bound to intact human umbilical vein endothelial cells. Membrane topology analysis predicts that Omp43 exists as a 16 stranded beta barrel protein, similar to that predicted for the Omp2b Brucella abortus porin. Characterization and expression of the gene encoding Omp43 should provide a tool for further investigation of the role of adherence to endothelial cells in the pathogenesis of B. henselae.

Characterization of Bartonella clarridgeiae flagellin (FlaA) and detection of antiflagellin antibodies in patients with lymphadenopathy

Cat scratch disease (CSD) is a frequent clinical outcome of Bartonella henselae infection in humans. Recently, two case reports indicated Bartonella clarridgeiae as an additional causative agent of CSD. Both pathogens have been isolated from domestic cats, which are considered to be their natural reservoir. B. clarridgeiae and B. henselae can be distinguished phenotypically by the presence or absence of flagella, respectively. Separation of the protein content of purified flagella of B. clarridgeiae by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblot analysis indicated that the flagellar filament is mainly composed of a polypeptide with a mass of 41 kDa. N-terminal sequencing of 20 amino acids of this protein revealed a perfect match to the N-terminal sequence of flagellin (FlaA) as deduced from the sequence of the flaA gene cloned from B. clarridgeiae. The flagellin of B. clarridgeiae is closely related to flagellins of Bartonella bacilliformis and several Bartonella-related bacteria. Since flagellar proteins are often immunodominant antigens, we investigated whether antibodies specific for the FlaA protein of B. clarridgeiae are found in patients with CSD or lymphadenopathy. Immunoblotting with 724 sera of patients suffering from lymphadenopathy and 100 healthy controls indicated specific FlaA antibodies in 3.9% of the patients' sera but in none of the controls. B. clarridgeiae FlaA is thus antigenic and expressed in vivo, providing a valuable tool for serological testing. Our results further indicate that B. clarridgeiae might be a possible etiologic agent of CSD or lymphadenopathy. However, it remains to be clarified whether antibodies to the FlaA protein of B. clarridgeiae are a useful indicator of acute infection.

Bartonella infection in animals: carriership, reservoir potential, pathogenicity, and zoonotic potential for human infection

Recent observations have begun to support a role for Bartonella spp. as animal as well as human pathogens. Bartonella spp. are vector-transmitted, blood-borne, intracellular, gram-negative bacteria that can induce prolonged infection in the host. Persistent infections in domestic and wild animals result in a substantial reservoir of Bartonella organisms in nature that can serve as a source for inadvertent human infection. The prevalence of bacteremia can range from 50 to 95% in selected rodent, cat, deer, and cattle populations. Dogs infected with Bartonella spp. can develop lameness, endocarditis, granulomatous lymphadenitis, and peliosis hepatis, lesions that have also been reported in association with human infection. Understanding the role of Bartonella spp. as pathogens in cats and other wild or domestic animals awaits the results of additional studies. Considering the extensive animal reservoirs and the large number of insects that have been implicated in the transmission of Bartonella spp., both animal and human exposure to these organisms may be more substantial than is currently believed.

Rickettsia prowazekii and Bartonella henselae: differences in the intracellular life styles revisited

Within the alpha subdivision of proteobacteria, the arthropod-borne human pathogens Rickettsia prowazekii and Bartonella henselae provide examples of bacteria with obligate and facultative intracellular life styles, respectively. The complete genome sequence of R. prowazekii has been published, whereas the sequencing of the B. henselae genome is in its final stage. Here, we provide a brief overview of a comparative analysis of both genomes based on the delineated metabolic properties. The relative proportion of genes devoted to basic information processes is similar in the two genomes. In contrast, a full set of genes encoding proteins involved in the biosynthesis of amino acids and nucleotides is present in B. henselae, while the majority of these genes is absent from R. prowazekii. This suggests that B. henselae has a better potential for growth in the free-living mode, whereas R. prowazekii is more specialised to growth in an intracellular environment. Functional genomics will provide the potential to further resolve the genetic basis for successful human infections by these important parasites.

Bartonella henselae infection as a cause of fever of unknown origin

Fourteen of 41 patients (34%) with a serological diagnosis of Bartonella henselae infection were found to have prolonged fever or fever of unknown origin, suggesting that generalized systemic B. henselae infection is not rare in immunocompetent healthy individuals.

Recent Advances in Diagnosis and Treatment of Cat Scratch Disease

The cause of cat scratch disease (CSD), first described in France in 1950 and in the United States in 1951, was unknown until 1983 when the bacterium in lymph nodes was detected using a Warthin-Starry silver stain. Afipia felis has been an infrequent cause of CSD since1988, when this gram-negative bacterium was first isolated from 10 patients with CSD. In 1992 Bartonella organisms were isolated from immunocompetent and immunocompromised patients. An indirect fluorescent antibody test to detect bartonella-specific serum immunoglobulins was developed in 1992. Since then multiple studies have shown that three Bartonella species may produce either CSD in humans, usually Bartonella henselae or Bartonella clarridgeiae, or bacteremia in healthy cats. Also, these two bacteria and Bartonella quintana cause bacillary angiomatosis, bacillary peliosis, or relapsing bacteremia in humans. Cats are healthy carriers of Bartonella organisms and may be bacteremic for months to years. Cat-to-cat transmission of Bartonella organisms involves the cat flea in absence of direct contact transmission. CSD is the most common cause of regional lymphadenitis in children and adolescents. Present knowledge on the etiology, clinical features, epidemiology, pathogenesis, diagnosis, and management of CSD are presented. Also, brief comments about the etiology, clinical presentation, and treatment of bacillary angiomatosis and bacillary peliosis are provided.

Bartonellosis. New and old

The number of species that comprise the family of Bartonellaceae, genus Bartonella, has recently increased from one to 11 species, five of which have been associated with different diseases and syndromes in humans. The rapidly growing number of human pathogens has led several investigators to regard bartonellosis and other associated syndromes as important emerging infectious diseases. This article presents the history and epidemiology, clinical features, diagnosis, and treatment of bartonellosis and associated diseases, including Carrión's disease, trench fever, endocarditis and bacteremia, bacillary angiomatosis, and cat-scratch disease.

Cloning, sequencing, and expression of three Bartonella henselae genes homologous to the Agrobacterium tumefaciens VirB region

A 17-kDa, immunodominant antigen of Bartonella henselae Houston-1 has previously been cloned, sequenced, and characterized. This clone (H13) contains the 17-kDa antigen gene plus a partial open reading frame, designated ORF1, which is 459 nucleotides long and is directly upstream of the 17-kDa gene. Comparison of the deduced partial amino acid sequence of ORF1 with that of other known genes in GenBank revealed significant identity with several other bacterial virulence genes, including VirB4 of the Agrobacterium tumefaciens virB operon (56/149 amino acids). An overlapping clone, pGB3, was recovered and shown to contain a 3.0-kb region upstream of the 17-kDa gene. Sequence analysis revealed three ORFs upstream of the gene. The deduced amino acid sequence of each ORF was compared with sequences in GenBank, and identity was found with VirB2, VirB3, and VirB4 of A. tumefaciens. In vitro transcription/translation and SDS-PAGE demonstrated that three proteins of 9 kDa, 10 kDa, and 92 kDa, corresponding to the predicted molecular weight of 10.9 kDa, 11.7 kDa, and 89.9 kDa of VirB2, VirB3, and VirB4, respectively, could be expressed from these coding regions. These results indicate that virulence-associated genes and their overall chromosomal arrangement are relatively well conserved between B. henselae and other gram-negative bacteria such as A. tumefaciens.

Conservation of the 17-kilodalton antigen gene within the genus Bartonella

The 17-kDa antigen of Bartonella henselae has previously been shown to elicit a strong humoral immune response in patients with cat scratch disease (CSD) and to be useful in screening human serum samples for CSD. In this study, PCR amplification of genes homologous to the 17-kDa antigen gene of B. henselae was performed using genomic DNAs from several species of Bartonella, including the currently recognized human pathogens. Amplicons of similar size were demonstrated using the following chromosomal DNA templates: B. henselae (two strains), B. quintana (two strains), B. elizabethae, B. clarridgeiae, B. vinsonii subsp. vinsonii, and B. vinsonii subsp. berkhoffii. No evidence of a B. bacilliformis homolog of the 17-kDa antigen gene was obtained using multiple primer pairs. DNA sequencing revealed open reading frames capable of coding for proteins with sizes similar to that of the 17-kDa antigen of B. henselae in all of the amplicons; however, extensive sequence divergence across the genus was noted. Cloning of the amplified products into pUC19 resulted in recombinants that directed synthesis of homologs of the 17-kDa protein. Immunoblot analysis using human sera from CSD cases demonstrated very little cross-reactivity among different species for this protein. In contrast, immunoblots using rabbit serum raised to the recombinant B. henselae antigen showed extensive cross-reactivity with the proteins of other Bartonella species. The data suggest that the use of the 17-kDa antigen as a serologic reagent may allow the development of more specific diagnostic assays. Furthermore, the nucleotide sequences from the various versions of the 17-kDa antigen gene should be useful for rapid identification of Bartonella at the species level.

Sequence variation in the ftsZ gene of Bartonella henselae isolates and clinical samples

In a search for methods for subtyping of Bartonella henselae in clinical samples, we amplified and sequenced a 701-bp region in the 3' end of the ftsZ gene in 15 B. henselae isolates derived from cats and humans in the United States and Europe. The ftsZ sequence variants that were discovered were designated variants Bh ftsZ 1, 2, and 3 and were compared with 16S rRNA genotypes I and II of the same isolates. There was no ftsZ gene variation in the strains of 16S rRNA type I, all of which were Bh ftsZ 1. The type II strains constituted two groups, with nucleotide sequence variation in the ftsZ gene resulting in amino acid substitutions at three positions, one of which was shared by the two groups. One 16S rRNA type II isolate had an ftsZ gene sequence identical to those of the type I strains. Variants Bh ftsZ 1 and 2 were detected in tissue specimens from seven Swedish patients with diagnoses such as chronic multifocal osteomyelitis, cardiomyopathy, and lymphadenopathy. Patients with similar clinical entities displayed either Bh ftsZ variant. The etiological role of B. henselae in these patients was supported by positive Bartonella antibody titers and/or amplification and sequencing of a part of the B. henselae gltA gene. B. henselae ftsZ gene sequence variation may be useful in providing knowledge about the epidemiology of various B. henselae strains in clinical samples, especially when isolation attempts have failed. This report also describes manifestations of atypical Bartonella infections in Sweden.

Unusual eruption as a presenting symptom of cat scratch disease

Cat scratch disease (CSD) is a common infectious cause of subacute regional lymphadenopathy. Bartonella henselae is the principal etiologic agent. About 10% of CSD patients experience atypical manifestations, including rashes. The most common cutaneous manifestation of CSD is a papule at the inoculation site. We report a case of CSD presenting with an eruption on the upper trunk, reminiscent of Sweet's syndrome, accompanied by lymphadenopathy, arthralgia, and fever. Response to systemic corticosteroids was remarkable. Histopathologic findings refuted the diagnosis of Sweet's syndrome. Identification of anti-B henselae antibodies and B henselae DNA in the affected lymph node confirmed the diagnosis of CSD. This is a first report of extensive papuloedematous eruption as a cutaneous manifestation of CSD. Accurate diagnosis is possible due to the availability of serological tests and DNA amplification techniques.

Molecular analysis of riboflavin synthesis genes in Bartonella henselae and use of the ribC gene for differentiation of Bartonella species by PCR

The biosynthesis pathway for riboflavin (vitamin B(2)), the precursor of the essential cofactors flavin mononucleotide and flavin adenine dinucleotide, is present in bacteria and plants but is absent in vertebrates. Due to their conservation in bacterial species and their absence in humans, the riboflavin synthesis genes should be well suited either for detection of bacterial DNA in human specimens or for the differentiation of pathogenic bacteria by molecular techniques. A DNA fragment carrying the genes ribD, ribC, and ribE, which encode homologues of riboflavin deaminase (RibD) and subunits of riboflavin synthetase (RibC and RibE), respectively, was isolated from a plasmid-based DNA library of the human pathogen Bartonella henselae by complementation of a ribC mutation in Escherichia coli. Sequence analysis of the ribC gene region in strains of B. henselae, which were previously shown to be genetically different, revealed that the ribC gene is highly conserved at the species level. PCR amplification with primers derived from the ribC locus of B. henselae was used to isolate the corresponding DNA regions in B. bacilliformis, B. clarridgeiae, and B. quintana. Sequence analysis indicated that the riboflavin synthesis genes are conserved and show the same operon-like genetic organization in all four Bartonella species. Primer oligonucleotides designed on the basis of localized differences within the ribC DNA region were successfully used to develop species-specific PCR assays for the differentiation of B. henselae, B. clarridgeiae, B. quintana, and B. bacilliformis. The results obtained indicate that the riboflavin synthesis genes are excellent targets for PCR-directed differentiation of these emerging pathogens. The PCR assays developed should increase our diagnostic potential to differentiate Bartonella species, especially B. henselae and the newly recognized species B. clarridgeiae.

Semiquantitative species-specific detection of Bartonella henselae and Bartonella quintana by PCR-enzyme immunoassay

Bartonella henselae is the main causative agent of cat-scratch disease, and both B. henselae and Bartonella quintana cause angioproliferative disorders such as bacillary angiomatosis. To increase the sensitivity of Bartonella detection by PCR and to improve the species differentiation, we developed a semiquantitative, species-specific PCR-based enzyme immunoassay (EIA). The 16S rRNA gene was selected as the target sequence. Internal nucleotide sequences derived from the amplified 16S rRNA region were used to develop species-specific oligonucleotide probes for B. henselae and B. quintana. Biotin-labeled PCR products were immobilized on streptavidin-coated microtiter plates, hybridized to a digoxigenin-labeled probe, and detected with antidigoxigenin peroxidase conjugate. No cross-hybridization with other Bartonella or non-Bartonella species was observed. This EIA was as sensitive as dot blot hybridization and was 10 times more sensitive than visualization of PCR products on agarose gels. Serial dilutions of B. henselae and B. quintana suspensions demonstrated that an optical density (OD) of approximately 0.200 was equivalent to 5 CFU in the reaction mixture. By comparing the OD of the bacterial dilutions with that obtained from clinical specimens we could determine that the number of CFU in clinical samples ranged from 10(3) to 10(6) CFU/ml. The PCR-EIA developed in the present study is a rapid, sensitive, and simple method for the diagnosis of B. henselae and B. quintana infections.

Development of a system for genetic manipulation of Bartonella bacilliformis

Lack of a system for site-specific genetic manipulation has severely hindered studies on the molecular biology of all Bartonella species. We report the first site-specific mutagenesis and complementation for a Bartonella species. A highly transformable strain of B. bacilliformis, termed JB584, was isolated and found to exhibit a significant increase in transformation efficiency with the broad-host-range plasmid pBBR1MCS-2, relative to wild-type strains. Restriction analyses of genomic preparations with the methylation-sensitive restriction enzymes ClaI and StuI suggest that strain JB584 possesses a dcm methylase mutation that contributes to its enhanced transformability. A suicide plasmid, pUB1, which contains a polylinker, a pMB1 replicon, and a nptI kanamycin resistance cassette, was constructed. An internal 508-bp fragment of the B. bacilliformis flagellin gene (fla) was cloned into pUB1 to generate pUB508, a fla-targeting suicide vector. Introduction of pUB508 into JB584 by electroporation generated eight Kan(r) clones of B. bacilliformis. Characterization of one of these strains, termed JB585, indicated that allelic exchange between pUB508 and fla had occurred. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoblotting, and electron microscopy showed that synthesis of flagellin encoded by fla and secretion/assembly of flagella were abolished. Complementation of fla in trans was accomplished with a pBBR1MCS recombinant containing the entire wild-type fla gene (pBBRFLAG). These data conclusively show that inactivation of fla results in a bald, nonmotile phenotype and that pMB1 and REP replicons make suitable B. bacilliformis suicide and shuttle vectors, respectively. When used in conjunction with the highly transformable strain JB584, this system for site-specific genetic manipulation and complementation provides a new venue for studying the molecular biology of B. bacilliformis.

Culture of Bartonella quintana and Bartonella henselae from human samples: a 5-year experience (1993 to 1998)

Bartonella quintana and Bartonella henselae are fastidious gram-negative bacteria responsible for bacillary angiomatosis, trench fever, cat scratch disease, and endocarditis. During a 5-year period, we received 2,043 samples for culture of Bartonella sp. We found Bartonella sp. to be the etiologic agent in 38 cases of endocarditis, 78 cases of cat scratch disease, 16 cases of bacteremia in homeless people, and 7 cases of bacillary angiomatosis. We correlated the results of positive cultures with the clinical form of the disease, type of sample, culture procedure, PCR-based genomic detection, and antibody determination. Seventy-two isolates of B. quintana and nine isolates of B. henselae from 43 patients were obtained. Sixty-three of the B. quintana isolates and two of the B. henselae isolates, obtained from patients with no prior antibiotic therapy, were stably subcultured. The sensitivity of culture was low when compared with that of PCR-based detection methods in valves of patients with endocarditis (44 and 81%, respectively), skin biopsy samples of patients with bacillary angiomatosis (43 and 100%, respectively), and lymph nodes of cat scratch disease (13 and 30%, respectively). Serological diagnosis was also more sensitive in cases of endocarditis (97%) and cat scratch disease (90%). Among endocarditis patients, the sensitivity of the shell vial culture assay was 28% when inoculated with blood samples and 44% when inoculated with valvular biopsy samples, and the sensitivity of both was significantly higher than that of culture on agar (5% for blood [P = 0.045] and 4% for valve biopsy samples [P < 0.0005]). The most efficient culture procedure was the subculture of blood culture broth into shell vials (sensitivity, 71%). For patients with endocarditis, previous antibiotic therapy significantly affected results of blood culture; no patient who had been administered antibiotics yielded a positive blood culture, whereas 80% of patients with no previous antibiotic therapy yielded positive blood cultures (P = 0.0006). Previous antibiotic therapy did not, however, prevent isolation of Bartonella sp. from cardiac valves but did prevent the establishment of strains, as none of the 15 isolates from treated patients could be successfully subcultured. For the diagnosis of B. quintana bacteremia in homeless people, the efficiency of systematic subculture of blood culture broth onto agar was higher than that of direct blood plating (respective sensitivities, 98 and 10% [P < 10(-7)]). Nevertheless, both procedures are complementary, since when used together their sensitivity reached 100%. All homeless people with positive blood cultures had negative serology. The isolation rate of B. henselae from PCR-positive lymph nodes, in patients with cat scratch disease, was significantly lower than that from valves of endocarditis patients and skin biopsy samples from bacillary angiomatosis patients (13 and 33%, respectively [P = 0.084]). In cases of bacillary angiomatosis for which an agent was identified to species level, the isolation rate of B. henselae was lower than the isolation rate of B. quintana (28 and 64%, respectively [P = 0.003]). If culture is to be considered an efficient tool for the diagnosis of several Bartonella-related diseases, methodologies need to be improved, notably for the recovery of B. henselae from lymph nodes of patients with cat scratch disease.

Characterization of Bartonella henselae-specific immunity in BALB/c mice

BALB/c mice were inoculated with Bartonella henselae by both systemic and mucosal routes. Culture analysis of tissues from mice infected intraperitoneally with a high dose of B. henselae yielded positive results 24 hr after infection. However, culture analysis of blood taken between 6 hr and 7 days after infection from groups receiving live B. henselae were negative. Following intraperitoneal infection, B. henselae was detected by polymerase chain reaction in liver and mesenteric lymph nodes by 6 hr and up to 7 days after infection in liver, kidney and spleen tissue. Enzyme-linked immunosorbent assay (ELISA) of serum samples collected as early as 13 days after infection indicated humoral immune responses to B. henselae. Specific humoral responses remained through week 6. Analysis of faecal samples revealed induction of B. henselae-specific immunoglobulin A by day 28 after infection. In addition, B. henselae-specific cellular responses were indicated by a positive delayed-type hypersensitivity and a T helper 1 (Th1) (CD4+ T cell)-type cytokine response following in vitro stimulation of splenocytes. The significance and implications of these data in relation to B. henselae infections are discussed.

Clinical and pathologic evaluation of chronic Bartonella henselae or Bartonella clarridgeiae infection in cats

Human Bartonella infections result in diverse medical presentations, whereas many cats appear to tolerate chronic bacteremia without obvious clinical abnormalities. Eighteen specific-pathogen-free cats were inoculated with Bartonella henselae- and/or Bartonella clarridgeiae-infected cat blood and monitored for 454 days. Relapsing bacteremia did not correlate with changes in protein profiles or differences in antigenic protein recognition. Intradermal skin testing did not induce a delayed type hypersensitivity reaction to cat scratch disease skin test antigen. Thirteen cats were euthanatized at the end of the study. Despite persistent infection, clinical signs were minimal and gross necropsy results were unremarkable. Histopathology revealed peripheral lymph node hyperplasia (in all of the 13 cats), splenic follicular hyperplasia (in 9 cats), lymphocytic cholangitis/pericholangitis (in 9 cats), lymphocytic hepatitis (in 6 cats), lymphoplasmacytic myocarditis (in 8 cats), and interstitial lymphocytic nephritis (in 4 cats). Structures suggestive of Bartonella were visualized in some Warthin-Starry stained sections, and Bartonella DNA was amplified from the lymph node (from 6 of the 13 cats), liver (from 11 cats) heart (from 8 cats), kidney (from 9 cats), lung (from 2 cats), and brain (from 9 cats). This study indicates that B. henselae or B. clarridgeiae can induce chronic infection following blood transfusion in specific-pathogen-free cats and that Bartonella DNA can be detected in blood, brain, lymph node, myocardium, liver, and kidney tissues of both blood culture-positive cats and blood culture-negative cats. Detection of histologic changes in these cats supports a potential etiologic role for Bartonella species in several idiopathic disease processes in cats.

Cat scratch disease diagnosed by polymerase chain reaction in a patient with suspected tuberculous lymphadenitis

We present a patient diagnosed as having tuberculous lymphadenitis after lymph node biopsy and referred for tuberculous therapy. On review, because of recent cat exposure, she was tested for cat scratch disease (CSD), but serological tests for Bartonella henselae were negative. However, the diagnosis of CSD was confirmed, and tuberculosis excluded, by polymerase chain reaction techniques. This case serves as a reminder that CSD may mimic tuberculosis histologically and that sensitive molecular diagnostic tests are available.

Seroepidemiology of Bartonella vinsonii subsp. berkhoffii infection in California coyotes, 1994-1998

The prevalence of antibodies to Bartonella vinsonii subsp. berkhoffii in coyotes (Canis latrans) in California ranged from 51% in central to 34% in southern and 7% in northern California. Seropositive coyotes were more likely to be from coastal than inland counties (p clustered distribution of Bartonella seropositivity in coyotes suggests that B. vinsonii subsp. berkhoffii infection is vectorborne. Further investigation is warranted to evaluate which arthropods are vectors and what the mode of transmission is from wildlife to domestic dogs and possibly humans.

Characterization of human immunoglobulin (Ig) isotype and IgG subclass response to Bartonella henselae infection

Serologic parameters of cat scratch disease (CSD) were evaluated by Western blot analysis. Sera from patients with serologically confirmed CSD antigen were screened for immunoglobulin (Ig) isotype-specific as well as IgG subclass-specific reactivity against Bartonella henselae whole-cell antigen. Bartonella-negative control sera were used to determine baseline antibody activity. Heterogeneous B. henselae-specific IgG reactivity with numerous protein bands, ranging from >150 to <17 kDa, was observed. Though individual banding patterns were variable, one approximately 83-kDa B. henselae protein (Bh83) was immunoreactive with all CSD sera tested, suggesting it is a conserved antigen during infection. Bh83 was not recognized by reference human antisera against Rickettsia rickettsii, Chlamydia group positive, Treponema pallidum, Orientia tsutsugamushi, Fransciscella tularensis, Ehrlichia chaffeensis, Mycoplasma pneumoniae, and Escherichia coli, although other cross-reactive proteins were evident. Significantly, CSD sera failed to recognize the 83-kDa protein when tested against Bartonella quintana antigen, though sera from B. quintana-infected patients did react to Bh83. This cross-reactivity suggests epitope conservation during infection with B. henselae or B. quintana. Western blot analysis further revealed similar banding patterns when B. henselae was reacted against the Ig isotypes IgG and IgG1 and both secretory and alpha chains of IgA. Neither IgM nor IgE reacted significantly to Bartonella antigen by our Western blot analysis. Dissection of the antibody response at the IgG subclass level indicated that prominent antigen recognition was limited to IgG1. These observations provide insight into induced immunity during CSD and provide evidence for conserved epitope expression during infection with B. henselae or B. quintana.

Two different genotypes of Bartonella henselae in children with cat-scratch disease and their pet cats

Two genotypes (I and II) of Bartonella henselae are involved in cat-scratch disease (CSD). Lymph node biopsies were taken from 3 children suffering from CSD, and blood cultures were obtained from their pet cats. Cat-scratch disease was confirmed serologically, histologically and by detection of B. henselae DNA in all 3 lymph nodes by PCR. Bartonella henselae grew in all cats' blood cultures. The first 2 children were siblings. Both children and their pet cats were infected with B. henselae genotype II, and the third patient and her cat were infected with B. henselae genotype I. In all cases, there were no essential differences in the clinical manifestations of the infection caused by these 2 genotypes of B. henselae.

Comparison of different DNA fingerprinting techniques for molecular typing of Bartonella henselae isolates

Seventeen isolates of Bartonella henselae from the region of Freiburg, Germany, obtained from blood cultures of domestic cats, were examined for their genetic heterogeneity. On the basis of different DNA fingerprinting methods, including pulsed-field gel electrophoresis (PFGE), enterobacterial repetitive intergenic consensus (ERIC)-PCR, repetitive extragenic palindromic (REP) PCR, and arbitrarily primed (AP)-PCR, three different variants were identified among the isolates (variants I to III). Variant I included 6 strains, variant II included 10 strains, and variant III included only one strain. By all methods used, the isolates could be clearly distinguished from the type strain, Houston-1, which was designated variant IV. A previously published type-specific amplification of 16S rDNA differentiated two types of the B. henselae isolates (16S rRNA types 1 and 2). The majority of the isolates (16 of 17), including all variants I and II, were 16S rRNA type 2. Only one isolate (variant III) and the Houston-1 strain (variant IV) comprised the 16S rRNA type 1. Comparison of the 16S rDNA sequences from one representative strain from each of the three variants (I to III) confirmed the results obtained by 16S rRNA type-specific PCR. The sequences from variant I and variant II were identical, whereas the sequence of variant III differed in three positions. All methods applied in this study allowed subtyping of the isolates. PFGE and ERIC-PCR provided the highest discriminatory potential for subtyping B. henselae strains, whereas AP-PCR with the M13 primer showed a very clear differentiation between the four variants. Our results suggest that the genetic heterogeneity of B. henselae strains is high. The methods applied were found useful for typing B. henselae isolates, providing tools for epidemiological and clinical follow-up studies.

Bacillary angiomatosis in immunocompromised patients

OBJECTIVES

To report seven cases of bacillary angiomatosis; to evaluate the most useful diagnostic tools; to analyse the clinical and epidemiological features associated with Bartonella quintana or Bartonella henselae infections.

DESIGN

Clinical, diagnostic and epidemiological evaluation of 37 speciated bacillary angiomatosis cases in the literature, including the seven patients in our study.

METHODS

Pathological examination of tissue samples, including Warthin-Starry staining and immunohistology; titre of antibodies to Bartonella sp.; detection of Bartonella sp. in blood and biopsy materials by culture or PCR; and statistical analysis of clinical and epidemiological features associated with B. quintana or B. henselae bacillary angiomatosis cases.

RESULTS

Seven immunocompromised patients (six with AIDS and one patient with acute leukaemia) had bacillary angiomatosis confirmed by histology. B. quintana was cultured in three patients, whereas B. henselae DNA was amplified by PCR in the remaining four patients. Serum from only one patient reacted with Bartonella antigens. Amongst the 14 B. quintana and 23 B. henselae bacillary angiomatosis cases now reported in the literature, lymphadenopathies were significantly more frequent in B. henselae-infected patients, and neurological disorders of the central nervous system in B. quintana-infected patients. Risk factors were contact with cats, and homelessness or poor socioeconomic status in B. henselae and B. quintana bacillary angiomatosis cases, respectively.

CONCLUSIONS

Although diagnosis of bacillary angiomatosis often remains solely based upon histology, culture or PCR-based methods are useful for the detection of Bartonella sp., and allow identification of the species involved, which is necessary to further characterize clinical and epidemiological features associated with B. quintana or B. henselae infections.

Construction of versatile high-level expression vectors for Bartonella henselae and the use of green fluorescent protein as a new expression marker

Expression vectors suitable for directing high levels of protein synthesis in Bartonella henselae have been constructed based on the mobilisable broad-host-range (IncQ) plasmidpMMB206. They confer kanamycin resistance and feature the taclac (tac-lacUV5 in tandem) promoters in front of a polylinker followed by the rrnB transcriptional stop point. While expression of genes fused to the taclac promoter is constitutive in one vector, the lacIq gene carried by the other vector allows a controlled, IPTG-inducible gene expression. These vectors were tested by subcloning a mutated gfp gene coding for the green fluorescent protein (GFP) from Aequorea victoria into the multiple cloning site and introducing the resulting plasmids into Escherichia coli and B. henselae. GFP expression was determined by measuring fluorescence via flow cytometry or directly by immunoblotting. Compared to E. coli, expression of GFP in B. henselae was more tightly controlled by lacIq and resulted in much higher levels of both IPTG-induced and constitutive gene expression. In vitro infection of endothelial cells indicated that GFP expression does not adversely affect the interaction of B. henselae with host cells. These data demonstrate that (i) the established expression vectors are useful for directing controlled or constitutive high-level protein synthesis in B. henselae and (ii) that GFP is a valuable expression marker which may has important applications in studying the bacterial genetics and cellular interactions of this emerging human pathogen.

Prospective randomized double blind placebo-controlled evaluation of azithromycin for treatment of cat-scratch disease

OBJECTIVE

To determine the efficacy of azithromycin in the treatment of patients with typical cat-scratch disease.

DESIGN

Prospective, randomized, double blind, placebo-controlled clinical trial.

SETTING

Large military medical center and its referring clinics.

PATIENTS

Active duty military members and their dependents with laboratory-confirmed, clinically typical cat-scratch disease.

INTERVENTION

Study participants assigned by randomization to treatment with oral azithromycin or placebo for 5 days.

OUTCOME MEASURES

Lymph node volume was calculated using three dimensional ultrasonography at entry and at weekly intervals. The ultrasonographer was blinded to the treatment groups. Endpoint evaluations were predetermined as time in days to 80% resolution of the initial total lymph node volume.

RESULTS

Demographic and clinical data showed that the azithromycin and placebo treatment groups were comparable at entry although the placebo group tended to be older. Eighty percent decrease of initial lymph node volume was documented in 7 of 14 azithromycin-treated patients compared with 1 of 15 placebo-treated controls during the first 30 days of observation (P = 0.026). After 30 days there was no significant difference in rate or degree of resolution between the two groups.

CONCLUSIONS

Treatment of patients with typical cat-scratch disease with oral azithromycin for five days affords significant clinical benefit as measured by total decrease in lymph node volume within the first month of treatment.

Persistent infection of pets within a household with three Bartonella species

We monitored by blood culture and immunofluorescence assay (IFA) bartonella infection in one dog and eight cats in a household to determine the prevalence and persistence of the infection as well as its transmissibility to humans. Ectoparasite control was rigorously exercised. During a 3-year period, Bartonella clarridgeiae was recovered from one cat on two occasions, and B. henselae was isolated from another cat on four occasions. During a 16-month period, B. vinsonii subsp. berkhoffii was isolated from the dog on 8 of 10 culture attempts. Despite extensive household contact, the pet owner was seronegative to all three species by IFA for Bartonella-specific immunoglobulin G.

Efficacy of enrofloxacin or doxycycline for treatment of Bartonella henselae or Bartonella clarridgeiae infection in cats

Enrofloxacin and doxycycline are antimicrobial agents used to treat bacterial diseases of cats. In vitro susceptibility data indicate that either drug should be effective against Bartonella species. In vivo efficacies of these drugs for eradication of chronic Bartonella henselae or Bartonella clarridgeiae infections were examined in 18 experimentally infected cats and 25 naturally exposed cats treated with enrofloxacin (22.7 mg given orally [PO] every 12 h [q12h] [14 days, n = 10; 28 days, n = 13]) or with doxycycline (25 mg PO q12h [14 days, n = 9; 28 days, n = 8]) or not treated (n = 3). Plasma drug concentrations were determined in experimental cats by high-performance liquid chromatography. Only 23 of 43 cats enrolled ultimately met inclusion criteria. Bacteremia was eliminated for 12 to 25 weeks posttreatment in four of seven cats receiving 14 days of enrofloxacin, five of seven cats receiving 28 days of enrofloxacin, one of six cats receiving 14 days of doxycycline, and one of two cats receiving 28 days of doxycycline. Defining a negative result by blood culture as treatment success may be erroneous; these results may reflect the insensitivity of blood culture or the relapsing nature of Bartonella bacteremia. Our results suggest that MICs obtained with axenic media do not predict antimicrobial activity against intracellular Bartonella, that a long treatment course is required to eliminate infection, and that duration of therapy correlates with pretreatment bacterial load. Given current concern about the development of antimicrobial resistance, we would reserve recommendation for treatment to cats owned by an immunocompromised individual or as an alternative to euthanasia of a pet.

Evaluation of commercial slides for detection of immunoglobulin G against Bartonella henselae by indirect immunofluorescence

Four commercial slides were compared with in-house slides for the detection of immunoglobulin G (IgG) against Bartonella henselae in 58 healthy persons from a rural region by an indirect immunofluorescence assay. MRL-BA slides (MRL Diagnostics, USA) and Virion slides (Virion, Switzerland) with agar-derived Bartonella henselae showed IgG titers of > or = 1:256 in 44.8% and 51.7%, respectively, whereas Bion slides (Bios, Germany), MRL-Vero slides (MRL Diagnostics), and in-house slides with cell-associated Bartonella henselae showed such titers in 3.4%, 5.1% and 3.4%, respectively. The MRL-Vero slides (Bartonella IgG substrate slides, MRL Diagnostics) were further evaluated with 26 patients with cat scratch disease, 20 patients with lymphadenopathy not due to cat scratch disease, 100 blood donors from an urban area, and 120 blood donors from a mixed urban/rural area. In our mixed urban/rural population the IgG titer of 1:256 had a sensitivity of 84.6% and a specificity of 93.4% for the serodiagnosis of cat scratch disease. Seroprevalence was higher in blood donors from the mixed area (50.8%) than from the urban area (37%). MRL-Vero slides were considered useful for the serodiagnosis of cat scratch disease by indirect immunofluorescence and have replaced our in-house system. However, patients with low IgG titers should be retested three to four weeks after initial sampling to demonstrate a possible rise of IgG titers in paired sera.