A chemically defined liquid medium that supports primary isolation of Rochalimaea (Bartonella) henselae from blood and tissue specimens

Blood Supplementation Enhances Bartonella henselae Growth and Molecular Detection of Bacterial DNA in Liquid Culture

Bacteria of the genus Bartonella, a member of the Alphaproteobacteria, are fastidious, Gram-negative, aerobic bacilli that comprise numerous species, subspecies, and genotypes. Bartonella henselae, with a worldwide distribution, infects cats, dogs, horses, humans, and other mammals. Diagnostically, direct detection of Bartonella henselae in patient blood specimens by culture or molecular methods is required to confirm infection with this bacterium. Enrichment blood culture combined with quantitative PCR (qPCR) or ddPCR enhances the sensitivity of direct detection. The addition of sheep blood to liquid culture media increased the Bartonella henselae DNA concentration compared to controls, additionally improving PCR direct detection sensitivity. IMPORTANCE This study aims to improve diagnostic detection of Bartonella henselae. Patient samples are combined with enriched bacterial cultures aimed at growing Bartonella henselae for the best possible chance at detection. However, current Bartonella growth methods could be improved. The DNA extraction method used by most laboratories should also be optimized. Sheep blood was added to increase the growth of Bartonella henselae and multiple DNA extraction methods were to be compared to each other.

Guidelines for the Isolation, Molecular Detection, and Characterization of Bartonella Species

Bartonellae are fastidious, facultative, intracellular vector-borne bacteria distributed among mammalian reservoirs worldwide. The pathogenic potential of many Bartonella spp. has increased the interest in these bacteria and advanced their research. Isolation of Bartonella spp. is laborious using classical bacteriological methods and requires specific conditions and prolonged incubation periods. In contrast, molecular methods for detection of Bartonella DNA are considered as more practical and sensitive than the former. Among the molecular methods, the use of real-time PCR assays for primary screening of Bartonella spp., followed by several molecular confirmatory assays, using either conventional or real-time PCR, is recommended. Although primary isolation of Bartonella is a laborious task, we encourage its application to all PCR-positive samples as this is the most reliable proof for the presence of live bacteria. Moreover, a successful trial will enable a broader molecular characterization and speciation of isolated colonies. The present guideline gathers and summarizes recommendations, including advantages and limitations of isolation and molecular detection of Bartonella from mammalian and arthropod samples.

Persistence of Bartonella spp. stealth pathogens: from subclinical infections to vasoproliferative tumor formation

Bartonella spp. are facultative intracellular bacteria that typically cause a long-lasting intraerythrocytic bacteremia in their mammalian reservoir hosts, thereby favoring transmission by blood-sucking arthropods. In most cases, natural reservoir host infections are subclinical and the relapsing intraerythrocytic bacteremia may last weeks, months, or even years. In this review, we will follow the infection cycle of Bartonella spp. in a reservoir host, which typically starts with an intradermal inoculation of bacteria that are superficially scratched into the skin from arthropod feces and terminates with the pathogen exit by the blood-sucking arthropod. The current knowledge of bacterial countermeasures against mammalian immune response will be presented for each critical step of the pathogenesis. The prevailing models of the still-enigmatic primary niche and the anatomical location where bacteria reside, persist, and are periodically seeded into the bloodstream to cause the typical relapsing Bartonella spp. bacteremia will also be critically discussed. The review will end up with a discussion of the ability of Bartonella spp., namely Bartonella henselae, Bartonella quintana, and Bartonella bacilliformis, to induce tumor-like vascular deformations in humans having compromised immune response such as in patients with AIDS.

Evolutionary microbial genomics: insights into bacterial host adaptation

Host-adapted bacteria include mutualists and pathogens of animals, plants and insects. Their study is therefore important for biotechnology, biodiversity and human health. The recent rapid expansion in bacterial genome data has provided insights into the adaptive, diversifying and reductive evolutionary processes that occur during host adaptation. The results have challenged many pre-existing concepts built from studies of laboratory bacterial strains. Furthermore, recent studies have revealed genetic changes associated with transitions from parasitism to mutualism and opened new research avenues to understand the functional reshaping of bacteria as they adapt to growth in the cytoplasm of a eukaryotic host.

Combining culture techniques for Bartonella: the best of both worlds

In this study we compared some common Bartonella culturing methodologies using four diverse species causing human illnesses. Based on a review of the literature, we focused on three major inconsistencies between protocols: base medium, cell coculture, and temperature. Our data showed that Bartonella tamiae demonstrated temperature-dependent growth limitations between common culturing conditions only 2°C apart. Additionally, growth of B. quintana was significantly enhanced by the presence of mammalian cell coculture under mammalian cell culture conditions; however, when the medium was modified to incorporate insect cell culture-based medium, coculturing with mammalian cells was no longer needed. In this study, we were able to overcome these temperature- and cell-dependent limitations and accommodate all of the strains tested by combining mammalian cell culture-based medium with insect cell culture-based medium.

Analysis of a novel insect cell culture medium-based growth medium for Bartonella species

Human- and animal-pathogenic Bartonella species are fastidious and slow-growing bacteria difficult to isolate and cultivate. We describe a novel, easy-to-prepare liquid medium for the fast and reliable growth of several Bartonella spp. that does not affect bacterial protein expression patterns or interactions with host cells.

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.

Laboratory diagnosis of Bartonella infections

Bartonella species are pathogens of emerging and reemerging significance, causing a wide array of clinical syndromes. In North America and Europe, they are increasingly recognized as a cause of culture negative endocarditis, neuroretinitis, and disease among homeless, HIV-infected, and other immunosuppressed individuals. In South America, bartonellosis continues to plague those in endemic regions and poses a significant threat to travelers in these areas. As the clinician is increasingly faced with these illnesses, which may be difficult to diagnose, laboratory techniques to confirm or refute the diagnosis are becoming increasingly important. Culture methods have improved over the past decade demonstrating increased sensitivity, but still require prolonged periods before isolation of the organism. Specimen handling, media selection, and growth conditions all may affect results and must be optimized in order to provide the highest likelihood of recovering the organism. Pure culture of the bacteria not only provides morphologic information, but also provides material for further diagnostic testing. Work with liquid media, which may provide a more rapid means of cultivation has shown some promise and should continue to be pursued. Improved blood culture techniques were a primary factor in the discovery of Bartonella endocarditis and continued improvements will likely demonstrate further clinical insights. Serologic testing for B henselae infections has become the cornerstone of clinical diagnosis, replacing the skin test that was poorly standardized and posed a potential risk to the patient. Immunofluorescence assays have been well characterized and validated in clinical trials, however they are not universally available. Vero cell cocultivated antigens appear to provide higher sensitivity and specificity when compared with agar-derived antigens. IFA assays are inherently difficult to perform, requiring significant expertise to provide reproducible results. On the contrary, enzyme immunoassays offer ease of use and a high level of reproducibility, however ideal antigens for use in the diagnosis of Bartonella infections have not been clearly identified. Continued work to define antigenic targets of the human response to infection and incorporation of these into a widely available EIA will provide a cost-effective tool for the clinician and epidemiologist alike. Due to the close phylogenetic relationship of B henselae and B quintana, differentiation between these species by serologic means may prove difficult. Molecular techniques including PCR offer high sensitivity and specificity, rapid availability of information, and the ability to differentiate Bartonella organisms at the highest level. Results of studies to date are promising and as methods are refined it will be important to conduct clinical studies to define the role of these assays. In disseminated Bartonella infections such as bacillary angiomatosis, peliosis, endocarditis, and urban trench fever, PCR currently offers the ability to establish the diagnosis when other tests may be unrevealing. For CSD, this technique should be used as a confirmatory technique when the diagnosis is unclear by other means. PCR analysis of blood specimens offers a minimally invasive approach to diagnosis, but clinical data are scarce and further studies are needed. As DNA microarrays move into the clinical arena, specific hybridization probes may allow improved identification and differentiation of Bartonellae at the molecular level.

Improved culture from lymph nodes of patients with cat scratch disease and genotypic characterization of Bartonella henselae isolates in Australia

Over a 4-year period we detected Bartonella henselae isolates in 104 of 297 specimens (35.1%) from Australian patients clinically suspected of having cat scratch disease by amplification of a fragment of the htrA gene. We isolated 17 B. henselae strains (20.5%) from the 83 PCR-positive human specimens available for culture. Our culture method was based on prolonged incubation in a moist atmosphere of blood agar to which hemin was added. We obtained more B. henselae isolates than the number of all other isolates from lymph nodes reported in the literature. In order to identify and study the genetic variation of Australian B. henselae isolates, we determined the sequence of a fragment of the pap31 gene from our 17 human isolates and also from 8 Australian cat isolates. Thirteen of the human B. henselae isolates belonged to the Houston genotype, variant Houston-1 (76.5%), and four belonged to the Marseille genotype, variant CAL-1 (23.5%). In contrast, seven cat isolates were classified as B. henselae Marseille, variant CAL-1 (87.5%), and one was classified as B. henselae Houston, variant Houston-1 (12.5%). Our study describes an efficient culture method for the diagnosis of cat scratch disease and contributes to the description of the genotypic distribution of B. henselae in Australia.

Identification, characterization, and functional analysis of a gene encoding the ferric uptake regulation protein in Bartonella species

Environmental iron concentrations coordinately regulate transcription of genes involved in iron acquisition and virulence via the ferric uptake regulation (fur) system. We identified and sequenced the fur gene and flanking regions of three Bartonella species. The most notable difference between Bartonella Fur and other Fur proteins was a substantially higher predicted isoelectric point. No promoter activity or Fur autoregulation was detected using a gfp reporter gene fused to the 204 nucleotides immediately upstream of the Bartonella fur gene. Bartonella henselae fur gene expression complemented a Vibrio cholerae fur mutant.

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.

Detection of selected fastidious bacteria

The intent of this article is to describe the optimal methods for culture recovery of 7 fastidious bacteria: Legionella species, Brucella species, Francisella tularensis, Leptospira species, Borrelia burgdorferi, Bartonella species, and Bordetella species. These organisms share much in common beyond the fact that their genus names all end in the letter "a." Culture recovery of these organisms, even from adequate clinical specimens, is logistically demanding, often costly, and lacking in both timeliness and sensitivity. In addition, there is generally no need to recover culture isolates on which to perform antimicrobial susceptibility tests because these 7 bacteria are nearly uniformly susceptible to specific, clinically useful antimicrobial agents and because, for some of them, susceptibility tests of proven reliability have not yet been devised. Perhaps for these reasons, alternative, more rapid, direct diagnostic approaches have been developed that are based on either immunochemical or nucleic-acid detection methods. These methods have generally served to supplant culture as a primary diagnostic modality. Situations exist, however, in which culture may be desirable, if not necessary, to establish a definitive diagnosis of infection with these 7 organisms. This review attempts to summarize how best to proceed in those cases.

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.

Bartonella henselae neuroretinitis in cat scratch disease. Diagnosis, management, and sequelae

OBJECTIVE

This study aimed to report the long-term outcomes of patients treated with an antibiotic drug combination for Bartonella henselae neuroretinitis.

DESIGN

The study design was a retrospective case series.

PARTICIPANTS

Seven consecutive patients with neuroretinitis and cat scratch disease participated.

INTERVENTIONS

Patients underwent medical and ophthalmic evaluations. Blood cultures were obtained, and B. henselae antibody titers were measured. Tuberculosis, Lyme, toxoplasmosis, syphilis, and sarcoidosis were excluded. Patients received oral doxycycline 100 mg and rifampin 300 mg twice daily for 4 to 6 weeks and were observed for an average of 16 months (range, 10-24 months). Formal electrophysiologic testing was performed in three patients after resolution of neuroretinitis.

MAIN OUTCOME MEASURES

The changes in ocular inflammation and visual function associated with treatment were recorded. Follow-up examinations and electrophysiologic testing documented sequelae.

RESULTS

Patients presented following cat exposure with fever, malaise, and blurred vision. Decreased visual acuity (ranging from 20/40 to counting fingers) frequently was associated with dyschromatopsia and afferent pupillary defects. Ophthalmoscopic analysis showed signs of neuroretinitis, including nerve fiber layer hemorrhages, cotton-wool spots, multiple discrete lesions in the deep retina, and stellate macular exudates. B. henselae infection was confirmed with positive blood cultures or elevated immunofluorescent antibody titers or both. Therapy appeared to promote resolution of neuroretinitis, restoration of visual acuity, and clearance of bacteremia. After 1 to 2 years, two eyes had residual disc pallor, afferent pupillary defects, retinal pigmentary changes, and mildly decreased visual acuity. Electrophysiologic studies showed that when compared to the fellow eye, affected eyes had subnormal contrast sensitivity, abnormal color vision, and abnormal visually evoked potentials. Conversely, electroretinograms were normal in all subjects.

CONCLUSIONS

B. henselae is a cause of neuroretinitis in cat scratch disease. Compared to historic cases, doxycycline and rifampin appeared to shorten the course of disease and hasten visual recovery. Long-term prognosis is good, but some individuals may acquire a mild postinfectious optic neuropathy.

Heat shock response and groEL sequence of Bartonella henselae and Bartonella quintana

Transmission of Bartonella species from ectoparasites to the mammalian host involves adaptation to thermal and other forms of stress. In order to better understand this process, the heat shock response of Bartonella henselae and Bartonella quintana was studied. Cellular proteins synthesized after shift to higher temperatures were intrinsically labelled with [25S]methionine and analysed by gel electrophoresis and fluorography. The apparent molecular masses of three of the major heat shock proteins produced by the two Bartonella species were virtually identical, migrating at 70, 60 and 10 kDa. A fourth major heat shock protein was larger in B. quintana (20 kDa) than in B. henselae (17 kDa). The maximum heat shock response in B. quintana and B. henselae was observed at 39 degrees C and 42 degrees C, respectively. The groEL genes of both Bartonella species were amplified, sequenced and compared to other known groEL genes. The phylogenetic tree based on the groEL alignment places B. quintana and B. henselae in a monophyletic group with Bartonella bacilliformis. The deduced amino acid sequences of Bartonella GroEL homologues contain signature sequences that are uniquely shared by members of the Gram-negative alpha-purple subdivision of bacteria, which live within eukaryotic cells. Recombinant His6-GroEL fusion proteins were expressed in Escherichia coli to generate specific rabbit antisera. The GroEL antisera were used to confirm the identity of the 60 kDa Bartonella heat shock protein. These studies provide a foundation for evaluating the role of the heat shock response in the pathogenesis of Bartonella infection.

Current knowledge of Bartonella species

Bartonella species are now considered emerging pathogens. Of the 11 currently recognized species, four have been implicated in human disease, although only two have been encountered in Europe. Bartonella quintana infections are now being diagnosed among the urban homeless and deprived, manifesting as trench fever, and Bartonella henselae has been shown to be the causative agent of cat scratch disease. Both species also cause a variety of HIV-associated infections, including bacillary anglomatosis. However, perhaps the most significant presentation of bartonellae infection is culture-negative endocarditis. The epidemiologies of Bartonella infections are poorly understood; most Bartonella henselae infections are probably acquired from infected cats, either directly by contact with a cat or indirectly via fleas. No animal reservoir has been implicated for Bartonella quintana; however, infection can be transmitted via the human body louse. Diagnosis of Bartonella infections can be made using histological or microbiological methods. The demonstration of specific antibodies may be useful in some instances, although certainly not in all. Cultivation of Bartonella is difficult, as the bacteria are extremely fastidious. Polymerase chain reaction-based or immunological methods for the detection of bartonella in infected tissues have proven useful. Clinical relapse is often associated with Bartonella infections despite a wide range of prescribed regimens. Only aminoglycosides display in vitro bactericidal activity against intracellular Bartonella species; therefore, they are recommended for treatment of Bartonella infections.

Bartonella spp. as emerging human pathogens

Members of the genus Bartonella (formerly Rochalimaea) were virtually unknown to modern-day clinicians and microbiologists until they were associated with opportunistic infections in AIDS patients about 6 years ago. Since that time, Bartonella species have been associated with cat scratch disease, bacillary angiomatosis, and a variety of other disease syndromes. Clinical presentation of infection with Bartonella ranges from a relatively mild lymphadenopathy with few other symptoms, seen in cat scratch disease, to life-threatening systemic disease in the immunocompromised patient. In some individuals, infection manifests as lesions that exhibit proliferation of endothelial cells and neovascularization, a pathogenic process unique to this genus of bacteria. As the spectrum of disease attributed to Bartonella is further defined, the need for reliable laboratory methods to diagnose infections caused by these unique organisms also increases. A brief summary of the clinical presentations associated with Bartonella infections is presented, and the current status of laboratory diagnosis and identification of these organisms is reviewed.

Isolation of Bartonella (Rochalimaea) henselae: effects of methods of blood collection and handling

Bartonella (Rochalimaea) henselae causes cat-scratch disease, bacillary angiomatosis, peliosis hepatis, and fever in humans. B. henselae can be difficult to culture axenically, and as many as 5 weeks may be required before colonies are visible. We compared how different methods of blood collection and handling affect isolation of this pathogen. Blood specimens from B. henselae-infected cats were collected in both EDTA and Isolator blood-lysis tubes and were subsequently plated onto rabbit blood-brain heart infusion agar by using three different schedules: plating immediately, plating after 24 h at 25 degrees C, and plating after 26 days at -65 degrees C. Colonies were counted 14 and 35 days after plating. Blood collected in tubes containing EDTA, frozen at -65 degrees C, and then plated on blood agar yielded a median of 60,000 CFU/ml, compared with 25,333 CFU/ml after collection in the Isolator tubes (P < 0.01). Frozen blood yielded the largest number of B. henselae colonies for any of the schedules tested. These results support previous observations that the Isolator system is more sensitive than tubes containing EDTA for isolation of B. henselae and suggest that, for cat blood, collection in tubes containing EDTA and subsequent freezing may further improve the sensitivity of detection of B. henselae.

Isolation of Bartonella quintana from an HIV-positive patient with bacillary angiomatosis

Bartonella quintana was grown from a lysis-centrifugation blood culture of an HIV-positive man who presented with lesions of bacillary angiomatosis in skin and bones. The isolate was identified by sodium dodecylsulfate-polyacrylamide gel electrophoresis, 16S rRNA gene sequencing, and amplification of the enterobacterial repetitive intergenic consensus sequences.

Bartonella (Rochalimaea) infections: beyond cat scratch

Five species of Bartonella have been found to infect humans, henselae, quintana, elizabethae, bacilliformis, and vinsonii. The most common of these in North America are Bartonella quintana and Bartonella henselae, the agents of trench fever, bacillary angiomatosis, and parenchymal peliosis, and in the case of B. henselae cat-scratch disease. B. bacilliformis is endemic in Peru and Ecuador, where it causes oroya fever or Carrion's disease. New methods of diagnosing Bartonella infections have resulted in increased recognition of the many manifestations of these infections. Early recognition is crucial, as these are potentially fatal opportunistic infections that usually respond rapidly to appropriate antimicrobial therapy.