Unraveling mysteries associated with cat-scratch disease, bacillary angiomatosis, and related syndromes

Evaluation of the available animal models for Bartonella infections

The diseases caused by the Bartonella genus of bacteria are clinically diverse, and can be challenging to cure. The study of bartonellosis has been hampered by the lack of a suitable animal model. Preclinical studies for novel therapeutics and a competent host for vector transmission studies are needed to fill critical knowledge gaps. The studies included here are a representation of in vivo Bartonella research and the corresponding challenges. This review examines the current state of available animal models by assessing the success of various model species and strains in Bartonella infection. With a focus on the strengths and weaknesses of current animal models, the importance of these models for improvement of human health and veterinary care is emphasized.

Evolution of in-hospital patient characteristics and predictors of death in the COVID-19 pandemic across four waves: are they moving targets with implications for patient care?

Objectives

The aim of this work was to study characteristics, outcomes and predictors of all-cause death in inpatients with SARS-CoV-2 infection across the pandemic waves in one large teaching hospital in Italy to optimize disease management.

Methods

All patients with SARS-CoV-2 infection admitted to our center from March 2020 to June 2022 were included in this retrospective observational cohort study. Both descriptive and regression tree analyses were applied to identify factors influencing all-cause mortality.

Results

527 patients were included in the study (65.3% with moderate and 34.7% with severe COVID-19). Significant evolutions of patient characteristics were found, and mortality increased in the last wave with respect to the third wave notwithstanding vaccination. Regression tree analysis showed that in-patients with severe COVID-19 had the greatest mortality across all waves, especially the older adults, while prognosis depended on the pandemic waves in patients with moderate COVID-19: during the first wave, dyspnea was the main predictor, while chronic kidney disease emerged as determinant factor afterwards.

Conclusion

Patients with severe COVID-19, especially the older adults during all waves, as well as those with moderate COVID-19 and concomitant chronic kidney disease during the most recent waves require more attention for monitoring and care. Therefore, our study drives attention towards the importance of co-morbidities and their clinical impact in patients with COVID-19 admitted to hospital, indicating that the healthcare system should adapt to the evolving features of the epidemic.

Bartonella Endocarditis in Spain: Case Reports of 21 Cases

Blood culture negative endocarditis (BCNE) is frequent in infective endocarditis (IE). One of the causes of BCNE is fastidious microorganisms, such as Bartonella spp. The aim of this study was to describe the epidemiologic, clinical characteristics, management and outcomes of patients with Bartonella IE from the “Spanish Collaboration on Endocarditis-Grupo de Apoyo al Manejo de la Endocarditis infecciosa en España (GAMES)”cohort. Here we presented 21 cases of Bartonella IE. This represents 0.3% of a total of 5590 cases and 2% of the BCNE from the GAMES cohort. 62% were due to Bartonella henselae and 38% to Bartonella quintana. Cardiac failure was the main presenting form (61.5% in B. hensalae, 87.5% in B. quintana IE) and the aortic valve was affected in 85% of the cases (76% in B. henselae, 100% in B. quintana IE). Typical signs such as fever were recorded in less than 40% of patients. Echocardiography showed vegetations in 92% and 100% of the patients with B. henselae and B. quintana, respectively. Culture was positive only in one patient and the remaining were diagnosed by serology and PCR. PCR was the most useful tool allowing for diagnosis in 16 patients (100% of the studied valves). Serology, at titers recommended by guidelines, only coincided with PCR in 52.4%. Antimicrobial therapy, in different combinations, was used in all cases. Surgery was performed in 76% of the patients. No in-hospital mortality was observed. One-year mortality was 9.4%. This article remarks the importance for investigating the presence of Bartonella infection as causative agent in all BCNE since the diagnosis needs specific microbiological tools and patients could benefit of a specific treatment.

Bartonella spp. - a chance to establish One Health concepts in veterinary and human medicine

Infectious diseases remain a remarkable health threat for humans and animals. In the past, the epidemiology, etiology and pathology of infectious agents affecting humans and animals have mostly been investigated in separate studies. However, it is evident, that combined approaches are needed to understand geographical distribution, transmission and infection biology of “zoonotic agents”. The genus Bartonella represents a congenial example of the synergistic benefits that can arise from such combined approaches: Bartonella spp. infect a broad variety of animals, are linked with a constantly increasing number of human diseases and are transmitted via arthropod vectors. As a result, the genus Bartonella is predestined to play a pivotal role in establishing a One Health concept combining veterinary and human medicine.

Feline hemotropic mycoplasmas

OBJECTIVE

To describe the current understanding of the etiology, pathogenesis, diagnosis, and treatment of feline hemotropic mycoplasmosis (feline infectious anemia).

DATA SOURCES

Manuscripts published on hemotropic mycoplasmosis in cats and other animal species, based on a search of PubMed using the search terms 'hemoplasmas,''haemoplasmas,''hemotropic,''haemotropic,' and 'Haemobartonella,' as well as references published within manuscripts accessed.

HUMAN DATA SYNTHESIS

Although hemotropic bacteria such as Bartonella bacilliformis have been recognized in humans for over 100 years, it has only been in recent years that some of these have been identified as hemotropic mycoplasmas.

VETERINARY DATA SYNTHESIS

Three species of hemotropic mycoplasmas have been documented in cats worldwide, Mycoplasma haemofelis, 'Candidatus Mycoplasma turicensis,' and 'Candidatus Mycoplasma haemominutum.' These organisms were previously known as Haemobartonella felis, but are now known to be mycoplasmas. M. haemofelis is the most pathogenic species, and causes anemia in immunocompetent cats. Although 'Candidatus Mycoplasma turicensis' and 'Candidatus Mycoplasma haemominutum' may be more capable of causing anemia in immunosuppressed cats, their pathogenicity remains controversial. Assays based on polymerase chain reaction technology are the most sensitive and specific diagnostic tests available for these organisms, because they remain uncultivable in the laboratory setting. Blood smears are unreliable for diagnosis of hemoplasmosis because of their lack of sensitivity and specificity.

CONCLUSIONS

Cats presenting to emergency/critical care specialists with hemolytic anemia should be tested using polymerase chain reaction assays for hemotropic mycoplasmas before instituting antimicrobial therapy. Positive test results for M. haemofelis suggest involvement of this organism in hemolytic anemia. Other differential diagnoses for hemolytic anemia should be considered in cats testing positive for 'Candidatus Mycoplasma turicensis' and 'Candidatus Mycoplasma haemominutum,' because the presence of these organisms is not always associated with anemia. Blood from infected cats should be handled with care because of the potential zoonotic nature of this infection.

Guidelines for the Prevention and Treatment of Opportunistic Infections among HIV-exposed and HIV-infected children: recommendations from CDC, the National Institutes of Health, the HIV Medicine Association of the Infectious Diseases Society of America, the Pediatric Infectious Diseases Society, and the American Academy of Pediatrics

This report updates and combines into one document earlier versions of guidelines for preventing and treating opportunistic infections (OIs) among HIV-exposed and HIV-infected children, last published in 2002 and 2004, respectively. These guidelines are intended for use by clinicians and other health-care workers providing medical care for HIV-exposed and HIV-infected children in the United States. The guidelines discuss opportunistic pathogens that occur in the United States and one that might be acquired during international travel (i.e., malaria). Topic areas covered for each OI include a brief description of the epidemiology, clinical presentation, and diagnosis of the OI in children; prevention of exposure; prevention of disease by chemoprophylaxis and/or vaccination; discontinuation of primary prophylaxis after immune reconstitution; treatment of disease; monitoring for adverse effects during treatment; management of treatment failure; prevention of disease recurrence; and discontinuation of secondary prophylaxis after immune reconstitution. A separate document about preventing and treating of OIs among HIV-infected adults and postpubertal adolescents (Guidelines for the Prevention and Treatment of Opportunistic Infections in HIV-Infected Adults and Adolescents) was prepared by a working group of adult HIV and infectious disease specialists. The guidelines were developed by a panel of specialists in pediatric HIV infection and infectious diseases (the Pediatric Opportunistic Infections Working Group) from the U.S. government and academic institutions. For each OI, a pediatric specialist with content-matter expertise reviewed the literature for new information since the last guidelines were published; they then proposed revised recommendations at a meeting at the National Institutes of Health (NIH) in June 2007. After these presentations and discussions, the guidelines underwent further revision, with review and approval by the Working Group, and final endorsement by NIH, CDC, the HIV Medicine Association (HIVMA) of the Infectious Diseases Society of America (IDSA), the Pediatric Infectious Disease Society (PIDS), and the American Academy of Pediatrics (AAP). The recommendations are rated by a letter that indicates the strength of the recommendation and a Roman numeral that indicates the quality of the evidence supporting the recommendation so readers can ascertain how best to apply the recommendations in their practice environments. An important mode of acquisition of OIs, as well as HIV infection among children, is from their infected mother; HIV-infected women coinfected with opportunistic pathogens might be more likely than women without HIV infection to transmit these infections to their infants. In addition, HIV-infected women or HIV-infected family members coinfected with certain opportunistic pathogens might be more likely to transmit these infections horizontally to their children, resulting in increased likelihood of primary acquisition of such infections in the young child. Therefore, infections with opportunistic pathogens might affect not just HIV-infected infants but also HIV-exposed but uninfected infants who become infected by the pathogen because of transmission from HIV-infected mothers or family members with coinfections. These guidelines for treating OIs in children therefore consider treatment of infections among all children, both HIV-infected and uninfected, born to HIV-infected women. Additionally, HIV infection is increasingly seen among adolescents with perinatal infection now surviving into their teens and among youth with behaviorally acquired HIV infection. Although guidelines for postpubertal adolescents can be found in the adult OI guidelines, drug pharmacokinetics and response to treatment may differ for younger prepubertal or pubertal adolescents. Therefore, these guidelines also apply to treatment of HIV-infected youth who have not yet completed pubertal development. Major changes in the guidelines include 1) greater emphasis on the importance of antiretroviral therapy for preventing and treating OIs, especially those OIs for which no specific therapy exists; 2) information about the diagnosis and management of immune reconstitution inflammatory syndromes; 3) information about managing antiretroviral therapy in children with OIs, including potential drug--drug interactions; 4) new guidance on diagnosing of HIV infection and presumptively excluding HIV infection in infants that affect the need for initiation of prophylaxis to prevent Pneumocystis jirovecii pneumonia (PCP) in neonates; 5) updated immunization recommendations for HIV-exposed and HIV-infected children, including hepatitis A, human papillomavirus, meningococcal, and rotavirus vaccines; 6) addition of sections on aspergillosis; bartonella; human herpes virus-6, -7, and -8; malaria; and progressive multifocal leukodystrophy (PML); and 7) new recommendations on discontinuation of OI prophylaxis after immune reconstitution in children. The report includes six tables pertinent to preventing and treating OIs in children and two figures describing immunization recommendations for children aged 0--6 years and 7--18 years. Because treatment of OIs is an evolving science, and availability of new agents or clinical data on existing agents might change therapeutic options and preferences, these recommendations will be periodically updated and will be available at http://AIDSInfo.nih.gov.

Evaluation of an in-house cat scratch disease IgM ELISA to detect Bartonella henselae in a routine laboratory setting

Cat scratch disease (CSD) is caused by Bartonella henselae infection and is a common cause of regional lymphadenopathy. The diagnosis of CSD largely depends on serology, but detection of B. henselae in an affected lymph node by PCR is also an important diagnostic tool. We evaluated an IgM in-house ELISA protocol and analyzed its performance in routine CSD serology. Serum samples from PCR-positive patients (n = 126), PCR-negative patients (n = 123), and age-matched controls (n = 126) were used for evaluation. The sensitivity of the IgM ELISA was only 56%, showing that the performance of B. henselae serology under routine laboratory settings is low, probably caused by the wide variability in disease duration in patients suspected of CSD whose samples were submitted to our laboratory. Most patients (46%) with a positive IgM response were between 0 and 20 years of age. We conclude that the serodiagnosis of B. henselae is hampered by the low sensitivity and specificity of the assays when used in a routine laboratory setting. For this reason, a negative IgM or PCR result can never exclude CSD, especially with late sample collection.

Production of recombinant Bartonella henselae 17-kDa protein for antibody-capture enzyme-linked immunosorbent assay

The Bartonella henselae 17-kDa protein was expressed in a prokaryotic expression system as a histidine-tagged fusion protein and was purified. The target gene was cloned into a recombinant expression construct, pTri-17kd. The expressed protein was purified to near homogeneity by a nickel-agarose column chromatography. Protein recovery was estimated to be 2.9 mg from 100 mL of bacterial culture. The purified 17-kDa protein was recognized by serum from patients infected with B. henselae and Bartonella quintana, suggesting antigenic integrity. The sensitivity and specificity of the IgG enzyme-linked immunosorbent assay (ELISA) relative to immunofluorescent antibody assay testing were 71.1% and 93.0%, respectively. According to the receiver operating characteristic curve analysis, the area under the curve was 0.823. These results indicate that the expressed 17-kDa protein is a suitable source of antigen for development of an antibody-capture ELISA for the detection of antibodies to B. henselae.

A prospective study of Cat-Scratch Disease in Lima-Peru

Cat-Scratch Disease (CSD) is a benign lymphadenitis that may progress to severe or recurrent forms, and it is occasionally associated with morbidity. Between January of 1998 and March of 1999, forty-three suspected CSD patients were assessed in the Hospital Cayetano Heredia and the Instituto de Salud del Niño, in Lima, Peru. Twelve patients had a confirmed diagnosis, 8 of whom were women, and the mean age was 10 years old. The majority (53%) of the cases were encountered in the summer. All patients reported having had contact with cats. Fever, malaise, lymphadenopathy and skin lesions were the most frequent clinical features. Twelve patients had indirect immunofluorescence antibody test titers of between 1/50 and 1/800 for Bartonella henselae and Bartonella clarridgeiae. Two lymph node biopsies were histologically compatible with CSD. No positive blood cultures could be obtained. This is the first Peruvian prospective study able to identify B. henselae and B. clarridgeiae in pediatric patients.

Parinaud'S oculoglandular syndrome associated with paracoccidioidomycosis

The authors report one case of Parinaud's oculoglandular syndrome associated with Paracoccidioides brasiliensis infection. No other medical report of this condition was found in the medical literature available at Index Medicus and Medline. The eye involvement has been rather uncommon in paracoccidioidomycosis and this report emphasizes the possibility of this kind of presentation making it also necessary to include paracoccidioidomycosis among the several known causes of Parinaud's oculoglandular syndrome.

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.

Bartonella henselae, B. quintana, and B. bacilliformis: historical pathogens of emerging significance

Bartonella species were virtually unrecognized as modern pathogens of humans until the last decade. However, identification of Bartonella species as the agents of cat-scratch disease, bacillary angiomatosis, urban trench fever, and possible novel presentations of Carrion's disease has left little doubt of the emerging medical importance of this genus of organisms. The three primary human pathogenic bartonellae, Bartonella bacilliformis (Carrion's disease), B. henselae (cat-scratch disease), and B. quintana (trench fever), present noteworthy comparisons in the epidemiology, natural history, pathology, and host-microbe interaction that this review will briefly explore.

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.

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.

Ocular manifestations of cat-scratch disease

Bartonella henselae has only recently been isolated, characterized, and found to be the principal cause of cat-scratch disease (CSD). The availability of specific serologic investigations has allowed the recognition of a spectrum of ocular CSD syndromes that previously were ill defined and considered idiopathic. The primary inoculation complex causing regional lymphadenopathy is represented in the eye by Parinaud's oculoglandular syndrome; B. henselae is the most common cause. Leber's neuroretinitis has been identified for 80 years, and new data suggest that it is commonly a manifestation of CSD; the extent of the association remains to be determined. CSD optic neuritis is also described. The vitreoretinal manifestations include anterior uveitis, vitritis, pars planitis, focal retinal vasculitis, a characteristic retinal white spot syndrome, Bartonella retinitis, branch retinal arteriolar or venular occlusions, focal choroiditis, serous retinal detachments, and peripapillary angiomatous lesions. The pattern of ocular disease in AIDS-associated B. henselae infections is poorly delineated; unusual manifestations include conjunctival and retinal bacillary angiomatosis. The benefit of antimicrobial therapy for CSD in immunocompetent individuals has been difficult to establish, partly because most infections are self limited. Empirically, azithromycin, ciprofloxacin, rifampin, parenteral gentamicin, or trimethoprim-sulfamethoxazole provide the best therapeutic choices to minimize damage to the eye.

Vaccination of cats against emerging and reemerging zoonotic pathogens

Many of the emerging infectious agents that threaten the human population are either directly zoonotic or involve animals, rather than humans, as their primary reservoir in nature. Vaccination of animals may be an important consideration for control of some of these diseases, and this review has specifically focused on the concept of vaccinating cats in the prevention of infection with T. gondii, B. henselae, and H. pylori. If we return to the considerations that were presented in Table III, T. gondii is really the only one of these three agents for which each of these "criteria" for vaccination is fulfilled at the present time. However, cats clearly play an important role in the epidemiology of infection with B. henselae and this is an organism for which we probably will and should see a vaccine for widespread and routine use in cats.

Use of the cell division protein FtsZ as a means of differentiating among Bartonella species

Genes coding for homologs of the highly conserved cell division protein FtsZ were isolated from Bartonella henselae and Bartonella quintana, the causative agents of cat scratch disease and trench fever, respectively. DNA fragments coding for the ftsZ open reading frames (ORFs) were cloned into Escherichia coli following PCR amplification with primers based on the ftsZ sequence of the closely related species Bartonella bacilliformis. The amino acid sequences predicted from the cloned B. henselae and B. quintana ftsZ ORFs are 81 to 83% identical to the corresponding protein in B. bacilliformis. Like the FtsZ protein of B. bacilliformis, the B. henselae and B. quintana homologs are about twice as large as the FtsZ proteins reported in most other organisms. Localized sequence differences within the C-terminal coding regions of the Bartonella ftsZ genes were used as the basis for species-specific identification of these organisms at both the DNA and protein levels. Oligonucleotide primers which permit the amplification of an ftsZ fragment from each of the Bartonella species without amplifying DNA from the other two species were designed. Anti-FtsZ antisera raised in rabbits against synthetic peptides corresponding to the relatively divergent C-terminal regions were shown via Western blot analysis to react only with the FtsZ protein from the cognate Bartonella species. These observations raise the possibility that the differences in ftsZ sequences can be used as the basis for diagnostic tests to differentiate among these closely related pathogens.

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.

Cloning, functional expression, and complementation analysis of an inorganic pyrophosphatase from Bartonella bacilliformis

We have cloned the inorganic pyrophosphatase gene (ppa) from the facultative intracellular pathogen Bartonella bacilliformis and characterized its encoded product. The 531-bp gene is located approximately 1 kb downstream of, and in opposite orientation to, the invasion-associated locus (ialAB) of B. bacilliformis. The predicted protein encoded by ppa is 177 amino acid residues, which is in agreement with in vitro and in vivo synthesis of a protein with an apparent molecular mass of 22-23 kDa. The predicted B. bacilliformis pyrophosphatase (PPase) sequence is 53% identical and 85% similar to the E. coli PPase (EC 3.6.1.1), and contains all 12 of the amino acid residues implicated in the catalytic active site. The isolated B. bacilliformis PPase exhibits an activity of 51 +/- 2 mumol PO4 released/(mg protein.min) at 28 degrees C and pH 8, and is sensitive to inhibition by Ca2+. In keeping with other prokaryotic PPases, B. bacilliformis PPase activity occurs from pH 6 to 10 (optimal pH = 8) and demonstrates high thermostability in the presence of Mg2+ (highest activity at 55 degrees C, relative activity = 80 +/- 3% at pH 8). The cloned B. bacilliformis ppa is able to genetically complement a ppa- mutant strain of E. coli.

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.

The expanding spectrum of Bartonella infections: II. Cat-scratch disease

Recent advancements and developments in molecular biotechnology have allowed more precise reclassification of many microorganisms. With the use of these new taxonomy tools, several organisms previously thought to belong to other genera have been recently described as bartonellae. Of the 11 organisms now described as Bartonella spp., only four have been shown to be pathogenic for humans. Table 1 lists the four Bartonella human pathogens along with the their known epidemiology and the scope and range of disease associated with each. All are now considered to be bacteria and can be grown on blood-enriched agar although primary isolation in some may best be achieved in cell tissue culture. B. bacilliformis infection is limited to certain geographic regions in South America where the only human reservoir and the sandfly vector(s) that spreads the disease reside together. Specific antibiotic treatment is dramatically effective in treating the highly fatal, acute intraerythrocytic hemolytic form of the disease, but their effectiveness in treating the vascular proliferative forms (verruga peruana) or the chronic asymptomatic, bacteremic, carrier state of the disease has not been effective. This disease should remain confined to its present endemic geographic areas in South American unless asymptomatic bacteremic persons from these areas migrate to areas where sandflies and humans exist that are capable of establishing this infection in new endemic areas. B. quintana and B. henselae cause a wide range of clinical diseases in humans, the type and extent of which varies significantly with the immune status of the host. In immunocompetent hosts the pathologic response is granulomatous, suppurative, extracellular and intracellular, generally self-limited and usually unresponsive to antibiotic treatment, even to those drugs to which the organism is shown to be sensitive in vitro. In contrast, in immunocompromised hosts the pathologic response is vasculoproliferative, organisms may be seen intracellularly but they are often seen in abundance in extracellular clumps and infection is usually progressive and fatal unless treated. In these patients clinical response to treatment with drugs that are effective in vitro against these organisms has usually been dramatic. Of these agents those that penetrate cells and are found in high concentrations intracellularly, such as erythromycin, clarithromycin, azithromycin, rifampin, doxycycline and gentamicin, appear to be most effective. These agents not only appear to provide the most dramatic treatment response in patients with BA, BP and PRFB and other manifestations of B. henselae (and B. quintana as well) in immunocompromised persons, they appear to be the most promising agents for treatment of persons with both typical and atypical CSD. Further studies will be necessary to more clearly elucidated the mechanisms responsible for the diverse clinical presentations of infection with these organisms in human hosts relative to their immune status. In addition clarification of the epidemiology of B. elizabethae infections in humans may be helpful in understanding the nature of infection with Bartonella organisms.

Molecular approaches to the identification of unculturable infectious agents

New molecular biologic techniques, particularly representational difference analysis, consensus sequence-based polymerase chain reaction, and complementary DNA library screening, have led to the identification of several previously unculturable infectious agents. New agents have been found in tissues from patients with Kaposi's sarcoma, non-A, non-B hepatitis, hantavirus pulmonary syndrome, bacillary angiomatosis, and Whipple's disease by using these techniques without direct culture. The new methods rely on identifying subgenomic fragments from the suspected agent. After a unique nucleic acid fragment belonging to an agent is isolated from diseased tissues, the fragment can be sequenced and used as a probe to identify additional infected tissues or obtain extended portions of the agent's genome. For agents that cannot be cultured by standard techniques, these approaches have proved invaluable for identification and characterization studies. Applying these techniques to other human diseases of suspected infectious etiology may rapidly elucidate novel candidate pathogens.

Nucleotide sequence analysis of the 23S ribosomal RNA-encoding gene of Bartonella bacilliformis

We report the cloning and characterization of the 23S ribosomal RNA (rRNA)-encoding gene (rDNA) of Bartonella bacilliformis (Bb). The 2821-bp gene is preceded by an 11-nucleotide (nt) inverted repeat (IR) located 81 nt upstream in the tRNA(Ala)-23S rDNA intergenic spacer. The gene is followed by an 8-nt IR, five nt downstream in the 23S-5S rDNA intergenic spacer. The nt sequence of the Bb 23S rDNA is most similar to the 23S rDNA of Rhodopseudomonas palustris (Rp), with 85.4% sequence identity. The Bb 23S rDNA has 77.8% identity to the same gene from Escherichia coli (Ec). Secondary structure predictions indicate that the large subunit (LSU) Bb rRNA contains two smaller stem-loops at nt 1459-1544 and 1658-1685, as compared to the corresponding loops from Ec (nt 1405-1597 and 1707-1751, respectively). In addition, the Bb 23S rRNA has a large 72-nt stem-loop at nt 130-201, as compared to the Ec 18-nt stem-loop (nt 131-148). There is no Bb homologue of the 15-nt stem-loop at the 3' end of the Ec molecule (nt 2791-2805). The Bb 23S rRNA lacks the large stem-loop present in the LSU rRNA of closely related Rhodobacter sphaeroides (Rs) (nt position 1225-1331) which is thought to be involved in cleavage of 23S RNA precursor molecules into 16S and 14S rRNA species. This is the first LSU rDNA nt sequence for any member of the Bartonellaceae family.