Bartonella vinsonii subsp. arupensis as an agent of blood culture-negative endocarditis in a human

Clinicopathological differences between Bartonella and other bacterial endocarditis-related glomerulonephritis - our experience and a pooled analysis

Background

Although Staphylococcus aureus is the leading cause of acute infective endocarditis (IE) in adults, Bartonella spp. has concomitantly emerged as the leading cause of "blood culture-negative IE" (BCNE). Pre-disposing factors, clinical presentation and kidney biopsy findings in Bartonella IE-associated glomerulonephritis (GN) show subtle differences and some unique features relative to other bacterial infection-related GNs. We highlight these features along with key diagnostic clues and management approach in Bartonella IE-associated GN.

Methods

We conducted a pooled analysis of 89 cases of Bartonella IE-associated GN (54 published case reports and case series; 18 published conference abstracts identified using an English literature search of several commonly used literature search modalities); and four unpublished cases from our institution.

Results

Bartonella henselae and Bartonella quintana are the most commonly implicated species causing IE in humans. Subacute presentation, affecting damaged native and/or prosthetic heart valves, high titer anti-neutrophil cytoplasmic antibodies (ANCA), mainly proteinase-3 (PR-3) specificity, fastidious nature and lack of positive blood cultures of these Gram-negative bacilli, a higher frequency of focal glomerular crescents compared to other bacterial infection-related GNs are some of the salient features of Bartonella IE-associated GN. C3-dominant, but frequent C1q and IgM immunofluorescence staining is seen on biopsy. A "full-house" immunofluorescence staining pattern is also described but can be seen in IE -associated GN due to other bacteria as well. Non-specific generalized symptoms, cytopenia, heart failure and other organ damage due to embolic phenomena are the highlights on clinical presentation needing a multi-disciplinary approach for management. Awareness of the updated modified Duke criteria for IE, a high index of suspicion for underlying infection despite negative microbiologic cultures, history of exposure to animals, particularly infected cats, and use of send-out serologic tests for Bartonella spp. early in the course of management can help in early diagnosis and initiation of appropriate treatment.

Conclusion

Diagnosis of IE-associated GN can be challenging particularly with BCNE. The number of Bartonella IE-associated GN cases in a single institution tends to be less than IE due to gram positive cocci, however Bartonella is currently the leading cause of BCNE. We provide a much-needed discussion on this topic.

Case series of 12 Bartonella quintana endocarditis from the Southwest Indian Ocean

BACKGROUND

Bartonella spp. are fastidious bacteria frequently identified as the cause of blood culture-negative (BCN) endocarditis. However, Bartonella infections are difficult to diagnose in routine laboratory testing and their incidence is probably underestimated. We investigated the epidemiological and clinical features of Bartonella endocarditis cases diagnosed between 2009 and 2021 on Reunion Island (Southwest Indian Ocean).

METHOD

We retrospectively included all patients diagnosed with Bartonella endocarditis at Reunion Island University Hospital during this period. Endocarditis was diagnosed on the basis of microbiological findings, including serological tests (IFA) and PCR on cardiac valves, and the modified Duke criteria. We used then the multispacer typing (MST) method to genotype the available Bartonella strains.

FINDINGS

We report 12 cases of B. quintana endocarditis on Reunion Island (83.3% in men, median patient age: 32 years). All the patients originated from the Comoros archipelago. The traditional risk factors for B. quintana infection (homelessness, alcoholism, exposure to body lice) were absent in all but two of the patients, who reported head louse infestations in childhood. Previous heart disease leading to valve dysfunction was recorded in 50% of patients. All patients underwent cardiac valve surgery and antimicrobial therapy with a regimen including doxycycline. All patients presented high C-reactive protein concentrations, anemia and negative blood cultures. The titer of IgG antibodies against Bartonella sp. exceeded 1:800 in 42% of patients. Specific PCR on cardiac valves confirmed the diagnosis of B. quintana endocarditis in all patients. Genotyping by the MST method was performed on four strains detected in preserved excised valves and was contributive for three, which displayed the MST6 genotype.

CONCLUSIONS

Bartonella quintana is an important cause of infective endocarditis in the Comoros archipelago and should be suspected in patients with mitral valve dysfunction and BCN from this area.

Detection of Bartonella vinsonii, Anaplasma platys and Bartonella sp. in didelphis marsupialis, Pecari tajacu and Chelonoidis denticulate: Peru

INTRODUCTION

Evidence suggest that wildlife Infectious diseases related to wildlife are of most importance because of the agents' capacity to spill over into humans from the wild reservoir. Among them, the bacteria Bartonella spp. and Anaplasma spp. are related to this zoonotic dynamic.

OBJECTIVE

The primary goal of the present study was to determine the presence of pathogenic bacteria in kidney and liver tissues of Didelphis marsupialis; spleen, liver, and skin of Pecari tajacu; spleen, liver, and skin of Chelonoidis denticulata.

METHODOLOGY

A PCR using universal and specific primers for 16 S rRNA, of Bartonella spp. with subsequent genetic sequencing were used.

RESULTS

The results in this study indicate that Bartonella vinsonni was detected in the liver tissue of Didelphis marsupialis using both universal primers and those specific for Bartonella sp. Anaplasma platys was detected at the liver and spleen level using universal primers. Additionally, Bartonella spp. was found at the liver, spleen, and skin level in Pecari tajacu using the specific primers. Finally, using the universal and specific primers at the skin level, Bartonella spp. was evident in Chelonoidis denticulata.

CONCLUSIONS

The presence of the DNA of the Bartonella vinsonii was detected at the liver tissue in Didelphis marsupialis. DNA of the Anaplasma platys and Bartonella spp. were identified at the spleen and liver level. This study also identified that DNA Bartonella spp. was detected in Pecari tajacu skin. Finally DNA of Bartonella spp. was evident in Chelonoidis denticulate skin. The findings of this study suggest that these bacteria are present in these animals and may be responsible for outbreaks.

Bartonella Species in Cambodia, Ghana, Laos, and Peru: Results from Vector and Serosurveys

Background: Bartonella species are fastidious gram-negative vector-borne bacteria with a wide range of mammalian reservoirs. While it is understood that some species of Bartonella are human pathogens, the extent of human exposure to Bartonella species (both pathogenic and nonpathogenic) is yet to be fully understood. Materials and Methods: To this end, residual sera from participants enrolled in undifferentiated fever studies in Cambodia, Ghana, Laos, and Peru were screened for the presence of IgG antibodies against Bartonella quintana and Bartonella henselae, using the FOCUS diagnostics Dual Spot- Bartonella IgG Immunofluorescence assay. Forty-eight patients with suspected or confirmed Bartonella bacilliformis exposure or infection in Peru were screened to assess cross-reactivity of the FOCUS assay for IgG against other Bartonella species. Results: Ten of 13 patients with confirmed B. bacilliformis infection were Bartonella-specific IgG positive, and overall, 36/48 of the samples were positive. In addition, 79/206, 44/200, 101/180, and 57/100 of the samples from Peru, Laos, Cambodia, and Ghana, respectively, were Bartonella-specific IgG positive. Furthermore, ectoparasite pools from Cambodia, Laos, and Peru were tested using quantitative real-time PCR (qPCR) for the presence of Bartonella DNA. Of the sand fly pools collected in Peru, 0/196 were qPCR positive; 15/140 flea pools collected in Cambodia were qPCR positive; while 0/105 ticks, 0/22 fleas, and 0/3 louse pools collected in Laos tested positive for Bartonella DNA. Conclusion: Evidence of Bartonella in fleas from Cambodia supports the possibility that humans are exposed to Bartonella through this traditional vector. However, Bartonella species were not found in fleas, ticks, or lice from Laos, or sand flies from Peru. This could account for the lower positive serology among the population in Laos and the strictly localized nature of B. bacilliformis infections in Peru. Human exposure to the Bartonella species and Bartonella as a human pathogen warrants further investigation.

First Report of Bartonella spp. in Marsupials from Brazil, with a Description of Bartonella harrusi sp. nov. and a New Proposal for the Taxonomic Reclassification of Species of the Genus Bartonella

The genus Bartonella (Rhizobiales: Bartonellaceae) encompasses facultative intracellular Gram-negative alphaproteobacteria that parasitize mainly erythrocytes and endothelial cells, as well as macrophages, monocytes and dendritic cells. Although they can infect numerous mammal species and arthropod vectors worldwide, reports of Bartonella infections in marsupials are scarce. In fact, such agents have only been detected in marsupials and/or associated ectoparasites in Australia and the United States of America until the present moment. The present study aimed to isolate and characterize molecularly, morphologically and phenotypically Bartonella infecting free-living marsupials sampled in the Brazilian Pantanal, the largest wetland in South America. Two marsupials were captured in December 2018 and six marsupials in February 2019, totaling eight small mammals sampled: five (62.5%) Thylamys macrurus and three (37.5%) Monodelphis domestica. All blood samples were submitted to qPCR for Bartonella spp. based on the nuoG gene, a pre-enrichment liquid culture and a chocolate agar solid culture. Bartonella sp. was isolated from 3 T. macrurus and one M. domestica. One Bartonella isolate obtained from a T. macrurus blood sample (strain 117A) that showed to be closely related to the Bartonella vinsonii complex and Bartonella machadoae was selected for whole genome sequencing using a hybrid approach based on Illumina NovaSeq and Nanopore sequencing platforms. This strain showed a genome of 2.35 Mbp, with an average C + G content of 38.8%, coding for 2013 genes, and a 29 kb plasmid with an average C + G content of 34.5%. In addition, this strain exhibited an average nucleotide identity (ANI) of 85% with Bartonella species belonging to the B. vinsonii group and 91% with B. machadoae. Phylogenomic analysis based on 291 protein coding genes shared by the genomes of 53 Bartonella species positioned this strain closely to B. machadoae. This new isolated species was named Bartonella harrusi sp. nov., which was characterized as having small capnophilic, microaerophilic and aerobic rods with an absence of pili and flagella. In conclusion, the present work describes the biochemical, phenotypic and genomic characteristics of Bartonella harrusi, a new species isolated from the T. macrurus blood samples of the Brazilian Pantanal. Finally, a review of the taxonomic classification of members of the genus Bartonella is proposed, based on the ANI values accessed by whole genome sequencing analyses.

A Review of Bartonella Infections in California-Implications for Public and Veterinary Health

Bartonella are vector-transmitted, intracellular bacteria that infect a wide variety of blood-feeding arthropods and their vertebrate hosts. In California, more than 13 species of Bartonella have been described from companion animals, livestock, and wildlife, of which four have been associated with human disease. Infections in humans cause a range of symptoms from relatively mild to severe, especially in immunocompromised individuals. Exposure to infected domestic animals and wildlife, and their ectoparasites, may increase the risk of cross-species transmission. The objective of this review was to compile and summarize published materials on human and animal Bartonella infections in California. Medical and veterinary case reports of bartonellosis were highlighted in an effort to increase the awareness of this poorly understood and potentially under-recognized disease among healthcare professionals and veterinarians.

Prevalence and diversity of small rodent-associated Bartonella species in Shangdang Basin, China

The aim of this study was to investigate the occurrence and molecular characteristics of Bartonella infections in small rodents in the Shangdang Basin, China. Small rodents were captured using snap traps, and their liver, spleen, and kidney tissues were harvested for Bartonella detection and identification using a combination of real-time PCR of the ssrA gene (296 bp) and conventional PCR and sequencing of the gltA gene (379 bp). Results showed that 55 of 147 small rodents to be positive for Bartonella, with a positivity rate of 37.41%, and 95% confidence interval of 29.50%- 45.33%. While the positivity rate across genders (42.62% in males and 33.72% in females, χ2 = 1.208, P = 0.272) and tissues (28.57% in liver, 33.59% in spleen, and 36.76% in kidney, χ2 = 2.197, P = 0.333) of small rodents was not statistically different, that in different habitats (5.13% in villages, 84.44% in forests, and 54.17% in farmlands, χ2 = 80.105, P<0.001) was statistically different. There were 42 Bartonella sequences identified in six species, including 30 B. grahamii, three B. phoceensis, two B. japonica, two B. queenslandensis, one B. fuyuanensis and four unknown Bartonella species from Niviventer confucianus, Apodemus agrarius and Tscherskia triton. In addition to habitat, Bartonella species infection could be affected by the rodent species as well. Among the Bartonella species detected in this area, B. grahamii was the dominant epidemic species (accounting for 71.43%). B. grahamii exhibited four distinct clusters, and showed a certain host specificity. In addition, 11 haplotypes of B. grahamii were observed using DNASP 6.12.03, among which nine haplotypes were novel. Overall, high occurrence and genetic diversity of Bartonella were observed among small rodents in the Shangdang Basin; this information could potentially help the prevention and control of rodent-Bartonella species in this area.

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 machadoae sp. nov. isolated from wild rodents in the Pantanal wetland

It has been estimated that 75% of emerging infectious diseases comprise zoonoses, whose majority have free-living animals as reservoirs and are mainly transmitted by arthropod vectors. Although rodents represent important Bartonella reservoirs, there are few studies on the genotypic characterization of Bartonella species commonly found in this taxon and from different Brazilian biomes. Therefore, the present study aimed to investigate the occurrence, isolate and molecularly, morphologically and phenotypically characterize a new Bartonella species infecting free-living rodents sampled in the Brazilian Pantanal, the largest wetland in South America. For this purpose, 129 free-living rodents (79 Thrichomys fosteri, 4 Clyomys laticeps, and Oecomys mamorae) were captured. While blood samples were collected from 57 T. fosteri, 4 C. laticeps and 32 O. mamorae; spleen samples were collected from 22 T. fosteri and 14 O. mamorae. Blood and spleen samples were submitted to a qPCR for Bartonella spp. targeting the nuoG gene, using DNA samples extracted directly from blood/spleen, after passage in pre-enrichment liquid culture, and from colonies obtained from solid culture on chocolate agar. Combining all techniques, occurrence of 24.8% for Bartonella sp. was found among the sampled rodents. One Bartonella isolate (strain 56A) obtained from a T. fosteri's blood sample was closely related to the Bartonella vinsonii complex and selected for Whole Genome Sequencing (WGS) hybrid approach using Illumina NovaSeq and Nanopore sequencing platforms. This strain exhibits a circular 2.7 Mbp genome with an average C+G content of 39% and encoding to 2239 genes. In the phylogenomics based on 291 shared protein-coding genes, this strain was positioned in a unique clade, closely related to Bartonella vinsonii subsp. vinsonii, B. vinsonii subsp. berkhoffii and B. visonii subsp. arupensis. An Average Nucleotide Identity of 85% was found between the obtained isolate and Bartonella species belonging to B. vinsonii complex. These findings supported the separation of this strain, now formally named as Bartonella machadoae sp. nov., from the Bartonella vinsonii complex. In addition, Bartonella machadoae sp. nov. was characterized by capnophilic, microaerophilic and aerobic small rods with absence of pili and flagella. Phylogenetic and distance analyses based on five concatenated molecular markers suggest that Bartonella machadoae may parasite rodents from different Brazilian biomes. In conclusion, we described biochemical, phenotypic and genomic characteristics of Bartonella machadoae nov. sp. isolated from blood samples of T. fosteri rodents from the Brazilian Pantanal.

Detection and genetic diversity of Bartonella species in small mammals from the central region of the Qinghai-Tibetan Plateau, China

In this study, we aimed to investigate the prevalence and molecular characteristics of Bartonella infections in small mammals from the central region of the Qinghai-Tibetan Plateau. Toward this, small mammals were captured using snap traps in Yushu City and Nangqian County, West China, and the spleen tissue was used for Bartonella culture. The suspected positive colonies were evaluated using polymerase chain reaction (PCR) amplification and by sequencing the citrate synthase (gltA) gene. We discovered that 31 out of the 103 small mammals tested positive for Bartonella, with an infection rate of 30.10%. Sex differences between the mammals did not result in a significant difference in infection rate (χ² = 0.018, P = 0.892). However, there was a significant difference in infection rates in different small mammals (Fisher’s exact probability method, P = 0.017) and habitats (χ² = 7.157, P = 0.028). Additionally, 31 Bartonella strains belonging to three species were identified, including B. grahamii (25), B. japonica (4) and B. heixiaziensis (2), among which B. grahamii was the dominant epidemic strain (accounting for 80.65%). Phylogenetic analyses showed that most of the B. grahamii isolates identified in this study may be closely related to the strains isolated from Japan and China. Genetic diversity analyses revealed that B. grahamii strains had high genetic diversity, which showed a certain host and geographical specificity. The results of Tajima’s test suggested that the B. grahamii followed the progressions simulated by a neutral evolutionary model in the process of evolution. Overall, a high prevalence and genetic diversity of Bartonella infection were observed in small mammals in the central region of the Qinghai-Tibetan Plateau. B. grahamii as the dominant epidemic strain may cause diseases in humans, and the corresponding prevention and control measures should be taken into consideration in this area.

Emerging rodent-associated Bartonella: a threat for human health?

Background

Species of the genus Bartonella are facultative intracellular alphaproteobacteria with zoonotic potential. Bartonella infections in humans range from mild with unspecific symptoms to life threatening, and can be transmitted via arthropod vectors or through direct contact with infected hosts, although the latter mode of transmission is rare. Among the small mammals that harbour Bartonella spp., rodents are the most speciose group and harbour the highest diversity of these parasites. Human–rodent interactions are not unlikely as many rodent species live in proximity to humans. However, a surprisingly low number of clinical cases of bartonellosis related to rodent-associated Bartonella spp. have thus far been recorded in humans.

Methods

The main purpose of this review is to determine explanatory factors for this unexpected finding, by taking a closer look at published clinical cases of bartonellosis connected with rodent-associated Bartonella species, some of which have been newly described in recent years. Thus, another focus of this review are these recently proposed species.

Conclusions

Worldwide, only 24 cases of bartonellosis caused by rodent-associated bartonellae have been reported in humans. Possible reasons for this low number of cases in comparison to the high prevalences of Bartonella in small mammal species are (i) a lack of awareness amongst physicians of Bartonella infections in humans in general, and especially those caused by rodent-associated bartonellae; and (ii) a frequent lack of the sophisticated equipment required for the confirmation of Bartonella infections in laboratories that undertake routine diagnostic testing. As regards recently described Bartonella spp., there are presently 14 rodent-associated Candidatus taxa. In contrast to species which have been taxonomically classified, there is no official process for the review of proposed Candidatus species and their names before they are published. This had led to the use of malformed names that are not based on the International Code of Nomenclature of Prokaryotes. Researchers are thus encouraged to propose Candidatus names to the International Committee on Systematics of Prokaryotes for approval before publishing them, and only to propose new species of Bartonella when the relevant datasets allow them to be clearly differentiated from known species and subspecies.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05162-5.

Molecular detection and genetic characterization of small rodents associated Bartonella species in Zhongtiao Mountain, China

The prevalence and molecular characteristics of Bartonella infections in small rodents in the Zhongtiao Mountain, China have been explored. In this study, the liver, spleen and kidney tissues of captured rodents were used for Bartonella spp. detection and identification by combination of real-time PCR of transfer-mRNA (ssrA) gene and traditional PCR and sequencing of citrate synthase (gltA) gene. It was shown that 49.52% of the rodents (52/105) were positive for Bartonella spp.. The infection rate in different gender (χ² = 0.079, P = 0.778) and tissues (χ² = 0.233, P = 0.890) of small rodents did not have statistical difference, but that in different small rodents (Fisher’s exact test, P < 0.001) and habitats (χ² = 5.483, P = 0.019) had statistical difference. And, the sequencing data suggests that Bartonella sequences (n = 31) were identified into three species, including 14 of B. grahamii, 3 of B. queenslandensis and 14 of unknown Bartonella species. Phylogenetic analysis showed that B. grahamii sequences were clustered with the isolates from South Korea and China, and B. queenslandensis sequences were mainly closely related to the isolates from China and Thailand. The genetic diversity analysis showed that B. grahamii and B. queenslandensis sequences exhibited noticeable intraspecies diversity. Taken together our data demonstrates the high prevalence and genetic diversity of Bartonella infections in small rodents in the Zhongtiao Mountain, especially a potential novel Bartonella specie was detected, which could benefit the prevention and control of rodent-Bartonella species in this area.

Laboratory Diagnosis of 37 Cases of Bartonella Endocarditis Based on Enzyme Immunoassay and Real-Time PCR

Bartonella spp., mostly Bartonella quintana and B. henselae, are a common cause of culture-negative endocarditis. Serology using immunofluorescence assay (IFA) and PCR performed on cardiac tissues are the mainstays of diagnosis. We developed an enzyme immunoassay (EIA) and a novel multiplex real-time PCR assay, utilizing Bartonella genus-specific, B. henselae-specific, and B. quintana-specific SimpleProbe probes, for diagnosis of Bartonella endocarditis. We aimed to evaluate the performance of these assays. Thirty-seven patients with definite endocarditis, 18 with B. henselae, 18 with B. quintana, and 1 with B. koehlerae, were studied. Diagnosis was confirmed by conventional PCR and DNA sequencing of surgical cardiac specimens. Similar to the case with IFA, anti-Bartonella IgG titers of ≥1:800 were found in 94% of patients by EIA; cross-reactivity between B. henselae and B. quintana precluded species-specific serodiagnosis, and frequent (41%) but low-titer cross-reactivity between Coxiella burnetii antibodies and B. henselae antigen was found in patients with Q fever endocarditis. Low-titer (1:100) cross-reactivity was uncommonly found also in patients with brucellosis and culture-positive endocarditis, particularly Enterococcus faecalis endocarditis. Real-time PCR performed on explanted heart valves/vegetations was in complete agreement with results of sequence-based diagnosis with characteristic melting curves. The genus-specific probe identified five additional endocarditis-associated Bartonella spp. at the genus level. In conclusion, EIA coupled with a novel real-time PCR assay can play an important role in Bartonella endocarditis diagnosis and expand the diagnostic arsenal at the disposal of the clinical microbiologist. Since serology remains a major diagnostic tool, recognizing its pitfalls is essential to avoid incorrect diagnosis.

Genetic diversity of Bartonella species in small mammals in the Qaidam Basin, western China

Investigation of the prevalence and diversity of Bartonella infections in small mammals in the Qaidam Basin, western China, could provide a scientific basis for the control and prevention of Bartonella infections in humans. Accordingly, in this study, small mammals were captured using snap traps in Wulan County and Ge’ermu City, Qaidam Basin, China. Spleen and brain tissues were collected and cultured to isolate Bartonella strains. The suspected positive colonies were detected with polymerase chain reaction amplification and sequencing of gltA, ftsZ, RNA polymerase beta subunit (rpoB) and ribC genes. Among 101 small mammals, 39 were positive for Bartonella, with the infection rate of 38.61%. The infection rate in different tissues (spleens and brains) (χ² = 0.112, P = 0.738) and gender (χ² = 1.927, P = 0.165) of small mammals did not have statistical difference, but that in different habitats had statistical difference (χ² = 10.361, P = 0.016). Through genetic evolution analysis, 40 Bartonella strains were identified (two different Bartonella species were detected in one small mammal), including B. grahamii (30), B. jaculi (3), B. krasnovii (3) and Candidatus B. gerbillinarum (4), which showed rodent-specific characteristics. B. grahamii was the dominant epidemic strain (accounted for 75.0%). Furthermore, phylogenetic analysis showed that B. grahamii in the Qaidam Basin, might be close to the strains isolated from Japan and China. Overall, we observed a high prevalence of Bartonella infection in small mammals in the Qaidam Basin. B. grahamii may cause human disease, and the pathogenicity of the others Bartonella species needs further study, the corresponding prevention and control measures should be taken into consideration.

Molecular detection of Bartonella in ixodid ticks collected from yaks and plateau pikas (Ochotona curzoniae) in Shiqu County, China

Background

Bartonella bacteria have been associated with an increasingly wide range of human and animal diseases. These emerging pathogens have been identified as being globally dispersed. Ticks and small rodents are known hosts of Bartonella and play a significant role in the preservation and circulation of Bartonella in nature. This study investigated the occurrence of hoist spp. in ticks (Acari: Ixodidae) and plateau pikas (Ochotona curzoniae) in Shiqu County, which is located on the eastern Qinghai-Tibetan Plateau in China. Shiqu County is spread over approximately 26,000 km², with an average altitude of above 4200 m and a vast area of pastureland.

Results

A total of 818 ticks (Dermacentor everestianus, 79.0%, 646/818; Haemaphysalis qinghaiensis, 21.0%, 172/818) were collected from yaks in 4 villages of Shiqu County. Only Bartonella melophagi was detected in tick samples, with a total prevalence of 30.1% (246/818). The infection rates of B. melophagi in ticks from Arizha, Maga, Derongma, and Changxgma were 4.8, 76.8, 12.5, and 18.0%, respectively. The infection rate of B. melophagi in Maga was higher (p < 0.01) than those in other villages. Regarding plateau pikas, the total infection rate of Bartonella spp. was 21.7% (62/286), with 16.7% (12/72), 30.9% (25/81), 13.8% (9/65), and 23.5% (16/68) in Arizha, Maga, Derongma, and Changxgma, respectively. Finally, B. queenslandensis and B. grahamii were detected in plateau pika. No significant difference was observed (p > 0.05) in the infection rates between these study sites.

Conclusion

To date, only D. everestianus and H. qinghaiensis were found in Shiqu County with high infection of Bartonella spp. in the ticks and plateau pika. The threats of Bartonella species to public health should be closely monitored.

Longitudinal Study of Bacterial Infectious Agents in a Community of Small Mammals in New Mexico

Background and Objectives: Vector-borne bacterial diseases represent a substantial public health burden and rodents have been recognized as important reservoir hosts for many zoonotic pathogens. This study investigates bacterial pathogens in a small mammal community of the southwestern United States of America. Methods: A total of 473 samples from 13 wild rodent and 1 lagomorph species were tested for pathogens of public health significance: Bartonella, Brucella, Yersinia, Borrelia, Rickettsia spp., and Anaplasma phagocytophilum. Results: Three animals were positive for Yersinia pestis, and one Sylvilagus audubonii had a novel Borrelia sp. of the relapsing fever group. No Brucella, Rickettsia, or A. phagocytophilum infections were detected. Bartonella prevalence ranged between 0% and 87.5% by animal species, with 74.3% in the predominant Neotoma micropus and 78% in the second most abundant N. albigula. The mean duration of Bartonella bacteremia in mark-recaptured N. micropus and N. albigula was 4.4 months, ranging from <1 to 18 months, and differed among Bartonella genogroups. Phylogenetic analysis of the Bartonella citrate synthase gene (gltA) revealed 9 genogroups and 13 subgroups. Seven genogroups clustered with known or previously reported Bartonella species and strains while two were distant enough to represent new Bartonella species. We report, for the first time, the detection of Bartonella alsatica in North America in Sylvilagus audubonii and expand the known host range of Bartonella washoensis to include Otospermophilus variegatus. Interpretation and Conclusion: This work broadens our knowledge of the hosts and geographic range of bacterial pathogens that could guide future surveillance efforts and improves our understanding of the dynamics of Bartonella infection in wild small mammals.

Bartonella vinsonii subsp. arupensis infection in animals of veterinary importance, ticks and biopsy samples

Testing for vector-borne pathogens in livestock is largely reliant upon blood and tissue. The role of biopsy samples remains poorly explored for detecting tick-borne bacteria in animals. In a 2-year survey, animals of veterinary importance from farms throughout the northern part of Greece were routinely checked for the presence of biopsy samples. Where detected, either a portion or a biopsy was collected together with whole blood samples and any ticks at the site of the biopsy sample. Molecular testing was carried out by real-time PCR targeting the internal transcribed spacer gene of Bartonella species. A total of 68 samples (28 blood samples, 28 biopsy samples and 12 ticks (nine Rhipicephalus bursa and three Rhipicephalus turanicus)) were collected from goats (64 samples) and cattle (four samples). Eight (11.8%) of the 68 samples were positive for Bartonella species. Of the biopsy and whole blood samples, four (14.3%) of each type were positive for Bartonella species. None of the ticks tested positive for Bartonella species. All pairs of positive biopsy samples/whole blood samples originated from the same animals. Positive samples were identified as Bartonella vinsonii subsp. arupensis. Although many more samples from a much wider spectrum of animal species is required before concluding upon the merit of biopsy samples in the study of tick-borne diseases, the significance of our finding warrants further study, both for clinical consequences in small ruminants and for those humans who are farming infected animals.

Fleas of black rats (Rattus rattus) as reservoir host of Bartonella spp. in Chile

Background

Rattus rattus is a widely distributed, invasive species that presents an important role in disease transmission, either directly or through vector arthropods such as fleas. These black rats can transmit a wide variety of pathogens, including bacteria of the genus Bartonella, which can cause diseases in humans and animals. In Chile, no data are available identifying fleas from synanthropic rodents as Bartonella vectors. The aim of this study was to investigate the prevalence of Bartonella spp. in the fleas of R. rattus in areas with different climate conditions and featuring different human population densities.

Methods

In all, 174 fleas collected from 261 R. rattus captured from 30 localities with different human densities (cities, villages, and wild areas) across five hydrographic zones of Chile (hyper-arid, arid, semi-arid, sub-humid, and hyper-humid) were examined. Bartonella spp. presence was determined through polymerase chain reaction, using gltA and rpoB genes, which were concatenated to perform a similarity analysis with BLAST and phylogenetic analysis.

Results

Overall, 15 fleas species were identified; Bartonella gltA and rpoB fragments were detected in 21.2% (37/174) and 19.5% (34/174) of fleas, respectively. A total of 10 of the 15 fleas species found were positive for Bartonella DNA. Leptopsylla segnis was the most commonly collected flea species (n = 55), and it also presented a high prevalence of Bartonella DNA (P% = 34.5%). The highest numbers of fleas of this species were collected in villages of the arid zone. There were no seasonal differences in the prevalence of Bartonella DNA. The presence of Bartonella DNA in fleas was recorded in all hydrographic areas, and the arid zone presented the highest prevalence of this species. Regarding areas with different human densities, the highest prevalence was noted in the villages (34.8% gltA and 31.8% rpoB), followed by cities (14.8% gltA and 11.1% rpoB) and wild areas (7.4% gltA and 14.8% rpoB). The BLAST analysis showed a high similitude (>96%) with four uncharacterized Bartonella genotypes and with two species with zoonotic potential: B. mastomydis and B. tribocorum. The phylogenetic analysis showed a close relationship with B. elizabethae and B. tribocorum. This is the first study to provide evidence of the presence of Bartonella in fleas of R. rattus in Chile, indicating that the villages and arid zone correspond to areas with higher infection risk.

Bartonella quintana and Bartonella vinsonii subsp. vinsonii bloodstream co-infection in a girl from North Carolina, USA

The genus Bartonella consists of globally distributed and highly diverse alpha-proteobacteria that infect a wide-range of mammals. Medically, Bartonella spp. constitute emerging, vector-borne, zoonotic, intravascular organisms that induce long-lasting bacteremia in reservoir-adapted (passive carrier of a microorganism) hosts. At times, these bacteria are accidentally transmitted by animal scratches, bites, needles sticks or vectors to animal or human hosts. We report the first documented human case of blood stream infection with Bartonella vinsonii subsp. vinsonii in a girl from North Carolina, USA, who was co-infected with Bartonella quintana. Limitations of Bartonella spp. serology and the challenges of microbiological culture and molecular diagnostic confirmation of co-infection with more than one Bartonella spp. are discussed. When and where these infections were acquired is unknown; however, exposure to rodents, fleas and cats in the peri-equestrian environment was a suspected source for transmission of both organisms.

Improvement of Bartonella henselae DNA Detection in Cat Blood Samples by Combining Molecular and Culture Methods

Bartonella spp. are bacteria of worldwide distribution that cause asymptomatic to fatal infections in animals and humans. The most common zoonotic species is Bartonella henselae, for which cats are the major natural reservoir host. To better understand Bartonella sp. diagnostic limitations, we determined the frequency of bloodstream infection in 112 cats by comparing and combining the results of multiple conventional and nested PCRs from blood and liquid culture samples. Using liquid culture conventional PCR, Bartonella sp. DNA was amplified from 27.7% of samples (31/112) compared to 90.2% of samples (101/112) by combining nested PCR from blood and liquid culture, indicating that PCR testing of more than one type of sample provides better sensitivity than a standalone PCR and that bloodstream infection is very frequent among cats in southeastern Brazil. This study reinforces the need for multistep testing for Bartonella sp. infection to prevent false-negative diagnostic results, even in reservoir hosts such as cats that typically maintain higher bacteremia levels.

Bartonella Species, an Emerging Cause of Blood-Culture-Negative Endocarditis

Since the reclassification of the genus Bartonella in 1993, the number of species has grown from 1 to 45 currently designated members. Likewise, the association of different Bartonella species with human disease continues to grow, as does the range of clinical presentations associated with these bacteria. Among these, blood-culture-negative endocarditis stands out as a common, often undiagnosed, clinical presentation of infection with several different Bartonella species. The limitations of laboratory tests resulting in this underdiagnosis of Bartonella endocarditis are discussed. The varied clinical picture of Bartonella infection and a review of clinical aspects of endocarditis caused by Bartonella are presented. We also summarize the current knowledge of the molecular basis of Bartonella pathogenesis, focusing on surface adhesins in the two Bartonella species that most commonly cause endocarditis, B. henselae and B. quintana. We discuss evidence that surface adhesins are important factors for autoaggregation and biofilm formation by Bartonella species. Finally, we propose that biofilm formation is a critical step in the formation of vegetative masses during Bartonella-mediated endocarditis and represents a potential reservoir for persistence by these bacteria.

Liver microbiome of Peromyscus leucopus, a key reservoir host species for emerging infectious diseases in North America

Microbiome studies generally focus on the gut microbiome, which is composed of a large proportion of commensal bacteria. Here we propose a first analysis of the liver microbiome using next generation sequencing as a tool to detect potentially pathogenic strains. We used Peromyscus leucopus, the main reservoir host species of Lyme disease in eastern North America, as a model and sequenced V5-V6 regions of the 16S gene from 18 populations in southern Quebec (Canada). The Lactobacillus genus was found to dominate the liver microbiome. We also detected a large proportion of individuals infected by Bartonella vinsonii arupensis, a human pathogenic bacteria responsible for endocarditis, as well as Borrelia burgdorferi, the pathogen responsible for Lyme disease in North America. We then compared the microbiomes among two P. leucopus genetic clusters occurring on either side of the St. Lawrence River, and did not detect any effect of the host genotype on their liver microbiome assemblage. Finally, we report, for the first time, the presence of B. burgdorferi in a small mammal host from the northern side of the St. Lawrence River, in support of models that have predicted the northern spread of Lyme disease in Canada.

Zoonotic pathogens in Atlantic Forest wild rodents in Brazil: Bartonella and Coxiella infections

Zoonotic pathogens comprise a significant and increasing fraction of all emerging and re-emerging infectious diseases that plague humans. Identifying host species is one of the keys to controlling emerging infectious diseases. From March 2007 until April 2012, we collected a total of 131 wild rodents in eight municipalities of Rio de Janeiro, Brazil. We investigated these rodents for infection with Coxiella burnetii, Bartonella spp. and Rickettsia spp. In total, 22.1% (29/131) of the rodents were infected by at least one pathogen; co-infection was detected in 1.5% (2/131) of rodents. Coxiella burnetii was detected in 4.6% (6/131) of the wild animals, 17.6% of the rodents harbored Bartonella spp. No cases of Rickettsia were identified. Bartonella doshiae and Bartonella vinsonii were the species found on the wild mammals. This report is the first to note C. burnetii, B. doshiae and B. vinsonii natural infections in Atlantic Forest wild rodents in Brazil. Our work highlights the potential risk of transmission to humans, since most of the infected specimens belong to generalist species that live near human dwellings.

Bartonella Endocarditis and Pauci-Immune Glomerulonephritis: A Case Report and Review of the Literature

Among culture-negative endocarditis in the United States, Bartonella species are the most common cause, with Bartonella henselae and Bartonella quintana comprising the majority of cases. Kidney manifestations, particularly glomerulonephritis, are common sequelae of infectious endocarditis, with nearly half of all Bartonella patients demonstrating renal involvement. Although a pauci-immune pattern is a frequent finding in infectious endocarditis-associated glomerulonephritis, it is rarely reported in Bartonella endocarditis. Anti-neutrophil cytoplasmic antibody (ANCA) positivity can be seen with many pathogens causing endocarditis and has been previously reported with Bartonella species. In addition, ANCA-associated vasculitis can also present with renal and cardiac involvement, including noninfectious valvular vegetations and pauci-immune glomerulonephritis. Given the overlap in their clinical presentation, it is difficult to differentiate between Bartonella endocarditis and ANCA-associated vasculitis but imperative to do so to guide management decisions. We present a case of ANCA-positive Bartonella endocarditis with associated pauci-immune glomerulonephritis that was successfully treated with medical management alone.

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.

Molecular epidemiology ofBartonellaspecies isolated from ground squirrels and other rodents in northern California

Bartonellaspp. are endemic in wild rodents in many parts of the world. A study conducted in two northern California counties (Sonoma and Yolo) sampling California ground squirrels (Otospermophilus beecheyi) and four other rodent species (Peromyscus maniculatus, P. boylii, P. trueiandNeotoma fuscipes) led to the isolation of small Gram-negative bacilli which were identified asBartonellaspp. based on colony morphology, polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) and partial gene sequencing. Overall,Bartonellaspp. were isolated from the blood of 71% (32/45) of the ground squirrels and one third (22/66) of the other rodents. PCR–RFLP analysis of thegltA and 16S rRNA genes yielded seven unique profiles, four for the ground squirrels and three for the other rodents. Isolates from each PCR–RFLP profiles were submitted for partial sequencing. Ground squirrel isolates were most closely related toB. washoensis, whereas the other rodent isolates were closest toB. vinsoniisubsp.vinsoniiandB. vinsoniisubsp.arupensis. Two of these three species or subspecies are known zoonotic agents.

PREVALENCE AND DIVERSITY OF BARTONELLA SPECIES IN WILD SMALL MAMMALS IN ASIA

We collected 641 small mammals belonging to 17 species of Rodentia and four species of Soricomorpha in Japan, Korea, Russia, Taiwan, and Thailand and investigated the prevalence and genetic diversity of Bartonella species. Apodemus (field mice) and Rattus (rats) were the most-common genera captured, making up 56.0% and 23.1% of the total specimens, respectively. Bartonellae were isolated from 54.6% of the collected animals, and the prevalence varied depending on the host species and the country of origin. The isolates were identified to the species level based on gltA and rpoB sequences. Although most Bartonella species were shared by more than two host species, the distribution patterns of Bartonella species clearly differed among the four most-common host genera: Apodemus, Rattus, Myodes (voles), and Suncus (shrews). The predominant Bartonella species were Bartonella grahamii in Apodemus, Bartonella tribocorum in Rattus, B. grahamii and Bartonella taylorii in Myodes, and an unclassified Bartonella sp. in Suncus.

Bats as reservoir hosts of human bacterial pathogen, Bartonella mayotimonensis

A plethora of pathogenic viruses colonize bats. However, bat bacterial flora and its zoonotic threat remain ill defined. In a study initially conducted as a quantitative metagenomic analysis of the fecal bacterial flora of the Daubenton's bat in Finland, we unexpectedly detected DNA of several hemotrophic and ectoparasite-transmitted bacterial genera, including Bartonella. Bartonella spp. also were either detected or isolated from the peripheral blood of Daubenton's, northern, and whiskered bats and were detected in the ectoparasites of Daubenton's, northern, and Brandt's bats. The blood isolates belong to the Candidatus-status species B. mayotimonensis, a recently identified etiologic agent of endocarditis in humans, and a new Bartonella species (B. naantaliensis sp. nov.). Phylogenetic analysis of bat-colonizing Bartonella spp. throughout the world demonstrates a distinct B. mayotimonensis cluster in the Northern Hemisphere. The findings of this field study highlight bats as potent reservoirs of human bacterial pathogens.

Bartonella infection in rodents and their flea ectoparasites: an overview

Epidemiological studies worldwide have reported a high prevalence and a great diversity of Bartonella species, both in rodents and their flea parasites. The interaction among Bartonella, wild rodents, and fleas reflects a high degree of adaptation among these organisms. Vertical and horizontal efficient Bartonella transmission pathways within flea communities and from fleas to rodents have been documented in competence studies, suggesting that fleas are key players in the transmission of Bartonella to rodents. Exploration of the ecological traits of rodents and their fleas may shed light on the mechanisms used by bartonellae to become established in these organisms. The present review explores the interrelations within the Bartonella-rodent-flea system. The role of the latter two components is emphasized.

Bartonella, a common cause of endocarditis: a report on 106 cases and review

Bartonella spp. are fastidious bacteria that cause blood culture-negative endocarditis and have been increasingly reported. In this study, we included all patients retrospectively and prospectively diagnosed with Bartonella endocarditis in our French reference center between 2005 and 2013. Our diagnosis was based on the modified Duke criteria and microbiological findings, including serological and PCR results. To review the published literature, we searched all human Bartonella endocarditis cases published in the PubMed database between January 2005 and October 2013. We report here a large series of 106 cases, which include 59 cases that had not previously been reported or mentioned. Indirect immunofluorescence assays, Western blotting, and real-time PCR from total blood, serum, and valve tissue exhibited sensitivities of 58%, 100%, 33%, 36%, and 91%, respectively. The number of cases reported in the literature between 2005 and 2013 increased to reach a cumulative number of 196 cases. The number of cases reported in the literature by other centers is increasing more rapidly than that reported by our French reference center (P < 10(-2)). Currently, there is a lack of criteria for the diagnosis of Bartonella endocarditis. We suggest that a positive PCR result from a cardiac valve or blood specimen, an IgG titer of ≥800 using an immunofluorescence assay, or a positive Western blot assay be considered major Duke criteria for Bartonella endocarditis. There is no real increase in the incidence of these infections but rather a better understanding and interest in the disease resulting from the improvement of diagnostic tools.

Koch's postulates and the pathogenesis of comparative infectious disease causation associated with Bartonella species

In his homage to Lucretius (‘Georgica’), Vergil is credited with stating: ‘Felix qui potuit rerum cognoscere causas’ (‘Fortunate is he who knows the causes of things’). Based on numerous commentaries and publications it is obvious that clinicians, diagnosticians and biomedical research scientists continue to struggle with disease causation, particularly in the assessment of the pathogenic role of ‘stealth pathogens’ that produce persistent infections in the host. Bartonella species, because of their evolutionary ability to induce persistent intravascular infections, present substantial challenges for researchers attempting to clarify the ability of these stealth bacteria to cause disease. By studying the comparative biological and pathological behaviour of microbes across mammalian genera, researchers might be able more rapidly to advance medical science and, subsequently, patient care by undertaking focused research efforts involving a single mammalian species or by attempting to recapitulate a complex disease in an rodent model. Therefore, in an effort to further assist in the establishment of disease causation by stealth pathogens, we use recent research observations involving the genus Bartonella to propose an additional postulate of comparative infectious disease causation to Koch's postulates.

Detection of Bartonella spp. DNA in clinical specimens using an internally controlled real-time PCR assay

Bartonella henselae is the causative agent of cat-scratch disease (CSD), usually presenting itself as a -self-limiting lymphadenopathy. In this chapter an internally controlled Taqman probe-based real-time PCR targeting the groEL gene of Bartonella spp. is described. This assay allows for the rapid, sensitive, and simple detection of Bartonella spp. in samples from CSD or endocarditis suspects, and it is suitable for implementation in the diagnostic microbiology laboratory.

Recombination, diversity and allele sharing of infectivity proteins between Bartonella species from rodents

The alpha-Proteobacterium Bartonella is a common parasite of voles and mice, giving rise to short-lived (4 weeks to 2 months) infections. Here, we report high sequence diversity in genes of the VirB/VirD type IV secretion system (T4SS), amongst Bartonella from natural rodent populations in NE Poland. The VirB5 protein is predicted to consist of three conserved alpha helices separated by loops of variable length which include numerous indels. The C-terminal domain includes repeat stretches of KEK residues, reflecting underlying homopolymeric stretches of adenine residues. A total of 16 variants of VirB5, associated with host identity, but not bacterial taxon, were identified from 22 Bartonella isolates. One was clearly a recombinant from two others, another included an insertion of two KEK repeats. The virB5 gene appears to evolve via both mutation and recombination, as well as slippage mediated insertion/deletion events. The recombinational units are thought to be relatively short, as there was no evidence of linkage disequilibrium between virB5 and the bepA locus only 5.5 kb distant. The diversity of virB5 is assumed to be related to immunological role of this protein in Bartonella infections; diversity of virB5 may assist persistence of Bartonella in the rodent population, despite the relatively short (3-4 weeks) duration of individual infections. It is clear from the distribution of virB5 and bepA alleles that recombination within and between clades is widespread, and frequently crosses the boundaries of conventionally recognised Bartonella species.

Bartonella vinsonii subsp. arupensis in humans, Thailand

We identified Bartonella vinsonii subsp. arupensis in pre-enriched blood of 4 patients from Thailand. Nucleotide sequences for transfer-messenger RNA gene, citrate synthase gene, and the 16S-23S rRNA internal transcribed spacer were identical or closely related to those for the strain that has been considered pathogenic since initially isolated from a human in Wyoming, USA.

Bartonella vinsonii endocarditis in an adolescent with congenital heart disease

We report the second human case of Bartonella vinsonii subsp. berkhoffii endocarditis in a 19-year-old male with congenital heart disease. Diagnosis was established by Bartonella antibodies detected by immunofluorescence, and polymerase chain reaction amplification and sequencing from blood.

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.

Persistent infection or successive reinfection of deer mice with Bartonella vinsonii subsp. arupensis

Bartonella infections are common in rodents. From 1994 to 2006, longitudinal studies of a rodent community, consisting mainly of deer mice (Peromyscus maniculatus), were conducted in southwestern Colorado to study hantaviruses. Blood samples from deer mice captured one or more times during the period 2003 to 2006 (n = 737) were selected to study bartonellae in deer mice. Bartonellae were found to be widely distributed in that population, with an overall prevalence of 82.4% (607/737 mice). No correlation was found between bartonella prevalence and deer mouse weight or sex. Persistent or successive infections with bartonellae were observed in deer mice captured repeatedly, with a prevalence of 83.9% (297/354), and the infection appeared to last for more than 1 year in some of them. Persistent infection with bartonellae may explain the high prevalence of these bacteria in deer mice at this site and, perhaps, elsewhere. Genetic analysis demonstrated that deer mouse-borne bartonella isolates at this site belong to the same species, B. vinsonii subsp. arupensis, demonstrating a specific relationship between B. vinsonii subsp. arupensis and deer mice.

Recombination within and between species of the alpha proteobacterium Bartonella infecting rodents

Bartonella infections from wild mice and voles (Apodemus flavicollis, Mi. oeconomus, Microtus arvalis and Myodes glareolus) were sampled from a forest and old-field habitats of eastern Poland; a complex network of Bartonella isolates, referrable to B. taylorii, B. grahamii, B. birtlesii and B. doshiae, was identified by the sequencing of a gltA fragment, comparable to previous studies of Bartonella diversity in rodents. Nested clade analysis showed that isolates could be assigned to zero- and one-step clades which correlated with host identity and were probably the result of clonal expansion; however, sequencing of other housekeeping genes (rpoB, ribC, ftsZ, groEl) and the 16S RNA gene revealed a more complex situation with clear evidence of numerous recombinant events in which one or both Bartonella parents could be identified. Recombination within gltA was found to have generated two distinct variant clades, one a hybrid between B. taylorii and B. doshiae, the other between B. taylorii and B. grahamii. These recombinant events characterised the differences between the two-step and higher clades within the total nested cladogram, involved all four species of Bartonella identified in this work and appear to have played a dominant role in the evolution of Bartonella diversity. It is clear, therefore, that housekeeping gene phylogenies are not robust indicators of Bartonella diversity, especially when only a single gene (gltA or 16S RNA) is used. Bartonella clades infecting Microtus were most frequently involved in recombination and were most frequently tip clades within the cladogram. The role of Microtus in influencing the frequency of Bartonella recombination remains unknown.

Bartonella species in small mammals and their ectoparasites in Taiwan

Bartonella spp. prevalence in small mammals and their ectoparasites was investigated in Taiwan. Blood samples were obtained from 66 rats, 20 shrews, 276 mites (Laelaps spp.), 74 fleas (Xenopsylla cheopis), 81 lice (Polyplax spp.), and 47 ticks (41 Dermacentor spp. and 6 Ixodes spp.). Bartonellae were isolated or detected in 27 (31.4%) animals. Bartonella DNA was detected in 48 (64.9%) fleas and 11 (64.7%) pooled lice samples, but not in mite and tick samples. Bartonella phoceensis, B. queenslandensis, B. tribocorum, B. elizabethae, and B. rattimassiliensis were isolated or detected in bacteremic mammals. For the first time in Taiwan, B. tribocorum, B. elizabethae, B. queenslandensis, and a B. rochalimae-like strain were detected in fleas, and B. tribocorum, B. phoceensis, and B. rattimassiliensis were detected in lice obtained from small mammals. A broader range of Bartonella species was identified in the ectoparasites than in the small mammals.

Variability of Bartonella genotypes among small mammals in Spain

In order to study which Bartonella genotypes are circulating among small mammals in Spain, we analyzed the spleens of 395 animals from three different areas-247 animals from the Basque Country (northern Spain), 121 animals from Catalonia (northeastern Spain), and 27 animals from Madrid (central Spain)-by a triplex PCR combined with a reverse line blot previously described by our group. The prevalence of Bartonella was 26.8% (106/395), and in 4.8% (19/395) of the animals more than one Bartonella genotype was detected. The study of gltA and the intergenic transcribed spacer in the positive samples demonstrated a large diversity, allowing the assignation of them into 22 genotypes. The most prevalent genotypes were 2 and 3, which are closely related to Bartonella taylorii. In addition, nine genotypes were associated with specific mammal species. Genotypes close to the zoonotic Bartonella grahamii, Bartonella elizabethae, and Bartonella rochalimae were also detected. Ten genotypes showed a percentage of similarity with known Bartonella species lower than 96%, suggesting the presence of potential new species. Further studies of the impact of these pathogens on human health and especially in cases of febrile illness in Spain are strongly recommended. Furthermore, our method has been updated with 21 new probes in a final panel of 36, which represents a robust molecular tool for clinical and environmental Bartonella studies.

Human isolates of Bartonella tamiae induce pathology in experimentally inoculated immunocompetent mice

Background

Bartonella tamiae, a newly described bacterial species, was isolated from the blood of three hospitalized patients in Thailand. These patients presented with headache, myalgia, anemia, and mild liver function abnormalities. Since B. tamiae was presumed to be the cause of their illness, these isolates were inoculated into immunocompetent mice to determine their relative pathogenicity in inducing manifestations of disease and pathology similar to that observed in humans.

Methods

Three groups of four Swiss Webster female mice aged 15-18 months were each inoculated with 10^6-7 colony forming units of one of three B. tamiae isolates [Th239, Th307, and Th339]. A mouse from each experimental group was sampled at 3, 4, 5 and 6 weeks post-inoculation. Two saline inoculated age-matched controls were included in the study. Samples collected at necropsy were evaluated for the presence of B. tamiae DNA, and tissues were formalin-fixed, stained with hematoxylin and eosin, and examined for histopathology.

Results

Following inoculation with B. tamiae, mice developed ulcerative skin lesions and subcutaneous masses on the lateral thorax, as well as axillary and inguinal lymphadenopathy. B. tamiae DNA was found in subcutaneous masses, lymph node, and liver of inoculated mice. Histopathological changes were observed in tissues of inoculated mice, and severity of lesions correlated with the isolate inoculated, with the most severe pathology induced by B. tamiae Th239. Mice inoculated with Th239 and Th339 demonstrated myocarditis, lymphadenitis with associated vascular necrosis, and granulomatous hepatitis and nephritis with associated hepatocellular and renal necrosis. Mice inoculated with Th307 developed a deep dermatitis and granulomas within the kidneys.

Conclusions

The three isolates of B. tamiae evaluated in this study induce disease in immunocompetent Swiss Webster mice up to 6 weeks after inoculation. The human patients from whom these isolates were obtained had clinical presentations consistent with the multi-organ pathology observed in mice in this study. This mouse model for B. tamiae induced disease not only strengthens the causal link between this pathogen and clinical illness in humans, but provides a model to further study the pathological processes induced by these bacteria.

Identification of Bartonella infections in febrile human patients from Thailand and their potential animal reservoirs

To determine the role of Bartonella species as causes of acute febrile illness in humans from Thailand, we used a novel strategy of co-cultivation of blood with eukaryotic cells and subsequent phylogenetic analysis of Bartonella-specific DNA products. Bartonella species were identified in 14 blood clots from febrile patients. Sequence analysis showed that more than one-half of the genotypes identified in human patients were similar or identical to homologous sequences identified in rodents from Asia and were closely related to B. elizabethae, B. rattimassiliensis, and B. tribocorum. The remaining genotypes belonged to B. henselae, B. vinsonii, and B. tamiae. Among the positive febrile patients, animal exposure was common: 36% reported owning either dogs or cats and 71% reported rat exposure during the 2 weeks before illness onset. The findings suggest that rodents are likely reservoirs for a substantial portion of cases of human Bartonella infections in Thailand.

Enrichment culture and molecular identification of diverse Bartonella species in stray dogs

Using pre-enrichment culture in Bartonella alpha-Proteobacteria growth medium (BAPGM) followed by PCR amplification and DNA sequence identification that targeted a fragment of the citrate synthase gene (gltA), we provide evidence of common bartonella infections and diverse Bartonella species in the blood of stray dogs from Bangkok and Khon Kaen, Thailand. The overall prevalence of all Bartonella species was 31.3% (60/192), with 27.9% (31/111) and 35.8% (29/81) in the stray dogs from Bangkok and Khon Kaen, respectively. Phylogenetic analyzes of gltA identified eight species/genotypes of Bartonella in the blood of stray dogs, including B. vinsonii subsp. arupensis, B. elizabethae, B. grahamii, B. quintana, B. taylorii, and three novel genotypes (BK1, KK1 and KK2) possibly representing unique species with ≤ 90.2% similarities to any of the known Bartonella species B. vinsonii subsp. arupensis was the only species detected in dogs from both sites, B. quintana and BK1 were found in the dogs from Bangkok, B. elizabethae, B. taylorii, KK1 and KK2 were found in the dogs from Khon Kaen. We conclude that stray dogs in Thailand are frequently infected with Bartonella species that vary with geographic region. As some Bartonella species detected in the present study are considered pathogenic for humans, stray dogs in Thailand may serve as possible reservoirs for Bartonella causing human illnesses. Further work is needed to determine the role of those newly discovered Bartonella genotypes/species in human and veterinary medicine.

Genome dynamics of Bartonella grahamii in micro-populations of woodland rodents

Background

Rodents represent a high-risk reservoir for the emergence of new human pathogens. The recent completion of the 2.3 Mb genome of Bartonella grahamii, one of the most prevalent blood-borne bacteria in wild rodents, revealed a higher abundance of genes for host-cell interaction systems than in the genomes of closely related human pathogens. The sequence variability within the global B. grahamii population was recently investigated by multi locus sequence typing, but no study on the variability of putative host-cell interaction systems has been performed.

Results

To study the population dynamics of B. grahamii, we analyzed the genomic diversity on a whole-genome scale of 27 B. grahamii strains isolated from four different species of wild rodents in three geographic locations separated by less than 30 km. Even using highly variable spacer regions, only 3 sequence types were identified. This low sequence diversity contrasted with a high variability in genome content. Microarray comparative genome hybridizations identified genes for outer surface proteins, including a repeated region containing the fha gene for filamentous hemaggluttinin and a plasmid that encodes a type IV secretion system, as the most variable. The estimated generation times in liquid culture medium for a subset of strains ranged from 5 to 22 hours, but did not correlate with sequence type or presence/absence patterns of the fha gene or the plasmid.

Conclusion

Our study has revealed a geographic microstructure of B. grahamii in wild rodents. Despite near-identity in nucleotide sequence, major differences were observed in gene presence/absence patterns that did not segregate with host species. This suggests that genetically similar strains can infect a range of different hosts.