Sneaky tactics: Ingenious immune evasion mechanisms of Bartonella.

Gram-negative Bartonella species are facultative intracellular bacteria that can survive in the harsh intracellular milieu of host cells. They have evolved strategies to evade detection and degradation by the host immune system, which ensures their proliferation in the host. Following infection, Bartonella alters the initial immunogenic surface-exposed proteins to evade immune recognition via antigen or phase variation. The diverse lipopolysaccharide structures of certain Bartonella species allow them to escape recognition by the host pattern recognition receptors. Additionally, the survival of mature erythrocytes and their resistance to lysosomal fusion further complicate the immune clearance of this species. Certain Bartonella species also evade immune attacks by producing biofilms and anti-inflammatory cytokines and decreasing endothelial cell apoptosis. Overall, these factors create a challenging landscape for the host immune system to rapidly and effectively eradicate the Bartonella species, thereby facilitating the persistence of Bartonella infections and creating a substantial obstacle for therapeutic interventions. This review focuses on the effects of three human-specific Bartonella species, particularly their mechanisms of host invasion and immune escape, to gain new perspectives in the development of effective diagnostic tools, prophylactic measures, and treatment options for Bartonella infections.

Epidemiology of Bartonella henselae infection in pet and stray cats in Croatia with risk factors analysis.

BACKGROUND: Cats are the primary reservoirs of the bacterium Bartonella henselae, the main cause of cat-scratch disease in humans. The main vector of the bacterium is the cat flea, Ctenocephalides felis. In southeastern Europe, data are lacking on the prevalence of B. henselae infection in cats, the strains of B. henselae involved and the risk factors associated with the infection. METHODS: Blood samples collected in ethylenediaminetetraacetic acid-containing tubes from 189 domestic cats (156 pet cats and 33 stray cats) from Zagreb, the capital city of Croatia, and 10 counties throughout Croatia were cultured for Bartonella spp. Following culture, bacterial isolates were genotyped at eight loci after using PCR to amplify 16S ribosomal RNA (rRNA) and the internal transcribed spacer region between the 16S and 23S rRNA sequences. Univariate and multivariate logistic regression were used to identify risk factors for B. henselae infection in cats. RESULTS: Bartonella spp. was detected in 31 cats (16.4%), and subsequent genotyping at the eight loci revealed B. henselae in all cases. Thirty complete multilocus sequence typing profiles were obtained, and the strains were identified as four sequence types that had been previously reported, namely ST5 (56.7%), ST6 (23.3%), ST1 (13.3%) and ST24 (3.3%), as well as a novel sequence type, ST33 (3.3%). The univariate analysis revealed a significantly higher risk of B. henselae infection in cats residing in coastal areas of Croatia (odds ratio [OR] 2.592, 95% confidence interval [CI] 1.150-5.838; P = 0.0191) and in cats with intestinal parasites (OR 3.207, 95% CI 1.088-9.457; P = 0.0279); a significantly lower risk was identified in cats aged > 1 year (OR 0.356, 95% CI 0.161-0.787; P = 0.0247) and in cats sampled between April and September (OR 0.325, 95% CI 0.147-0.715; P = 0.005). The multivariate analysis that controlled for age showed a positive association with the presence of intestinal parasites (OR 4.241, 95% CI 1.243-14.470; P = 0.0119) and coastal residence (OR 2.567, 95% CI 1.114-5.915; P = 0.0216) implying increased risk of infection, and a negative association with sampling between April and September (OR 0.379, 95% CI 0.169-0.848; P = 0.018) implying a decreased risk of infection. After controlling for the season, an increased risk of infection remained for the coastal region (OR 2.725, 95% CI 1.200-6.186; P = 0.012). CONCLUSIONS: Bartonella henselae is prevalent throughout Croatia and is a public health threat. Environmental and host factors can significantly affect the risk of infection, and these should be explored in more detail. The presence of intestinal parasites highlights the need to eliminate the flea vector, Ctenocephalides felis, as the most effective approach to control infections in cats and humans.

A comparison of Bartonella henselae infection in immunocompetent and immunocompromised mice.

Bartonellosis refers to disease caused by the Bartonella genus of bacteria. The breadth of disease manifestations associated with Bartonella is currently expanding and includes regional lymphadenopathy, rheumatic, ocular, and neurological disorders. The dearth of knowledge regarding diagnosis, treatment and pathogenesis of this disease can be partially attributed to the lack of a reliable small animal model for the disease. For this study, Bartonella henselae, the most common species associated with human disease, was injected into Swiss Webster (SW) mice. When the outcome indicated that productive infection did not occur, SCID/Beige (immune compromised) mice were inoculated. While SW mice may potentially harbor an acute infection, less than 10 days in length, the SCID/Beige model provided a sustained infection lasting up to 30-days. These data indicate that SCID/Beige mice can provide a model to study Bartonella infection, therapeutics, and vector dynamics in the future.

Genetic diversity of Bartonella rpoB haplotypes in domestic cats from Chile.

The study aimed to determine the inter and intra-host Bartonella spp. genetic diversity in cats from Chile. 'Seventy-nine cats' blood DNA samples qPCR Bartonella spp. positive were subjected to T-A cloning of Bartonella spp. rpoB partial gene (825 bp), and sequencing by Sanger method. The sequences were submitted to phylogenetic and polymorphism analysis. Thirty-six (45.6%) samples were successfully cloned, generating 118 clones of which 109 showed 99.6%-100% identity with Bartonella henselae whereas 9 showed 99.8-100% identity with Bartonella koehlerae. Haplotype analysis yielded 29 different rpoB-B. henselae haplotypes, one (hap#2) overrepresented in 31 out of 33 cats, and 4 rpoB-B. koehlerae haplotypes, with hap#2 represented in all 3 B. koehlerae infected cats. More than one rpoB -B. henselae and B. koehlerae haplotypes were identified in individual cats, reporting by first time coinfection by different B. henselae/B. koehlerae rpoB variants in cats from Chile.

Zoonotic bacterial pathogens in bats samples around the world: a scoping review.

The aim of this scoping review was to describe the zoonotic bacterial pathogens already reported and their frequency in different bat species. Six databases were searched, without restriction on the year or location where the studies were carried out. Based on the inclusion and exclusion criteria, 146 studies that were published between 1964 and 2020 (most after 2005) were selected. In these studies, 102 zoonotic bacterial genera were described in different samples of fourteen bat families in 55 countries, suggesting the possible role of bats as hosts for these pathogens. The pathogens mainly identified in bats were Bartonella spp., Leptospira spp. and Staphylococcus spp. In conclusion, the information provided by this scoping review expands the knowledge about zoonotic bacterial pathogens already identified in bats, which can guide epidemiological surveillance policies for these pathogens in different countries.

Molecular detection and characterization of Bartonella spp. in small mammals in the Amazonia and Cerrado biomes, midwestern Brazil.

Although Bartonella spp. have been worldwide described in rodents and bats, few studies have reported these agents in marsupials. The present work aimed to investigate the occurrence and genetic diversity of Bartonella in small mammals (rodents, marsupials, and bats) and associated ectoparasites in two ecoregions (Amazonia and Cerrado biomes) in midwestern Brazil. For this purpose, DNA samples from 378 specimens of small mammals (128 rodents, 111 marsupials, and 139 bats) and 41 fleas (Siphonaptera) were screened for the Bartonella genus employing a quantitative real-time PCR assay (qPCR) based on the nuoG (nicotinamide adenine dinucleotide dehydrogenase gamma subunit) gene. Then, positive samples in qPCR were submitted to conventional PCR (cPCR) assays targeting the gltA, ftsZ, and rpoB genes. One (0.78 %) rodent, 23 (16.54 %) bats, and 3 (7.31 %) fleas showed positive results in the qPCR for Bartonella sp. After cPCR amplification and sequencing, 13 partial Bartonella DNA sequences of the following genes were obtained only from bats´ blood samples: 9 gltA (citrate synthase), 3 ftsZ (cell division protein), and 1 rpoB (RNA polymerase beta subunit). The maximum likelihood inference based on the gltA gene positioned the obtained sequences in three different clades, closely related to Bartonella genotypes previously detected in other bat species and bat flies sampled in Brazil and other countries from Latin America. Similarly, the ftsZ sequences clustered in two different clades with sequences described in bats from Brazil, other countries from Latin America, and Georgia (eastern Europe). Finally, the Bartonella rpoB from a specimen of Lophostoma silvicolum clustered with a Bartonella sp. sequence obtained from a Noctilio albiventris (KP715475) from French Guiana. The present study provided valuable insights into the diversity of Bartonella genotypes infecting bats from two ecoregions (Amazonia and Cerrado) in midwestern Brazil and emphasized that further studies should be conducted regarding the description and evaluation of different lineages of Bartonella in wild small mammals and their ectoparasites in different Brazilian biomes.

Detection of Bartonella bovis DNA in blood samples from a veterinarian in Mexico.

The genus Bartonella encompasses 38 validated species of Gram-negative, facultative intracellular bacteria that colonize the endothelial cells and erythrocytes of a wide spectrum of mammals. To date, 12 Bartonella species have been recorded infecting humans, causing diseases of long historical characterization, such as cat scratch fever and trench fever, and emerging bartonellosis that mainly affect animal health professionals. For this reason, this study aimed to report a documented case of Bartonella bovis infecting a veterinarian from Mexico by the amplification, sequencing and phylogenetic reconstruction of the citrate synthase (gltA) and the RNA polymerase beta-subunit (rpoB) genes, and to report the natural course of this infection. To our knowledge, this work is the first to report the transmission of B. bovis via needlestick transmission to animal health workers in Latin America.

Bartonella henselae as a putative trigger for chronic type 2 leprosy reactions.

Leprosy reactions are an acute inflammatory phenomenon that can arise before diagnosis, during treatment, or after cure of leprosy. These reactions are considered one of the main diseases that cause physical disabilities. Immunosuppressive treatment for these immune responses makes these patients susceptible to coinfections, which can trigger new leprosy reactions. The main objective of this study was to evaluate the occurrence of infection by Bartonella sp. in blood samples from 47 patients who had untreatable episodes of type 2 leprosy reactions for more than six months, comparing them with a control group. Cultures and molecular methods (PCR) were used. Amplicons from species-specific reactions and sequencing showed a higher prevalence of Bartonella henselae infection in patients, 19/47 (40.4 %), compared to control, 9/50 (18.0 %), p = 0.0149. Five patients accepted treatment for coinfection, and all showed improvement in leprosy reactions with treatment for B. henselae infection. We conclude that these bacteria can trigger chronic reactions of type 2 leprosy and should be investigated in these patients. SUMMARY LINE: Patients who have chronic type 2 leprosy reactions are more susceptible to Bartonella henselae infection than controls: 19/47 (40.4 %) compared 9/50 (18.0 %), p = 0.0149.

Genetic characterization of Bartonella henselae samples isolated from stray cats by multi-locus sequence typing.

BACKGROUND: Bartonella henselae is one of the most commonly identified Bartonella species associated with several human diseases. Although B. henselae was detected in humans and cats in Turkey, they have not been genotyped previously. Therefore, this study aimed to genotype B. henselae samples (n = 44) isolated from stray cats using the multi-locus sequence typing (MLST) method. For this aim, eight different housekeeping markers were amplified by nested PCR and then sequenced to reveal sequence types (STs) of B. henselae samples. RESULTS: Allelic profiles obtained from 40 B. henselae isolates (90.9%) were compatible with available allelic profiles in the MLST online database. However, allelic profiles obtained from the remaining 4 B. henselae isolates (9.1%) were incompatible with the database. Among B. henselae isolates with compatible allelic profiles, 5 different STs including ST1, ST5, ST9, ST35 and ST36 were identified according to the B. henselae MLST online database. ST35 was the most prevalent ST with a prevalence rate of 29.5% (13/44), followed by ST36 with a prevalence rate of 22.7% (10/44). In addition, ST5 (16%, 7/44) and ST9 (18.2%, 8/44) were also among the prevalent STs. The prevalence of ST1 was 4.5% (2/44). For B. henselae isolates with incompatible allelic profiles, we recommended a new ST called ST38. CONCLUSION: The present study genotyped B. henselae samples isolated from stray cats in Turkey for the first time and ST1, ST5, ST9, ST35, and ST36 as well as a new sequence type named ST38 were identified among these B. henselae isolates.

Single-nucleotide polymorphisms in ialB, gltA and rpoB genes of Bartonella bacilliformis isolated from patients in endemic Peruvian regions.

Bartonella bacilliformis is a Gram-negative, aerobic bacterium and the known causal agent of Carrion's disease, still considered a neglected disease. There is limited information about the nucleotide sequences of this bacterium in international databases, and few studies have addressed the genetic diversity of B. bacilliformis. We analyzed a total of 20 isolates of B. bacilliformis from the Peruvian regions of Ancash and Cajamarca. Three genes (ialB, gltA, and rpoB) were sequenced in each isolate and nucleotide sequences retrieved from GenBank (16 B. bacilliformis genomes) were also included in the study. All this information was merged in order to obtain clearer evidence of the phylogenetic relationships of B. bacilliformis. In the phylogenetic analysis conducted with the concatenated markers, four isolates (B.b-1, B. b-3, B. b- 7, B.b-8) from the Ancash region were observed to form a subgroup different from B. bacilliformis type strain KC583, showing dissimilarity levels of 5.96% (ialB), 3.69% (gltA) and 3.04% (rpoB). Our results suggest that B. bacilliformis consists of two different subgroups. Future investigations are needed to establish the taxonomic status of these subgroups.

Bartonella Infection in Fruit Bats and Bat Flies, Bangladesh.

Bats harbor diverse intracellular Bartonella bacteria, but there is limited understanding of the factors that influence transmission over time. Investigation of Bartonella dynamics in bats could reveal general factors that control transmission of multiple bat-borne pathogens, including viruses. We used molecular methods to detect Bartonella DNA in paired bat (Pteropus medius) blood and bat flies in the family Nycteribiidae collected from a roost in Faridpur, Bangladesh between September 2020 and January 2021. We detected high prevalence of Bartonella DNA in bat blood (35/55, 64%) and bat flies (59/60, 98%), with sequences grouping into three phylogenetic clades. Prevalence in bat blood increased over the study period (33% to 90%), reflecting an influx of juvenile bats in the population and an increase in the prevalence of bat flies. Discordance between infection status and the clade/genotype of detected Bartonella was also observed in pairs of bats and their flies, providing evidence that bat flies take blood meals from multiple bat hosts. This evidence of bat fly transfer between hosts and the changes in Bartonella prevalence during a period of increasing nycteribiid density support the role of bat flies as vectors of bartonellae. The study provides novel information on comparative prevalence and genetic diversity of Bartonella in pteropodid bats and their ectoparasites, as well as demographic factors that affect Bartonella transmission and potentially other bat-borne pathogens.

Bartonella infections are prevalent in rodents despite efficient immune responses.

BACKGROUND: Pathogens face strong selection from host immune responses, yet many host populations support pervasive pathogen populations. We investigated this puzzle in a model system of Bartonella and rodents from Israel's northwestern Negev Desert. We chose to study this system because, in this region, 75-100% of rodents are infected with Bartonella at any given time, despite an efficient immunological response. In this region, Bartonella species circulate in three rodent species, and we tested the hypothesis that at least one of these hosts exhibits a waning immune response to Bartonella, which allows reinfections. METHODS: We inoculated captive animals of all three rodent species with the same Bartonella strain, and we quantified the bacterial dynamics and Bartonella-specific immunoglobulin G antibody kinetics over a period of 139 days after the primary inoculation, and then for 60 days following reinoculation with the same strain. RESULTS: Contrary to our hypothesis, we found a strong, long-lasting immunoglobulin G antibody response, with protective immunological memory in all three rodent species. That response prevented reinfection upon exposure of the rodents to the same Bartonella strain. CONCLUSIONS: This study constitutes an initial step toward understanding how the interplay between traits of Bartonella and their hosts influences the epidemiological dynamics of these pathogens in nature.

Molecular evidence of Bartonella spp. in wild lowland tapirs (Tapirus terrestris), the largest land mammals in Brazil.

The genus Bartonella (Hyphomicrobiales: Bartonellaceae) encompasses facultative intracellular α-proteobacteria that parasite erythrocytes and endothelial cells from a wide range of vertebrate hosts and can cause disease in animals and humans. Considering the large diversity of vertebrate species that may act as reservoirs and arthropod species that may be associated with Bartonella transmission, the exposure of animals and humans to these microorganisms is likely underestimated. The present study aimed to investigate the occurrence of Bartonella sp. in wild tapirs (Tapirus terrestris; Perissodactyla: Tapiridae) from two biomes in Brazil: Pantanal and Cerrado. Ninety-nine GPS-monitored wild tapirs were sampled in Pantanal (n = 61/99) and Cerrado (n = 38/99). A qPCR (quantitative real-time polymerase chain reaction) assay targeting the nuoG gene was used for the screening for Bartonella spp. DNA. Positive samples were additionally subjected to conventional PCR assays targeting five molecular markers (ribC, gltA, rpoB, groEL, ITS). Eight (8/99; 08,08%) animals were positive in the qPCR assay for Bartonella spp.: 7 from Cerrado (7/8; 87.5%) and 1 from Pantanal (1/8; 12.5%). The 5 Bartonella ribC sequences obtained from tapirs' blood samples grouped together with Bartonella henselae obtained from cats, humans, wild felids and Ctenocephalides felis (Siphonaptera: Pulicidae) fleas. To the best of author's knowledge, this is the first report of Bartonella sp. in Tapirus terrestris. This finding contributes to the understanding of the occurrence of B henselae in wild mammals from Brazil as well as expands the knowledge regarding the potential vector-borne pathogens that may affect wild tapis from Cerrado and Pantanal biomes.

Molecular detection and characterization of Bartonella spp. in rodents from central and southern Chile, with emphasis on introduced rats (Rattus spp.).

Bartonella spp. was screened in 155 rodents from Chile, mainly the invasive rats Rattus norvegicus and Rattus rattus. A total of 155 spleen and 50 blood samples were analyzed through real-time PCR for Bartonella spp. (nuoG gene). Positive samples were subjected to amplification of fragment of loci gltA, rpoB and ITS by conventional PCR (cPCR). Overall, 43 spleen samples (27.7%) and 6 rodent blood samples (12%) were positive for nuoG-Bartonella spp. Positive samples were found in R. norvegicus, R. rattus, Abrothrix olivacea and Oligoryzomys longicaudatus. Bartonella spp. DNA was amplified by cPCR in 16 samples, resulting in 21 sequences (6 gltA, 5 ITS and 10 rpoB). Sequencing and phylogenic analyses identified genotypes from Rattus spp., potentially belonging to Bartonella coopersplainsensis, Bartonella henselae, Bartonella tribocorum, and an undescribed Bartonella sp. From native rodents, one sequence was identified, being related B. machadoae. In conclusion, this work describes diverse and potentially zoonotic Bartonella spp. genotypes in Rattus spp. Additionally, this is the first report of Bartonella in O. longicaudatus, including a potentially novel Bartonella genotype or species.

The diverse genetic genotypes of Bartonella species circulating in rodents from Inner Mongolia, Northern China.

Bartonella are generally recognized as zoonotic pathogens of mammals, including many rodent species. However, data on the genetic diversity of Bartonella in some regions are still absent in China. In this study, we collected rodent samples (Meriones unguiculatus, Spermophilus dauricus, Eolagurus luteus, and Cricetulus barabensis) from Inner Mongolia located in Northern China. The Bartonella were detected and identified by sequencing the gltA, ftsZ, ITS, and groEL genes in them. An overall 47.27% (52/110) positive rate was observed. This may be the first report that M. unguiculatus and E. luteus harbor Bartonella. Phylogenetic and genetic analysis on gltA, ftsZ, ITS, and groEL genes indicated that the strains were divided into seven distinct clades, suggesting the diverse genetic genotypes of Bartonella species in this area. Of those, Clade 5 meets the criteria for identification as a novel species based on gene sequence dissimilarity to known Bartonella species and herein we name it "Candidatus Bartonella mongolica".

Risk Factors for Bartonella Seroreactivity Among Veterinary Workers in the Pacific Northwest.

Background: Exposure to zoonotic diseases is a significant occupational risk in veterinary medicine. In this study, we characterized personal protective equipment use, injury frequency, and Bartonella seroreactivity in Washington State veterinary workers. Methods: Using a risk matrix developed to reflect occupational risk factors for exposure to Bartonella and multiple logistic regression, we explored determinants of risk for Bartonella seroreactivity. Results: Depending on the titer cutoff used, Bartonella seroreactivity was between 24.0% and 55.2%. No significant predictors of seroreactivity were found, although the relationship between high-risk status and increased seroreactivity for some Bartonella species approached significance. Serology for other zoonotic and vector borne pathogens did not identify consistent cross reactivity with Bartonella antibodies. Conclusion: The predictive power of the model was likely limited by the small sample size and high level of exposure to risk factors for most participants. Given the high proportion of veterinarians seroreactive to one or more of the three Bartonella spp. known to infect dogs and cats in the United States, as well as seroreactivity to other zoonoses, and the unclear relationship between occupational risk factors, seroreactivity, and disease expression, more research is needed in this area.

Comparison of molecular methods for Bartonella henselae detection in blood donors.

The Bartonella genus consists of neglected pathogens associated with potentially transfusional-transmitted and fatal human diseases. We aimed to evaluate Bartonella sp. prevalence in 500 blood donors and compare the results with the data already published about these samples. We used molecular diagnostic methods to detect Bartonella sp.-DNA from blood and liquid culture samples: (A) conventional PCR for two gene regions, the ITS targeting the genus Bartonella and the specific gltA Bartonella henselae; (B) nested PCR for the ftsZ gene and (C) qualitative real-time PCR for the gltA gene, both B. henselae specific. We obtained 30/500 (6%) DNA detections from the blood samples; 77/500 (15.4%) DNA detections from liquid culture samples and five (1%) samples had DNA detection from both. In total, we detected B. henselae DNA from 102/500 (20.4%) donors. The samples used in this study had already been submitted for Bartonella sp.-DNA detection using only a conventional PCR in liquid culture. Sixteen samples (3.2%) were positive previously, and from these 16 samples, 13 were negative in the new investigation. We concluded that the use of liquid culture combined with different molecular tests increases the possibility of detecting Bartonella sp.-DNA, but the tests do not avoid false-negative results. More than a fifth of blood donors had at least one PCR that detected Bartonella sp.-DNA among the eight molecular reactions performed now (four reactions in whole blood and four in liquid culture). Seven percent had B. henselae-DNA detection for two or more distinct regions. Considering the results obtained previously, the DNA of Bartonella spp. was detected or the agent isolated in 23% of analyzed blood donors. The results establish that the low bacteremia and the fastidious characteristics of the bacterium are challenges to laboratory diagnosis and can make it difficult to confirm the infection in patients with bartonelloses.

Profiling Bartonella infection and its associated risk factors in shelter cats in Malaysia.

BACKGROUND: Poor disease management and irregular vector control could predispose sheltered animals to disease such as feline Bartonella infection, a vector-borne zoonotic disease primarily caused by Bartonella henselae. OBJECTIVES: This study investigated the status of Bartonella infection in cats from eight (n = 8) shelters by molecular and serological approaches, profiling the CD4:CD8 ratio and the risk factors associated with Bartonella infection in shelter cats. METHODS: Bartonella deoxyribonucleic acid (DNA) was detected through polymerase chain reaction (PCR) targeting 16S-23S rRNA internal transcribed spacer gene, followed by DNA sequencing. Bartonella IgM and IgG antibody titre, CD4 and CD8 profiles were detected using indirect immunofluorescence assay and flow cytometric analysis, respectively. RESULTS: B. henselae was detected through PCR and sequencing in 1.0% (1/101) oral swab and 2.0% (1/50) cat fleas, while another 3/50 cat fleas carried B. clarridgeiae. Only 18/101 cats were seronegative against B. henselae, whereas 30.7% (31/101) cats were positive for both IgM and IgG, 8% (18/101) cats had IgM, and 33.7% (34/101) cats had IgG antibody only. None of the eight shelters sampled had Bartonella antibody-free cats. Although abnormal CD4:CD8 ratio was observed in 48/83 seropositive cats, flea infestation was the only significant risk factor observed in this study. CONCLUSIONS: The present study provides the first comparison on the Bartonella spp. antigen, antibody status and CD4:CD8 ratio among shelter cats. The high B. henselae seropositivity among shelter cats presumably due to significant flea infestation triggers an alarm of whether the infection could go undetectable and its potential transmission to humans.