Brucella taxonomy and evolution

[Brucella spondylodiscitis and factors associated with prognosis: a case series from Sétif, Algeria]

Introduction and objectives

Spondylodiscitis is a serious and suggestive complication of brucellosis. Few studies have been devoted to it in Algeria, although the infection remains a public health problem. The aim of this study was to report the epidemiological and clinical aspects of brucellosis spondylodiscitis and to identify the neurological complications.

Material and methods

This is a descriptive analysis of a cohort of adult patients with Brucella spondylodiscitis, based on data collected from patient records recruited between January 2016 and December 2022.

Results

Thirteen females and 24 males with a mean age of 48 ± 15 years [21 to 71 years] were included in the study. Diagnosis was made on average 120 days ± 100 [30-360] after the onset of clinical symptoms. Commonly reported symptoms were: back pain (100%), fever (46%), sweating (70%), asthenia (84%), chills (22%), and weight loss (27%). Neurological complications were numerous and sometimes varied in the same patient: one case of paraplegia, three cases of paraparesis, six cases of sensory disturbances, and one case of sphincter disorders. Involvement of the lumbar spine was predominant, observed in 22 patients, including 15 at the L4-L5 level.In addition to discovertebral lesions, imaging revealed 27 cases of epiduritis, 13 cases of spinal cord compression, 25 cases of radicular compression, and pre- or para-vertebral and psoas abscesses.Two treatment regimens were used: doxycycline-cotrimoxazole-gentamycin (22 cases) and doxycycline-rifampicin-gentamycin (15 cases). At the end of the one-year post-therapeutic follow-up, we observed one relapse, sequelae of paraparesis, and sequelae of spinal pain in 12 patients.

Discussion and conclusion

This study has allowed us to observe prognostic elements. Early spinal imaging is essential to combat the excessive delay in diagnosis in our patients. There is no clear consensus in the scientific literature regarding neurological complications, such as epiduritis, and optimal treatment. The results of our study may contribute to the development of more personalized management algorithms.

RIBAP: a comprehensive bacterial core genome annotation pipeline for pangenome calculation beyond the species level

Microbial pangenome analysis identifies present or absent genes in prokaryotic genomes. However, current tools are limited when analyzing species with higher sequence diversity or higher taxonomic orders such as genera or families. The Roary ILP Bacterial core Annotation Pipeline (RIBAP) uses an integer linear programming approach to refine gene clusters predicted by Roary for identifying core genes. RIBAP successfully handles the complexity and diversity of Chlamydia, Klebsiella, Brucella, and Enterococcus genomes, outperforming other established and recent pangenome tools for identifying all-encompassing core genes at the genus level. RIBAP is a freely available Nextflow pipeline at github.com/hoelzer-lab/ribap and zenodo.org/doi/10.5281/zenodo.10890871.

Effector Proteins of Type IV Secretion System: Weapons of Brucella Used to Fight Against Host Immunity

Brucella is an intracellular bacterial pathogen capable of long-term persistence in the host, resulting in chronic infections in livestock and wildlife. The type IV secretion system (T4SS) is an important virulence factor of Brucella and is composed of 12 protein complexes encoded by the VirB operon. T4SS exerts its function through its secreted 15 effector proteins. The effector proteins act on important signaling pathways in host cells, inducing host immune responses and promoting the survival and replication of Brucella in host cells to promote persistent infection. In this article, we describe the intracellular circulation of Brucella-infected cells and survey the role of Brucella VirB T4SS in regulating inflammatory responses and suppressing host immune responses during infection. In addition, the important mechanisms of these 15 effector proteins in resisting the host immune response during Brucella infection are elucidated. For example, VceC and VceA assist in achieving sustained survival of Brucella in host cells by affecting autophagy and apoptosis. BtpB, together with BtpA, controls the activation of dendritic cells during infection, induces inflammatory responses, and controls host immunity. This article reviews the effector proteins secreted by Brucella T4SS and their involvement in immune responses, which can provide a reliable theoretical basis for the subsequent mechanism of hijacking the host cell signaling pathway by bacteria and contribute to the development of better vaccines to effectively treat Brucella bacterial infection.

A novel, highly sensitive, one-tube nested quantitative real-time PCR for Brucella in human blood samples

IMPORTANCE

This study developed a highly sensitive and efficient method for the detection of brucellosis by introducing a one-tube nested quantitative real-time PCR (qPCR) approach, representing a remarkable advance in the field. The method demonstrated an impressive analytical sensitivity of 100 fg/μL, surpassing conventional qPCR and enabling the detection of even low levels of Brucella DNA. In addition, the study's comprehensive evaluation of 250 clinical samples revealed a specificity of 100% and a sensitivity of 98.6%, underscoring its reliability and accuracy. Most importantly, the new method significantly improved the detection rate of low-burden samples, reducing cycle threshold values by an average of 6.4. These results underscore the immense potential of this approach to facilitate rapid and accurate brucellosis diagnosis, which is critical for effective disease management and control.

Immuno-profiling of Brucella proteins for developing improved vaccines and DIVA capable serodiagnostic assays for brucellosis

Brucellosis remains a worldwide zoonotic disease with a serious impact on public health and livestock productivity. Controlling brucellosis in livestock is crucial for limiting human infections in the absence of effective human vaccines. Brucellosis control measures are majorly dependent on rigorous monitoring of disease outbreaks and mass vaccination of livestock. Live attenuated vaccines are available for livestock vaccination that play a vital role in brucellosis control programs in many countries. Even though the existing animal vaccines confer protection against brucellosis, they carry some drawbacks, including their infectivity to humans and interference with sero-monitoring. The available serodiagnostic assays for brucellosis depend on detecting anti-LPS antibodies in the serum. Since diagnosis plays a vital role in controlling brucellosis, developing improved serodiagnostic assays with enhanced specificity, sensitivity and DIVA capability is required. Therefore, it is essential to identify novel antigens for developing improved vaccines and serodiagnostic assays for brucellosis. In the present study, we performed a high throughput immunoprofiling of B. melitensis protein microarray using brucellosis-positive human and animal serum samples. The screening identified several serodominant proteins of Brucella that exhibited common or differential reactivity with sera from animals and humans. Subsequently, we cloned, expressed, and purified ten serodominant proteins, followed by analyzing their potential to develop next-generation vaccines and improved serodiagnostic assays for brucellosis. Further, we demonstrated the protective efficacy of one of the serodominant proteins against the B. melitensis challenge in mice. We found that the seroreactive protein, Dps (BMEI1980), strongly reacted with brucellosis-positive serum samples, but it did not react with sera from B. abortus S19-vaccinated cattle, indicating DIVA capability. A prototype lateral flow assay and indirect ELISA based on Dps protein exhibited high sensitivity, specificity, and DIVA capability. Thus, the present study identified promising candidates for developing improved vaccines and affordable, DIVA-capable serodiagnostic assays for animal and human brucellosis.

The Brucella Effector Protein BspF Regulates Apoptosis through the Crotonylation of p53

The Brucella type IV secretion system (T4SS) can promote the intracellular survival and reproduction of Brucella. T4SS secretes effector proteins to act on cellular signaling pathways to inhibit the host's innate immune response and cause a chronic, persistent Brucella infection. Brucella can survive in host cells for a long time by inhibiting macrophage apoptosis and avoiding immune recognition. The effector protein, BspF, secreted by T4SS, can regulate host secretory transport and accelerate the intracellular replication of Brucella. BspF has an acetyltransferase domain of the GNAT (GCN5-related N-acetyltransferases) family, and in our previous crotonylation proteomics data, we have found that BspF has crotonyl transferase activity and crotonylation regulation of host cell protein in the proteomics data. Here, we found that BspF attenuates the crotonylation modification of the interacting protein p53, which reduces the p53 expression through the GNAT domain. BspF can inhibit the transcription and protein expression of downstream apoptotic genes, thereby inhibiting host cell apoptosis. Additionally, the Brucella ΔbspF mutant stain promotes apoptosis and reduces the survival rate of Brucella in the cells. In conclusion, we identified that the T4SS effector protein BspF can regulate host cell apoptosis to assist Brucella in its long-term survival by attenuating crotonylation modification of p53 and decreasing p53 expression. Our findings reveal a unique mechanism of elucidating how Brucella regulates host cell apoptosis and promotes its proliferation through the secretion of effector proteins.

Comparative evaluation of RBPT, I-ELISA, and CFT for the diagnosis of brucellosis and PCR detection of Brucella species from Ethiopian sheep, goats, and cattle sera

BACKGROUND

Brucellosis is an economically devastating animal disease and has public health concern. Serological methods such as Rose Bengal Plate Test (RBPT), Complement Fixation Test (CFT), and Indirect-Enzyme-Linked Immunosorbent Assay (I-ELISA) have been used to detect brucellosis. However, there is limited comparative evaluation studies and lack of molecular confirmation of the causative agents in the study areas. The study was aimed to compare RBPT, I-ELISA, CFT, and confirmation using Polymerase Chain Reaction (PCR). A total of 2317 sera samples were collected from brucellosis-affected areas of Ethiopia with no vaccination history. All sera were subjected to comparative serological assays. Post-cross tabulation, sensitivity, and specificity were determined using Receiver Operating Characteristics (ROC) curve analysis software. PCR was performed on 54 seropositive samples using genus- and species-specific primers.

RESULTS

Among the 2317 sera tested for comparative serological assays, 189 (8.16%) were positive for RBPT, 191 (8.24%) for I-ELISA, and 48 (2.07%) for CFT. Sensitivity to RBPT was 100% (95%) in shoats and 74% (95%) in cattle. Specificity on RBPT was 98.69% (95%), 99.28% (95%), 100% (95%) in sheep, goats, and cattle, respectively. CFT sensitivity was 4 (95%) in sheep, 9.65 (95%) goats, and 72 (95%) cattle. Specificity on CFT was 100% (95%) for sheep, goats, and cattle. A 223bp Brucella genus-specific and 156bp B. abortus species-specific detected. However, B. melitensis not detected.

CONCLUSION

In this study, I-ELISA was the most sensitive and specific test. RBPT detected all Brucellosis-infected sheep and goats; nevertheless, it showed false positive in sheep and goats and false negative in cattle. The presence of B. abortus in small and large ruminants was confirmed by PCR. This is the first report of B. abortus detection in small ruminant in Ethiopia. B.abortus detected in non-preferred hosts. The findings suggest further study on molecular epidemiology of Brucella species.

Molecular epidemiological characteristics of Brucella in Guizhou Province, China, from 2009 to 2021

Introduction

Brucellosis was made statutorily notifiable in 1955, in China, while in Guizhou Province, the pathogen of human brucellosis was isolated for the first time in 2011. However, currently, the brucellosis epidemic is becoming more and more severe in Guizhou Province. The type distribution and genetic characteristics of Brucella in Guizhou Province, as well as its evolutionary relationship with domestic and foreign strains, are still unclear.

Methods

MLST, MLVA, and rpoB typing techniques were used for the molecular epidemiological study of the 83 Brucella isolates in Guizhou province.

Results

Among the 83 Brucella strains, MLST identified three ST genotypes, of which ST39 is a newly reported type in China. MLVA-16 generated 49 genotypes, and MLVA-11 generated 5 known genotypes and 2 unreported genotypes. Six genotypes were identified by rpoB technology.

Discussion

MLVA has a high resolution, but differences at the Bruce 04 and 16 loci cannot exclude associations between epidemics, and combining MLST and rpoB typing methods for epidemiologic tracing can avoid erroneous judgments. Moreover, through the combined analysis of the three typing techniques, the possible origin of the new Brucella can be reasonably inferred, which is also conducive to promoting the subsequent research of the novel Brucella.

Genomic distribution of the insertion sequence IS711 reveal a potential role in Brucella genome plasticity and host preference

The Insertion Sequence 711 (IS711) is linked to the Brucella genus. Mapping the genomic distribution of IS711 can help understand this insertion element's biological and evolutionary role. This work aimed to delineate the genomic distribution of the IS711 element and to study its association with Brucella evolution. A total of 124 genomes representing 9 Brucella species were searched using BLASTn sequence alignment tool to identify complete and truncated copies of IS711. Based on the genomic context, each IS711 locus was assigned a code using the initial letters of its neighboring genes. Various tools were used to annotate the neighboring genes and determine the shared synteny around orthologous IS711 loci. The tool Islandviewer 4 was used to scan for genomic islands. The Codon Tree method was used to build phylogenetic trees of B. melitensis, B. abortus, and B. suis genomes. The phylogenetic trees of the three species were analyzed, taking into account the genomic distribution patterns of IS711. The result of IS711 frequency analysis showed a relatively conserved number of copies/genome for the different species and for some biovars. The analysis showed that Brucella species with a relatively low IS711 copy number (4-8 copies/genome) are linked to domestic animals as primary hosts and have potential for zoonotic transmission. However, species with a relatively higher copy number (12-30 copies/genome) are less zoonotic and tend to be linked with wild animals as primary hosts. Analyzing the genomic distribution map of IS711 loci showed several unique patterns of IS711 distribution that are correlated with the evolution of Brucella species and biovars. The results also showed that 46.2% of the conserved IS711 elements are located within genomic islands. Based on our results and previous data, we postulate a model explaining the IS711 role in Brucella evolution. We assume that during the transition from a free-living to an intracellular lifestyle, a descendant of the Brucella genus had acquired a progenitor sequence of the IS711. Subsequently, a burst in IS711 transposition occurred. This parasitic expansion can be deleterious and has to be counteracted by evolutionary forces to prevent lineage extension and to promote adaptation to host. Similar to other plasmid-free pathogenic α-Proteobacteria bacteria, the balance of expansion and reduction of insertion elements could be one of the mechanisms to control genome reduction and streamlining. We hypothesize that the IS711-mediated genomic changes and other small sequence nucleotide changes in specific orthologous genes could significantly contribute to Brucella's evolution and adaptation to different animal hosts.

Cell and Tissue Tropism of Brucella spp

Brucella spp. are facultatively intracellular bacteria that can infect, survive, and multiply in various host cell types in vivo and/or in vitro. The genus Brucella has markedly expanded in recent years with the identification of novel species and hosts, which has revealed additional information about the cell and tissue tropism of these pathogens. Classically, Brucella spp. are considered to have tropism for organs that contain large populations of phagocytes such as lymph nodes, spleen, and liver, as well as for organs of the genital system, including the uterus, epididymis, testis, and placenta. However, experimental infections of several different cultured cell types indicate that Brucella may actually have a broader cell tropism than previously thought. Indeed, recent studies indicate that certain Brucella species in particular hosts may display a pantropic distribution in vivo. This review discusses the available knowledge on cell and tissue tropism of Brucella spp. in natural infections of various host species, as well as in experimental animal models and cultured cells.

Tracking the distribution, genetic diversity and lineage of Brucella melitensis recovered from humans and animals in Egypt based on core-genome SNP analysis and in silico MLVA-16

Brucellosis is one of the most common neglected zoonotic diseases globally, with a public health significance and a high economic loss in the livestock industry caused by the bacteria of the genus Brucella. In this study, 136 Egyptian Brucella melitensis strains isolated from animals and humans between 2001 and 2020 were analysed by examining the whole-core-genome single-nucleotide polymorphism (cgSNP) in comparison to the in silico multilocus variable number of tandem repeat analysis (MLVA-16). Almost all Egyptian isolates were belonging to the West Mediterranean clade, except two isolates from buffalo and camel were belonging to the American and East Mediterranean clades, respectively. A significant correlation between the human case of brucellosis and the possible source of infection from animals was found. It seems that several outbreak strains already existing for many years have been spread over long distances and between many governorates. The cgSNP analysis, in combination with epidemiological metadata, allows a better differentiation than the MLVA-16 genotyping method and, hence, the source definition and tracking of outbreak strains. The MLVA based on the currently used 16 markers is not suitable for this task. Our results revealed 99 different cgSNP genotypes with many different outbreak strains, both older and widely distributed ones and rather newly introduced ones as well. This indicates several different incidents and sources of infections, probably by imported animals from other countries to Egypt. Comparing our panel of isolates to public databases by cgSNP analysis, the results revealed near relatives from Italy. Moreover, near relatives from the United States, France, Austria and India were found by in silico MLVA.

Brucellosis in small ruminant: seroprevalence, risk factors, and distribution in the southeast of Algeria

The impact of brucellosis on public health and economy is unquestionable in developing countries such as the case of Algeria. This study aimed to provide further understanding of epidemiological status of brucellosis in small ruminant flocks in the southeast of Algeria. Therefore, a cross-sectional study was conducted among small ruminant flocks (n = 51) in El Oued district using simple random sampling strategy. The serum samples collected from 612 sheep and goats (sheep = 280, goats = 332) were screened for Brucella antibodies using the Rose Bengal test (RBT) and the indirect enzyme-linked immunosorbent assay (iELISA) in parallel on all the serum samples. The seropositive serum samples of both tests were confirmed with the complement fixation test (CFT). A structured questionnaire regarding animal, herd, and farm management was prepared and completed in parallel to sampling. Association between variables and Brucella spp. seropositivity status of herds was assessed by univariate and multivariate analysis using simple and binary logistic regression. Estimated true herd prevalence was 27.95% (95% CI, 17.18-42.01), and true individual prevalence was 3.98% (95% CI, 2.51-6.03). Seropositive herds were detected in bordering areas and regions with the highest livestock density. Occurrence of abortions in herds (p = 0.03) increased at least five times (5) the odds of being seropositive (OR, 6.25; 95% CI, 1.20-32.46). Poultry presence in farms revealed to be a protective factor (p = 0.01) (OR, 0.11; 95% CI, 0.02-0.61). The high-level seroprevalence quantified in this study in small ruminant flocks reflects the persistent animal infection endemicity and the high risk of human exposure.

Epitope-Based Vaccine of a Brucella abortus Putative Small RNA Target Induces Protection and Less Tissue Damage in Mice

Brucella spp. are Gram-negative, facultative intracellular bacteria that cause brucellosis in humans and animals. Currently available live attenuated vaccines against brucellosis still have drawbacks. Therefore, subunit vaccines, produced using epitope-based antigens, have the advantage of being safe, cost-effective and efficacious. Here, we identified B. abortus small RNAs expressed during early infection with bone marrow-derived macrophages (BMDMs) and an apolipoprotein N-acyltransferase (Int) was identified as the putative target of the greatest expressed small RNA. Decreased expression of Int was observed during BMDM infection and the protein sequence was evaluated to rationally select a putative immunogenic epitope by immunoinformatic, which was explored as a vaccinal candidate. C57BL/6 mice were immunized and challenged with B. abortus, showing lower recovery in the number of viable bacteria in the liver, spleen, and axillary lymph node and greater production of IgG and fractions when compared to non-vaccinated mice. The vaccinated and infected mice showed the increased expression of TNF-α, IFN-γ, and IL-6 following expression of the anti-inflammatory genes IL-10 and TGF-β in the liver, justifying the reduction in the number and size of the observed granulomas. BMDMs stimulated with splenocyte supernatants from vaccinated and infected mice increase the CD86+ marker, as well as expressing greater amounts of iNOS and the consequent increase in NO production, suggesting an increase in the phagocytic and microbicidal capacity of these cells to eliminate the bacteria.

The one hundred year journey of the genus Brucella (Meyer and Shaw 1920)

The genus Brucella, described by Meyer and Shaw in 1920, comprises bacterial pathogens of veterinary and public health relevance. For 36 years, the genus came to include three species that caused brucellosis in livestock and humans. In the second half of the 20th century, bacteriologists discovered five new species and several 'atypical' strains in domestic animals and wildlife. In 1990, the Brucella species were recognized as part of the Class Alphaproteobacteria, clustering with pathogens and endosymbionts of animals and plants such as Bartonella, Agrobacterium and Ochrobactrum; all bacteria that live in close association with eukaryotic cells. Comparisons with Alphaproteobacteria contributed to identify virulence factors and to establish evolutionary relationships. Brucella members have two circular chromosomes, are devoid of plasmids, and display close genetic relatedness. A proposal, asserting that all brucellae belong to a single species with several subspecies debated for over 70 years, was ultimately rejected in 2006 by the subcommittee of taxonomy, based on scientific, practical, and biosafety considerations. Following this, the nomenclature of having multiples Brucella species prevailed and defined according to their molecular characteristics, host preference, and virulence. The 100-year history of the genus corresponds to the chronicle of scientific efforts and the struggle for understanding brucellosis.

Genetic identification of the causative agent of Brucellosis

The development of animal husbandry suffers various kinds of losses due to the spread of infectious diseases among animals, in particular Brucellosis. A challenge faced by Brucella researchers has been the accurate identification of new isolates within the genus while preserving sufficient, and not excessive, biosafety and biosecurity requirements. The availability of discriminatory molecular typing tools to inform and assist conventional epidemiological approaches would be invaluable in controlling these infections, but efforts have been hampered by the genetic homogeneity of the genus. In this work, for better identification of infection, for control and monitor the source of outbreaks in prosperous areas was carried out identification of Brucella spp. strains which circulating in the Kostanay region. For this was used using multilocus analysis of a variable number of tandem repeats sequenced by 16 s – PNK on a genetic analyzer (sequencer). According to the results of a study of cattle, cultures of microorganisms were infected: No. 4, 5, 7, 8. Comparison of the obtained results with similar results of domestic and foreign works by A. Shevtsov, G. Borrello, P. Le Fleche, G. Garofolo suggest that the genotyping of local strains has an importance in the molecular epizootology of the Republic of Kazakhstan.

Adhesive Functions or Pseudogenization of Type Va Autotransporters in Brucella Species

Adhesion to host cells is a key step for successful infection of many bacterial pathogens and may define tropism to different host tissues. To do so, bacteria display adhesins on their surfaces. Brucella is an intracellular pathogen capable of proliferating in a wide variety of cell types. It has been described that BmaC, a large protein that belongs to the classical (type Va) autotransporter family, is required for efficient adhesion of Brucella suis strain 1330 to epithelial cells and fibronectin. Here we show that B. suis 1330 harbors two other type Va autotransporters (BmaA and BmaB), which, although much smaller, share significant sequence similarities with BmaC and contain the essential domains to mediate proper protein translocation to the bacterial surface. Gain and loss of function studies indicated that BmaA, BmaB, and BmaC contribute, to a greater or lesser degree, to adhesion of B. suis 1330 to different cells such as synovial fibroblasts, osteoblasts, trophoblasts, and polarized epithelial cells as well as to extracellular matrix components. It was previously shown that BmaC localizes to a single bacterial pole. Interestingly, we observed here that, similar to BmaC, the BmaB adhesin is localized mostly at a single cell pole, reinforcing the hypothesis that Brucella displays an adhesive pole. Although Brucella species have strikingly similar genomes, they clearly differ in their host preferences. Mainly, the differences identified between species appear to be at loci encoding surface proteins. A careful in silico analysis of the putative type Va autotransporter orthologues from several Brucella strains showed that the bmaB locus from Brucella abortus and both, the bmaA and bmaC loci from Brucella melitensis are pseudogenes in all strains analyzed. Results reported here evidence that all three autotransporters play a role in the adhesion properties of B. suis 1330. However, Brucella spp. exhibit extensive variations in the repertoire of functional adhesins of the classical autotransporter family that can be displayed on the bacterial surface, making them an interesting target for future studies on host preference and tropism.

A time-resolved fluorescence lateral flow immunoassay for rapid and quantitative serodiagnosis of Brucella infection in humans

Brucellosis is a worldwide infectious zoonotic disease, posing severe threats to human health and social-economic development. By comparing with time-consuming, low sensitive and non-quantitative conventional serological methods, herein, protein G (prG) coupled with europium nanospheres (EuNPs) (detection probe) and highly purified Brucella lipopolysaccharide (LPS) (capture antigen) were used to develop a novel time-resolved fluorescence lateral flow immunoassay (TF-LFIA) for detecting anti-Brucella IgG antibody in human plasmas. The entire testing took 15 min. With a satisfactory purity, the purified LPS weakly cross-reacted with Y. enterocolitica O9 diagnostic antibody; however, none reacted with sera from patients with other Gram-negative bacterial infections. Following coefficient of determination (R² = 0.9961), 0.3 IU/mL was reported as the limit of detection (LOD), much lower than those of Serological Agglutination Test (SAT), Rose-Bengal Plate Agglutination Test (RBPT) and colloidal gold LFIA (CG-LFIA). Intra-day and inter-day precisions (CV, coefficient variation) of TF-LFIA varied less than 8% or 12 %, while intra-day and inter-day accuracies were 94-106 % or 93-107 %, respectively. The correlation coefficient (R²) of TF-LFIA measurement to the different concentrations of spiked Brucella antibody was 0.9967, suggesting TF-LFIA had high reliability and reproducibility. TF-LFIA was demonstrated for 100 % specificity, 98.57 % sensitivity and 99.63 % accuracy in detection of Brucella antibody from clinical samples, respectively, significantly higher compared to SAT and RBPT. In conclusion, the established TF-LFIA is a simple, rapid and quantitative immunoassay for early diagnosis or epidemiological surveillance of Brucella infection in humans.

Scenario of pathogenesis and socioeconomic burden of human brucellosis in Saudi Arabia

Brucellosis is considered a prevailing endemic infectious disease in the Kingdom of Saudi Arabia and represents a health problem with socio-economic burden. There are two main Brucella species that cause human brucellosis; Brucella abortus, and Brucella melitensis. The clinical features range from asymptomatic to the acute symptoms of fever, joint pain, muscle pain, headache, nausea/vomiting, anorexia and malaise in addition to the subsequent complications that might occur. The endemicity of brucellosis might be explained due to obstacles in controlling the importation of animals for slaughtering during Hajj periods and for several other predisposing factors. The distribution of the disease is all over the country and the most prevalent part is the south followed by north and then the east and central parts. However, in the complexity of brucellosis control measures, there are several activities which have been implemented to tackle the disease such as mass vaccination of animals, regulating importation of slaughter animals, and improving public awareness. This review provides a detailed description of the status of brucellosis in Saudi Arabia, which includes epidemiology, clinical characteristics, virulence and pathophysiology, and prevention of the disease.

Genomic insights into Brucella

Brucellosis is a zoonotic disease caused by certain species of Brucella. Each species has its preferred host animal, though it can infect other animals too. For a longer period, only six classical species were recognized in the genus Brucella. No vaccine is available for human brucellosis. Therefore, human brucellosis can be controlled only by controlling brucellosis in animals. The genus is now expanding with the newly isolated atypical strains from various animals, including marine mammals. Presently, 12 species of Brucella have been recognized. The first genome of Brucella was released in 2002, and today, we have more than 1500 genomes of Brucella spp. isolated worldwide. Multiple genome sequences are available for the major zoonotic species, B. abortus, B. melitensis, and B. suis. The Brucella genome has two chromosomes with the approximate sizes of 2.1 and 1.2 Mbp. The genome of Brucella is highly conserved across all the species at the nucleotide level. One of the unanswered questions is what makes host preference in different species of Brucella. Here, I summarize the recent advancements in the Brucella genomics research.

Non-adaptive Evolution of Trimeric Autotransporters in Brucellaceae

Brucella species are Gram-negative, facultative intracellular pathogens. They are the main cause of brucellosis, which has led to a global health burden. Adherence of the pathogen to the host cells is the first step in the infection process. The bacteria can adhere to various biotic and abiotic surfaces using their outer membrane proteins. Trimeric autotransporter adhesins (TAAs) are modular homotrimers of various length and domain complexity. They are a diverse, and widespread gene family constituting the type Vc secretion pathway. These adhesins have been established as virulence factors in Brucellaceae. To date, no comprehensive and exhaustive study has been performed on the trimeric autotransporter family in the genus. In the present study, various bioinformatics tools were used to provide a novel evolutionary insight into the sequence and structure of this protein family in Brucellaceae. To this end, a dataset of all trimeric autotransporters from the Brucella genomes was built. Analyses included but were not limited to sequence alignment, phylogenetic tree constructions, codon-based test for selection, clustering of the sequences, and structure (primary to quaternary) predictions. Batch analyzes of the dataset suggested the existence of a few structural domains within the whole population. BatA from the B. abortus 2308 genome was selected as a reference to describe the features of these structural domains. Furthermore, we examined the structural basis for the observed rigidity and resiliency of the protein structure through a molecular dynamics evaluation, which led us to deduce that the random drift results in the non-adaptive evolution of the trimeric autotransporter genes in the Brucella genus. Notably, the modifications have occurred across the genus without interference of gene transmission.

Isolation and Identification of Two Brucella Species from a Volcanic Lake in Mexico

Brucellosis is a zoonosis caused by bacteria of the Brucella genus. Any source of contamination that could be infectious must be monitored to reduce the risk of exposure to brucellosis, so the purpose of this work was to determine the presence of Brucella spp. on surface water and tilapia (Oreochromis niloticus) skin from a volcanic lake in Mexico. A seasonal sampling during 2016-2017 was carried out at fifteen specific sites for water sampling and five sites for the collection of tilapia fish. From all water and fish samples tested, we found only three isolates of Brucella species. We isolated and identified B. abortus from surface water through bacteriological and molecular techniques, and B. abortus and B. suis from the same tilapia skin sample. The isolated strains likely came from breeding animals that are common to the region, such as infected pigs or cattle with Brucella abortus or B. suis, respectively. A similar finding has not been reported in a water from volcanic lake or tilapia fish in Mexico. We concluded that B. abortus and B. suis are present on the surface water of the volcanic lake and tilapia skin as possible contaminants derived from biological material from cows and pigs carrying this bacterium.

A safe non-toxic Brucella abortus ghosts induce immune responses and confer protection in BALB/c mice

Brucellosis, which is caused by Brucella spp., is an important zoonotic infectious disease that can cause great hazard to public health and safety. However, the current vaccines have several drawbacks, including residual virulence for animals and humans. Bacterial ghost is the empty envelopes of bacteria, which emerge as a proper vaccine candidate. With the purpose of generating B. abortus ghosts and investigating the immunogenicity of bacterial ghosts as vaccine candidate, we used homologous recombination and bacterial ghost technologies to construct 2308ΔgntR ghost strain. Mice were injected with 2308ΔgntR ghost and the safety and immunogenicity of ghost were further evaluated. The mice inoculated with ghost showed no splenomegaly. The 2308ΔgntR ghost induced high protective immunity in BALB/c mice against challenge with S2308, and elicited an anti-Brucella-specific immunoglobulin G (IgG) response and induced the secretion of interferon gamma (IFN-γ) and interleukin-4 (IL-4). Additionally, 2308ΔgntR ghost demonstrated strong spleen CD4⁺ and CD8⁺ T cell responses. These results suggest that 2308ΔgntR ghost is a potential vaccine candidate and may represent a promising new approach for vaccination against Brucella infection.

MLVA fingerprinting of Brucella melitensis circulating among livestock and cases of sporadic human illness in Egypt

Brucella melitensis is a serious public health threat, with human infection exhibiting acute febrile illness and chronic health problems. The present study investigated the genetic diversity and epidemiological links of the important zoonotic bacterium B. melitensis in Egypt using multilocus variable-number tandem repeat analysis (MLVA-16) including eight minisatellite (panel 1) and eight microsatellite (panel 2, subdivided into 2A and 2B) markers. A total of 118 isolates were identified as B. melitensis biovar 3 by classical biotyping and Bruce-ladder assay. Although B. melitensis is primarily associated with infection in sheep and goats, most of B. melitensis isolates in this study were obtained from secondary hosts (cattle, buffaloes, humans and a camel) suggesting cross-species adaptation of B. melitensis to large ruminants in Egypt. The MLVA-16 scheme competently discriminated 70 genotypes, with 51 genotypes represented by single isolates, and the remaining 19 genotypes were shared among 67 isolates, suggesting both sporadic and epidemiologically related characteristics of B. melitensis infection. Matching of local genotypes with representatives of global genotypes revealed that the majority of Egyptian isolates analysed had a West Mediterranean descendance. As this study represents the first comprehensive genotyping and genetic analysis of B. melitensis from different sources in Egypt, the information generated from this study will augment knowledge about the main epidemiological links associated with this bacterium and will allow a better understanding of the current epidemiological situation of brucellosis in Egypt. Ultimately, this will help to adopt effective brucellosis intervention strategies in Egypt and other developing nations.

Taxonomic Organization of the Family Brucellaceae Based on a Phylogenomic Approach

Deciphering the evolutionary history of pathogenic bacteria and their near neighbors may help to understand the genetic or ecological bases which led to their pathogenic behavior. The Brucellaceae family comprises zoonotic pathogenic species belonging to the genus Brucella as well as the environmental genus Ochrobactrum for which some species are considered as opportunistic pathogens. Here, we used a phylogenomic approach including a set of 145 Brucellaceae genomes representative of the family diversity and more than 40 genomes of the order Rhizobiales to infer the taxonomic relationships between the family’s species. Our results clarified some unresolved phylogenetic ambiguities, conducting to the exclusion of Mycoplana spp. out of the family Brucellaceae and the positioning of all Brucella spp. as a single genomic species within the current Ochrobactrum species diversity. Additional analyses also revealed that Ochrobactrum spp. separate into two clades, one comprising mostly environmental species while the other one includes the species considered as pathogens (Brucella spp.) or opportunistic pathogens (mainly O. anthropi, O. intermedium, and O. pseudintermedium). Finally, we show that O. intermedium is undergoing a beginning of genome reduction suggestive of an ongoing ecological niche specialization, and that some lineages of O. intermedium and O. anthropi may shift toward an adaption to the human host.

Laboratory Diagnosis of Human Brucellosis

The clinical presentation of brucellosis in humans is variable and unspecific, and thus, laboratory corroboration of the diagnosis is essential for the patient's proper treatment. The diagnosis of brucellar infections can be made by culture, serological tests, and nucleic acid amplification assays. Modern automated blood culture systems enable detection of acute cases of brucellosis within the routine 5- to 7-day incubation protocol employed in clinical microbiology laboratories, although a longer incubation and performance of blind subcultures may be needed for protracted cases. Serological tests, though they lack specificity and provide results that may be difficult to interpret in individuals repeatedly exposed to Brucella organisms, nevertheless remain a diagnostic cornerstone in resource-poor countries. Nucleic acid amplification assays combine exquisite sensitivity, specificity, and safety and enable rapid diagnosis of the disease. However, long-term persistence of positive molecular test results in patients that have apparently fully recovered is common and has unclear clinical significance and therapeutic implications. Therefore, as long as there are no sufficiently validated commercial tests or studies that demonstrate an adequate interlaboratory reproducibility of the different homemade PCR assays, cultures and serological methods will remain the primary tools for the diagnosis and posttherapeutic follow-up of human brucellosis.

A novel approach for detection of brucella using a real-time recombinase polymerase amplification assay

Brucella, the etiological agent of brucellosis, is an important zoonosis pathogen worldwide. Brucella infects humans and various domestic and wild animals, and represents a great threat to public health and animal husbandry. In the present study, we developed a real-time recombinase polymerase amplification (RPA) assay for the detection of Brucella. The assay targeted the bcsp31 gene of Brucella, and an RPA exo probe and a pair of primers were selected for assay validation. RPA sensitivity and specificity were evaluated using plasmid standards, Brucella representative strains, and non-Brucella strains. The RPA assay achieved a detection limit of 17 molecules in 95% of cases based on probit analysis, and could successfully distinguish 18 representative Brucella strains (B. abortus biovars 1, 2, 3, 4, 5, 6, 7 and 9, B. melitensis biovars 1, 2 and 3, B. suis biovars 1, 2, 3 and 4, B. canis, B. neotomae and B. ovis), and four Brucella vaccine strains (A19, S19, S2 and M5). A total of 52 Brucella field strains were detected by real-time PCR and RPA in parallel, and compared with real-time PCR, the sensitivity of the RPA assay was 94% (49/52). Thus, this RPA assay may be a rapid, sensitive, and specific tool for the prevention and control of Brucellosis.

Modelling the immunopathophysiology of Brucella melitensis and its lipopolysaccharide in mice infected via oral route of exposure

Brucella melitensis is one of the leading zoonotic pathogens with significant economic implications in animal industry worldwide. Lipopolysaccharide, however, remains by far the major virulence with substantial role in diseases pathogenesis. Nonetheless, the effect of B. melitensis and its lipopolysaccharide on immunopathophysiological aspects largely remains an enigma. This study examines the effect of B.melitensis and its lipopolysaccharide on immunopathophysiological parameters following experimental infection using mouse model. Eighty four (n = 84) mice, BALB/c, both sexes with equal gender distribution and 6-8 weeks-old were randomly assigned into three groups. Group 1-2 (n = 72) were orally inoculated with 0.4 mL containing 10⁹ CFU/mL of B. melitensis and its LPS, respectively. Group 3 (n = 12) was challenged orally with phosphate buffered saline and served as a control group. Animals were observed for clinical signs, haematological and histopathological analysis for a period of 24 days post-infection. We hereby report that B.melitensis infected group demonstrated significant clinical signs and histopathological changes than LPS infected group. However, both infected groups showed elevated levels of interleukins (IL-1β and IL-6) and antibody levels (IgM and IgG) with varying degrees of predominance in LPS infected group than B. melitensis infected group. For hormone analysis, low levels of progesterone, estradiol and testosterone were observed in both B. melitensis and LPS groups throughout the study period. Moreover, in B. melitensis infected group, the organism was re-isolated from the organs and tissues of gastrointestinal, respiratory and reproductive systems thereby confirming the infection and transmission dynamics. This report is the first detailed investigation comparing the infection progression and host responses in relation to the immunopathophysiological aspects in a mouse model after oral inoculation with B. melitensis and its lipopolysaccharide.

Genetic Diversity of Brucella melitensis in Kazakhstan in Relation to World-Wide Diversity

We describe the genetic diversity of 1327 Brucella strains from human patients in Kazakhstan using multiple-locus variable-number tandem repeat (VNTR) analysis (MLVA). All strains were assigned to the Brucella melitensis East Mediterranean group and clustered into 16 MLVA11 genotypes, nine of which are reported for the first time. MLVA11 genotype 116 predominates (86.8%) and is present all over Kazakhstan indicating existence and temporary preservation of a “founder effect” among B. melitensis strains circulating in Central Eurasia. The diversity pattern observed in humans is highly similar to the pattern previously reported in animals. The diversity observed by MLVA suggested that the epidemiological status of brucellosis in Kazakhstan is the result of the introduction of a few lineages, which have subsequently diversified at the most unstable tandem repeat loci. This investigation will allow to select the most relevant strains for testing these hypotheses via whole genome sequencing and to subsequently adjust the genotyping scheme to the Kazakhstan epidemiological situation.

The possible zoonotic diseases transferring from pig to human in Vietnam

Southeast Asia is considered one of worldwide hotspots consisting many distinct zoonotic infections. With optimal condition for the development of various pathogens, Vietnam is facing serious risks of zoonotic diseases. Besides, more than 50% Vietnamese people settle in rustic areas and earn their livings through small-scale animal breeding. It is possible that zoonotic diseases can be easily spread to the population by close contact with the infected animals, their infected residues, contaminated water, soil, or other possible means of transmission. In fact, zoonotic infections-transmissible infections between vertebrate animals and humans-cover a wide range of diseases with distinctive clinical and epidemiological highlights. With insufficient understanding and swift alteration in toxicity of the pathogens, these infections have gained more concerns due to sophisticated routes of transmission and harmful threats to humans. Recently emerging viral diseases exerted potential dangers to human beings, which required many countries to impose immediate actions to prevent any complications. Vietnam has recorded several cases of zoonotic diseases, especially pig-related illnesses; however, the studies on these diseases in this country remain limited. This work aims to highlight the zoonotic diseases transferring from pigs to humans and discuss risk factors of these diseases in Vietnam.

Identification of Cross-Protective Potential Antigens against Pathogenic Brucella spp. through Combining Pan-Genome Analysis with Reverse Vaccinology

Brucellosis is a zoonotic infectious disease caused by bacteria of the genus Brucella. Brucella melitensis, Brucella abortus, and Brucella suis are the most pathogenic species of this genus causing the majority of human and domestic animal brucellosis. There is a need to develop a safe and potent subunit vaccine to overcome the serious drawbacks of the live attenuated Brucella vaccines. The aim of this work was to discover antigen candidates conserved among the three pathogenic species. In this study, we employed a reverse vaccinology strategy to compute the core proteome of 90 completed genomes: 55 B. melitensis, 17 B. abortus, and 18 B. suis. The core proteome was analyzed by a metasubcellular localization prediction pipeline to identify surface-associated proteins. The identified proteins were thoroughly analyzed using various in silico tools to obtain the most potential protective antigens. The number of core proteins obtained from analyzing the 90 proteomes was 1939 proteins. The surface-associated proteins were 177. The number of potential antigens was 87; those with adhesion score ≥ 0.5 were considered antigen with "high potential," while those with a score of 0.4-0.5 were considered antigens with "intermediate potential." According to a cumulative score derived from protein antigenicity, density of MHC-I and MHC-II epitopes, MHC allele coverage, and B-cell epitope density scores, a final list of 34 potential antigens was obtained. Remarkably, most of the 34 proteins are associated with bacterial adhesion, invasion, evasion, and adaptation to the hostile intracellular environment of macrophages which is adjusted to deprive Brucella of required nutrients. Our results provide a manageable list of potential protective antigens for developing a potent vaccine against brucellosis. Moreover, our elaborated analysis can provide further insights into novel Brucella virulence factors. Our next step is to test some of these antigens using an appropriate antigen delivery system.

Comparative Genomics and in vitro Infection of Field Clonal Isolates of Brucella melitensis Biovar 3 Did Not Identify Signature of Host Adaptation

Brucella spp. are responsible for brucellosis, a widespread zoonosis causing reproductive disorders in animals. Species-classification within this monophyletic genus is based on bacteriological and biochemical phenotyping. Traditionally, Brucella species are reported to have a preferential, but not exclusive mammalian host. However, this concept can be challenged since many Brucella species infect a wide range of animal species. Adaptation to a specific host can be a driver of pathogen variation. It is generally thought that Brucella species have highly stable and conserved genomes, however the degree of genomic variation during natural infection has not been documented. Here, we investigated potential genetic diversity and virulence of Brucella melitensis biovar 3 field isolates obtained from a single outbreak but from different host species (human, bovine, small ruminants). A unique MLVA-16 pattern suggested all isolates were clonal. Comparative genomic analyses showed an almost non-existent genetic diversity among isolates (only one SNP; no architectural rearrangements) and did not highlight any signature specific to host adaptation. Similarly, the strains showed identical capacities to enter and replicate in an in vitro model of macrophage infection. In our study, the absence of genomic variability and similar virulence underline that B. melitensis biovar 3 is a broad-host-range pathogen without the need to adapt to different hosts.

Typing and comparative genome analysis of Brucella melitensis isolated from Lebanon

Brucella melitensis is the main causative agent of the zoonotic disease brucellosis. This study aimed at typing and characterizing genetic variation in 33 Brucella isolates recovered from patients in Lebanon. Bruce-ladder multiplex PCR and PCR-RFLP of omp31, omp2a and omp2b were performed. Sixteen representative isolates were chosen for draft-genome sequencing and analyzed to determine variations in virulence, resistance, genomic islands, prophages and insertion sequences. Comparative whole-genome single nucleotide polymorphism analysis was also performed. The isolates were confirmed to be B. melitensis. Genome analysis revealed multiple virulence determinants and efflux pumps. Genome comparisons and single nucleotide polymorphisms divided the isolates based on geographical distribution but revealed high levels of similarity between the strains. Sequence divergence in B. melitensis was mainly due to lateral gene transfer of mobile elements. This is the first report of an in-depth genomic characterization of B. melitensis in Lebanon.

Brucellosis: Evolution and expected comeback

Brucellosis is a serious infectious disease which causes great direct and indirect economic loses for animal holders worldwide such as the reduction of milk and meat production through abortions/culling of positive reactors, the expense of disease control/eradication and farmers compensation. Although the disease was eradicated from most of the industrial countries, it remains one of the most common zoonotic diseases in developing countries being responsible for more than 500,000 new cases yearly. Brucella is considered to be a bioterrorism organism due to its low infectious doses (10-100 bacteria), capability of persistence in the environment, rapid transmission via different routes including aerosols, and finally due to its difficult treatment by antibiotics.There are many reasons to believe that a new comeback of brucellosis may occur in near future. This expectation is supported by the recent discovery of new atypical Brucella species with new genetic properties and the recent reports of (man to man) disease transmission as will be discussed later. The development of new concepts and measurements for disease control is urgently required. In the present review, the evolution of Brucella and the different factors favoring its comeback are discussed.

Pangenomic Definition of Prokaryotic Species and the Phylogenetic Structure of Prochlorococcus spp

The pangenome is the collection of all groups of orthologous genes (OGGs) from a set of genomes. We apply the pangenome analysis to propose a definition of prokaryotic species based on identification of lineage-specific gene sets. While being similar to the classical biological definition based on allele flow, it does not rely on DNA similarity levels and does not require analysis of homologous recombination. Hence this definition is relatively objective and independent of arbitrary thresholds. A systematic analysis of 110 accepted species with the largest numbers of sequenced strains yields results largely consistent with the existing nomenclature. However, it has revealed that abundant marine cyanobacteria Prochlorococcus marinus should be divided into two species. As a control we have confirmed the paraphyletic origin of Yersinia pseudotuberculosis (with embedded, monophyletic Y. pestis) and Burkholderia pseudomallei (with B. mallei). We also demonstrate that by our definition and in accordance with recent studies Escherichia coli and Shigella spp. are one species.

Brucellosis Risk in Urban and Agro-pastoral Areas in Tanzania

Epidemiology of human and animal brucellosis may depend on ecological conditions. A cross-sectional study was conducted to compare prevalence and risk factors of bovine brucellosis, and risky behaviours for the human infection between urban and agro-pastoral areas in Morogoro region, Tanzania. Cattle blood sampling and interviews using a structured questionnaire were conducted with farmers. Rose-Bengal test was conducted for the cattle sera, and positive samples were confirmed with competitive ELISA. Farm-level sero-prevalences were 0.9% (1/106, 95% CI 0.0-5.9%) and 52.9% (9/17, 95% CI 28.5-76.1%) in urban and agro-pastoral areas, respectively. The animal-level-adjusted prevalences were 0.2% (1/667, 95% CI 0.0-1.1%) and 7.0% (28/673, 95% CI 5.7-8.4%) in those areas. The final farm-level model including both areas found two risk factors: history of abortion in the herd (P < 0.01) and cattle grazing (P = 0.07). The animal-level risk factors in agro-pastoral areas were age (P = 0.04) and history of abortion (P = 0.03). No agro-pastoral farmer knew about Brucella vaccine. Agro-pastoralists generally had poorer knowledge on brucellosis and practiced significantly more risky behaviours for human brucellosis such as drinking raw milk (17.6%, P < 0.01) and blood (35.3%, P < 0.01), and helping cattle birth (100%, P = 0.04) than urban farmers (0, 0 and 79.2%, respectively). Intervention programs through education including both human and animal health particularly targeting agro-pastoralists would be needed.

[Characterization of the genetic variability of field strains of Brucella canis isolated in Antioquia]

Brucella canis is a facultative intracellular pathogen responsible for canine brucellosis, a zoonotic disease that affects canines, causing abortions and reproductive failure; and the production of non-specific symptoms in humans. In 2005 the presence of B. canis in Antioquia was demonstrated and the strains were identified as type 2. The sequencing of the genome of a field strain denoted Brucella canis str. Oliveri, showed species-specific indel events, which led us to investigate the genomic characteristics of the B. canis strain isolated and to establish the phylogenetic relationships and the divergence time of B. canis str. Oliveri. Conventional PCR sequencing was performed in 30 field strains identifying 5 indel events recognized in B. canis str. Oliveri. ADN from Brucella suis, Brucella melitensis and vaccine strains from Brucella abortus were used as control, and it was determined that all of the studied field strains shared 4 out of the 5 indels of the sequenced Oliveri strain, indicating the presence of more than one strain circulating in the region. Phylogenetic analysis was performed with 24 strains of Brucella using concatenated sequences of genetic markers for species differentiation. The molecular clock hypothesis and Tajima's relative rate test were tested, showing that the Oliveri strain, similarly to other canis species, diverged from B. suis. The molecular clock hypothesis between Brucella species was rejected and an evolution rate and a similar genetic distance between the B. canis were demonstrated.

Identification of genetic variants of Brucella spp. through genome-wide association studies

Brucellosis is an important zoonotic disease caused by Brucella spp. We present a phylogeny of 552 strains based on genome-wide single nucleotide polymorphisms (SNPs) determined by an alignment-free k-mer approach. A total of 138,029 SNPs were identified from 552 Brucella genomes. Of these, 31,152 and 106,877 were core and non-core SNPs, respectively. Based on pan-genome analysis 11,937 and 972 genes were identified as pan and core genome, respectively. The pan-genome-wide analysis studies (Pan-GWAS) could not identify the group-specific variants in Brucella spp. Therefore, we focused on SNP based genome-wide association studies (SNP-GWAS) to identify the species-specific genetic determinants in Brucella spp. Phylogenetic tree representing eleven recognized Brucella spp. showed 16 major lineages. We identified 143 species-specific SNPs in Brucella abortus that are conserved in 311 B. abortus genomes. Of these, 141 species-specific SNPs were confined in the positively significant SNPs of B. abortus using SNP-GWAS. Since conserved in all the B. abortus genomes studied, these SNPs might have originated very early during the evolution of B. abortus and might be responsible for the evolution of B. abortus with cattle as the preferred host. Similarly, we identified 383 species-specific SNPs conserved in 132 Brucella melitensis genomes. Of these 379 species-specific SNPs were identified as positively associated using GWAS. Interestingly, >98% of the SNPs that are significantly, positively associated with the traits showed 100% sensitivity and 100% specificity. These identified species-specific core-SNPs identified in Brucella genomes could be responsible for the speciation and their respective host adaptation.

Evolution and genome specialization of Brucella suis biovar 2 Iberian lineages

Background

Swine brucellosis caused by B. suis biovar 2 is an emergent disease in domestic pigs in Europe. The emergence of this pathogen has been linked to the increase of extensive pig farms and the high density of infected wild boars (Sus scrofa). In Portugal and Spain, the majority of strains share specific molecular characteristics, which allowed establishing an Iberian clonal lineage. However, several strains isolated from wild boars in the North-East region of Spain are similar to strains isolated in different Central European countries.

Results

Comparative analysis of five newly fully sequenced B. suis biovar 2 strains belonging to the main circulating clones in Iberian Peninsula, with publicly available Brucella spp. genomes, revealed that strains from Iberian clonal lineage share 74% similarity with those reference genomes. Besides the 210 kb translocation event present in all biovar 2 strains, an inversion with 944 kb was presented in chromosome I of strains from the Iberian clone. At left and right crossover points, the inversion disrupted a TRAP dicarboxylate transporter, DctM subunit, and an integral membrane protein TerC. The gene dctM is well conserved in Brucella spp. except in strains from the Iberian clonal lineage. Intraspecies comparative analysis also exposed a number of biovar-, haplotype- and strain-specific insertion-deletion (INDELs) events and single nucleotide polymorphisms (SNPs) that could explain differences in virulence and host specificities. Most discriminative mutations were associated to membrane related molecules (29%) and enzymes involved in catabolism processes (20%). Molecular identification of both B. suis biovar 2 clonal lineages could be easily achieved using the target-PCR procedures established in this work for the evaluated INDELs.

Conclusion

Whole-genome analyses supports that the B. suis biovar 2 Iberian clonal lineage evolved from the Central-European lineage and suggests that the genomic specialization of this pathogen in the Iberian Peninsula is independent of a specific genomic event(s), but instead driven by allopatric speciation, resulting in the establishment of a new ecovar.

Electronic supplementary material

The online version of this article (10.1186/s12864-017-4113-8) contains supplementary material, which is available to authorized users.

Epidemiology and genetic characterization of BVDV, BHV-1, BHV-4, BHV-5 and Brucella spp. infections in cattle in Turkey

The aim of the study was to determine the epidemiological data of bovine viral diarrhea virus (BVDV), bovine herpesvirus-1 (BHV-1), bovine herpesvirus-4 (BHV-4), bovine herpesvirus-5 (BHV-5) and Brucella–associated cattle that were previously reported to have abortion and infertility problems in Ankara, Corum, Kirikkale and Yozgat provinces, Turkey. Whole blood and sera samples were obtained from 656 cattle, and antibodies against Brucella spp. were detected in 45 (6.86%) and 41 (6.25%) animals by Rose Bengal plate and serum tube agglutination tests, respectively. The seropositivity rates against BVDV, BHV-1 and BHV-4 were 70.89%, 41.3% and 28.78%, respectively. RT-PCR and PCR were performed to detect RNA and DNA viruses in blood samples, respectively. The BVDV 5′-untranslated region and BHV-1 gB gene detected in this study were phylogenetically analyzed. The BVDV strains analyzed in this study were closely related to those previously reported from Turkey. The nucleotide sequence from the BHV-1 strain detected in this study is the first nucleotide sequence of BHV-1 circulating in this area of Turkey deposited in the GenBank. The presence of Brucella spp. and prevalence of BHV-1, BHV-4 and BVDV in cattle should be further investigated throughout these regions.

A duplex PCR for rapid and simultaneous detection of Brucella spp. in human blood samples

OBJECTIVE

To design a duplex PCR for rapid and simultaneous detection of Brucella species. in human blood samples.

METHODS

Fifty-two peripheral bloods samples were collected from suspicious patients with brucellosis. Following DNA extraction, PCR assay were performed, using three primers that could simultaneously identify and differentiate three major species of pathogenic Brucella in humans and animals.

RESULTS

Of the 52 peripheral bloods samples tested, 25 sample (48%) showed positive reactions in PCR. Twelve samples were positive for Brucella abortus 39 (B. abortus 39) (23%), 13 for Brucella melitensis 39 (B. melitensis 39) (25%) and 0 for Brucella ovis 39 (B. ovis 39) (0%).

CONCLUSIONS

This work demonstrates that in case where specific primers were utilized, duplex PCR has proved to be a simple, fast, and relatively inexpensive method for simultaneous detection of important species of Brucella in clinical samples.

Brucella BioR regulator defines a complex regulatory mechanism for bacterial biotin metabolism

The enzyme cofactor biotin (vitamin H or B7) is an energetically expensive molecule whose de novo biosynthesis requires 20 ATP equivalents. It seems quite likely that diverse mechanisms have evolved to tightly regulate its biosynthesis. Unlike the model regulator BirA, a bifunctional biotin protein ligase with the capability of repressing the biotin biosynthetic pathway, BioR has been recently reported by us as an alternative machinery and a new type of GntR family transcriptional factor that can repress the expression of the bioBFDAZ operon in the plant pathogen Agrobacterium tumefaciens. However, quite unusually, a closely related human pathogen, Brucella melitensis, has four putative BioR-binding sites (both bioR and bioY possess one site in the promoter region, whereas the bioBFDAZ [bio] operon contains two tandem BioR boxes). This raised the question of whether BioR mediates the complex regulatory network of biotin metabolism. Here, we report that this is the case. The B. melitensis BioR ortholog was overexpressed and purified to homogeneity, and its solution structure was found to be dimeric. Functional complementation in a bioR isogenic mutant of A. tumefaciens elucidated that Brucella BioR is a functional repressor. Electrophoretic mobility shift assays demonstrated that the four predicted BioR sites of Brucella plus the BioR site of A. tumefaciens can all interact with the Brucella BioR protein. In a reporter strain that we developed on the basis of a double mutant of A. tumefaciens (the ΔbioR ΔbioBFDA mutant), the β-galactosidase (β-Gal) activity of three plasmid-borne transcriptional fusions (bioBbme-lacZ, bioYbme-lacZ, and bioRbme-lacZ) was dramatically decreased upon overexpression of Brucella bioR. Real-time quantitative PCR analyses showed that the expression of bioBFDA and bioY is significantly elevated upon removal of bioR from B. melitensis. Together, we conclude that Brucella BioR is not only a negative autoregulator but also a repressor of expression of bioY and bio operons that separately function in biotin transport and the biosynthesis pathway.

Draft Genome Sequence of Brucella abortus BCB027, a Strain Isolated from a Domestic Deer

Many Brucella species are isolated from nonpreferred hosts, and these bacteria may show genetic differences from isolates from the preferred hosts. Here, we report the draft genome sequence of Brucella abortus BCB027, a novel strain isolated from a domestic deer.

Complete genome sequence of Brucella abortus strain BCB034, a strain of biovar 2 isolated from human

Brucella abortus is divided into eight biovars, of which biovars 1 to 3 are the most frequently represented biovars in strains isolated from humans. Here, we report the genome sequence of B. abortus strain BCB034, a strain isolated from a human patient and that belongs to biovar 2.

Complete genome sequence of Brucella suis field strain BCB025 of sequence type ST22

Brucella is a genus of relatively conservative pathogenic bacteria. Brucella suis is the most diversified Brucella species. Strains of B. suis belong to different sequence types. Here, we report the genome sequence of B. suis strain BCB025, one isolate of the sequence type 22 epidemic in China.