Classification of Brucella spp. isolated from marine mammals by DNA polymorphism at the omp2 locus

[Zoonotic potential of brucellosis in marine mammals]

Introduction

Brucellosis in marine mammals (cetacean and pinnipeds) has emerged in a very significant way during the last two decades. Currently Brucella ceti and Brucella pinnipedialis are the two recognized species in marine mammals, but available information is still limited. Several genotypes have been identified, and studies on the relationship between sequence type (ST) and organ pathogenicity or tropism have indicated differences in pathogenesis between B. ceti sequences in cetaceans. The zoonotic potential of this disease is based on the identification of the main sources of introduction and spread of Brucella spp. in the marine environment as well as on the factors of exposure of marine mammals and humans to the bacteria.

Bibliographic review

This article is a bibliographical review on marine mammal brucellosis, including the features, sources and transmission modes of each Brucella species, as well as their potential pathogenicity in animals and humans.

Conclusion

Different genotypes of marine Brucella spp have been isolated from marine mammal species but without any evidence of pathology induced by these bacteria. Associated lesions are variable and include subcutaneous abscesses, meningo-encephalomyelitis, pneumonia, myocarditis, osteoarthritis, orchitis, endometritis, placentitis and abortion. The isolation of marine B. spp from marine mammal respiratory parasites associated to lung injury has raised the intriguing possibility that they may serve as a vector for the transmission of this bacterium.The severity of marine B. spp remains unknown due to the lack of an estimate of the prevalence of this disease in marine mammals. The number of suspected human cases is still very limited. However, by analogy with other germs of the genus Brucella responsible for abortion in ruminants and for a febrile and painful state in human beings, prevention measures are essential. The significant increase in the number of strandings coupled with a high seroprevalence in certain species of marine mammals must be considered for people in direct or indirect contact with these animals. Ongoing epidemiological monitoring combined with extensive post-mortem examinations (necropsy, bacteriology and sequencing) of all species of stranded marine mammals would deepen knowledge on the zoonotic potential of marine Brucella species.

New insights into the pathogenesis and transmission of Brucella pinnipedialis: systemic infection in two bottlenose dolphins (Tursiops truncatus)

IMPORTANCE

Brucella spp. are zoonotic pathogens that can affect both terrestrial and marine mammals. Brucella ceti has been identified in various cetacean species, but only one sequence type (ST27) has been reported in humans. However, it is important to conduct surveillance studies to better understand the impact of marine Brucella species on marine mammals, a typically understudied host group. Here, we describe a systemic infection by two related strains of Brucella pinnipedialis (ST25) in a couple of live-stranded bottlenose dolphins, with more severe lesions in the younger animal. Furthermore, B. pinnipedialis was first detected in milk from a female cetacean that stranded with its offspring. Our study reveals novel insights into the epidemiology and pathological consequences of B. pinnipedialis infections in cetaceans, emphasizing the crucial importance of ongoing surveillance and accurate diagnosis to understand the impact of this pathogen on marine mammal populations.

A Novel Arthropod Host of Brucellosis in the Arid Steppe Ecosystem

Brucellosis is a severe public health problem in the Inner Mongolia regions of China. The recent prevalence of brucellosis outbreaks may be attributed to an increase in the activity of ticks and other air-borne vectors. Dermacentor nuttalli (D. nuttalli) is a native tick species of Inner Mongolia; similar to other tick species, D. nuttalli carries a variety of pathogens that can be transmitted to a wide range of animals. In this study, we have investigated the potential of D. nuttalli in transmitting brucellosis. From 2015 to 2019, 2,256 ticks were collected from 23 different pastoral areas of Hulun Buir. Brucellosis pathogen was detected using DNA extracted from different developmental stages of ticks. Salivary gland and midgut tissue samples were used as templates to amplify Brucella Bscp31 gene (Brucella genus-specific gene) by using TaqMan Real-Time polymerase chain reaction (PCR). To detect the presence of Bscp31 protein, which is specific to Brucella spp., in the midgut and salivary gland tissues of D. nuttalli, Western blotting and immunofluorescence were performed. Additionally, Brucella spp. were isolated using a culture medium. Tick samples were identified as D. nuttalli. Different percentages of Brucella genus-specific genes could be found in the tick samples. From 2015 to 2019, the positivity rate for the detection of Bscp31 gene in D. nuttalli ranged from 0.00 to 87.80%, with the highest rate of 89.00%. In addition, Brucella genus-specific genes were successfully detected in the samples isolated from all the developmental stages and anatomical regions of ticks. Bscp31 protein was present in the midgut and salivary gland of D. nuttalli. Further, B. melitensis biotype 3 was isolated from eggs and engorged adults of D. nuttalli. These findings demonstrate that D. nuttalli is a potent, long-term carrier of Brucella spp. that can exhibit transovarial transmission potential, presenting D. nuttalli as a novel arthropod host for Brucella spp. This study, therefore, indicates the potential risk of transmission of brucellosis via tick bites among animals as well as human beings.

Pan-Proteomic Analysis and Elucidation of Protein Abundance among the Closely Related Brucella Species, Brucella abortus and Brucella melitensis

Brucellosis is a zoonotic infection caused by bacteria of the genus Brucella. The species, B. abortus and B. melitensis, major causative agents of human brucellosis, share remarkably similar genomes, but they differ in their natural hosts, phenotype, antigenic, immunogenic, proteomic and metabolomic properties. In the present study, label-free quantitative proteomic analysis was applied to investigate protein expression level differences. Type strains and field strains were each cultured six times, cells were harvested at a midlogarithmic growth phase and proteins were extracted. Following trypsin digestion, the peptides were desalted, separated by reverse-phase nanoLC, ionized using electrospray ionization and transferred into an linear trap quadrapole (LTQ) Orbitrap Velos mass spectrometer to record full scan MS spectra (m/z 300–1700) and tandem mass spectrometry (MS/MS) spectra of the 20 most intense ions. Database matching with the reference proteomes resulted in the identification of 826 proteins. The Cluster of Gene Ontologies of the identified proteins revealed differences in bimolecular transport and protein synthesis mechanisms between these two strains. Among several other proteins, antifreeze proteins, Omp10, superoxide dismutase and 30S ribosomal protein S14 were predicted as potential virulence factors among the proteins differentially expressed. All mass spectrometry data are available via ProteomeXchange with identifier PXD006348.

Omp2b Porin Alteration in the Course of Evolution of Brucella spp

The genus Brucella comprises major pathogenic species causing disease in livestock and humans, e.g. B. melitensis. In the past few years, the genus has been significantly expanded by the discovery of phylogenetically more distant lineages comprising strains from diverse wildlife animal species, including amphibians and fish. The strains represent several potential new species, with B. inopinata as solely named representative. Being genetically more distant between each other, relative to the “classical” Brucella species, they present distinct atypical phenotypes and surface antigens. Among surface protein antigens, the Omp2a and Omp2b porins display the highest diversity in the classical Brucella species. The genes coding for these proteins are closely linked in the Brucella genome and oriented in opposite directions. They share between 85 and 100% sequence identity depending on the Brucella species, biovar, or genotype. Only the omp2b gene copy has been shown to be expressed and genetic variation is extensively generated by gene conversion between the two copies. In this study, we analyzed the omp2 loci of the non-classical Brucella spp. Starting from two distinct ancestral genes, represented by Australian rodent strains and B. inopinata, a stepwise nucleotide reduction was observed in the omp2b gene copy. It consisted of a first reduction affecting the region encoding the surface L5 loop of the porin, previously shown to be critical in sugar permeability, followed by a nucleotide reduction in the surface L8 loop-encoding region. It resulted in a final omp2b gene size shared between two distinct clades of non-classical Brucella spp. (African bullfrog isolates) and the group of classical Brucella species. Further evolution led to complete homogenization of both omp2 gene copies in some Brucella species such as B. vulpis or B. papionis. The stepwise omp2b deletions seemed to be generated through recombination with the respective omp2a gene copy, presenting a conserved size among Brucella spp., and may involve short direct DNA repeats. Successive Omp2b porin alteration correlated with increasing porin permeability in the course of evolution of Brucella spp. They possibly have adapted their porin to survive environmental conditions encountered and to reach their final status as intracellular pathogen.

Establishment of a recombinase polymerase amplification (RPA) assay for the detection of Brucella spp. Infection

Brucellosis is a worldwide re-emerging zoonosis. It has an economic impact due to abortion and loss of fertility in livestock. In this study, Real-time recombinase polymerase amplification (RT-RPA-BP26) targeting Brucella spp. bp26 gene and Lateral flow dipstick (LFD-RPA-IS711) combined with SYBR- Green recombinase polymerase amplification (RPA) targeting insertion sequence IS711 region of Brucella spp. bp26 gene, was developed to detect Brucella spp. from different sample types in domestic animals. The sensitivity and specificity of the two developed RPAs were compared with real-time PCR, PCR, and Rose Bengal Plate Test (RBPT). The analytical sensitivity and detection limit of Real-time RPA and LFD RPA were four and six copies per reaction respectively. The detection of six colony forming units (CFU) of the bacteria-bearing construct with the target sequence was within 20 min at 40 °C for Real-time RPA and 37 °C for LFD RPA. The LFD RPA could work at temperatures between 30 and 35 °C and could be completed within 10–30 min. No significant differences were observed when comparing the results from Real-time RPA and LFD RPA to Real-time PCR and PCR. Both methods showed no cross reactivity with Chlamydia abortus, Toxoplasma gondii, Salmonella typhimurium, and Escherichia coli. In conclusion, RPA is a useful and convenient field and point of care test for brucellosis.

•

RPA essays have been developed for detection of Brucella spp.

•

Kappa analysis showed perfect agreement with RT-PCT Nd PCR.

Phenotypic and Molecular Characterization of Brucella microti-Like Bacteria From a Domestic Marsh Frog (Pelophylax ridibundus)

Several Brucella isolates have been described in wild-caught and "exotic" amphibians from various continents and identified as B. inopinata-like strains. On the basis of epidemiological investigations conducted in June 2017 in France in a farm producing domestic frogs (Pelophylax ridibundus) for human consumption of frog's legs, potentially pathogenic bacteria were isolated from adults showing lesions (joint and subcutaneous abscesses). The bacteria were initially misidentified as Ochrobactrum anthropi using a commercial identification system, prior to being identified as Brucella spp. by MALDI-TOF assay. Classical phenotypic identification confirmed the Brucella genus, but did not make it possible to conclude unequivocally on species determination. Conventional and innovative bacteriological and molecular methods concluded that the investigated strain was very close to B. microti species, and not B. inopinata-like strains, as expected. The methods included growth kinetic, antimicrobial susceptibility testing, RT-PCR, Bruce-Ladder, Suis-Ladder, RFLP-PCR, AMOS-ERY, MLVA-16, the ectoine system, 16S rRNA and recA sequence analyses, the LPS pattern, in silico MLST-21, comparative whole-genome analyses (including average nucleotide identity ANI and whole-genome SNP analysis) and HRM-PCR assays. Minor polyphasic discrepancies, especially phage lysis and A-dominant agglutination patterns, as well as, small molecular divergences suggest the investigated strain should be considered a B. microti-like strain, raising concerns about its environmental persistence and unknown animal pathogenic and zoonotic potential as for other B. microti strains described to date.

Study of serum bactericidal and splenic activity of Total-OMP- CagA combination from Brucella abortus and Helicobacter pylori in BALB/c mouse model

BACKGROUND

Brucella is a Gram-negative and facultative intracellular organism that causes brucellosis, a common zoonotic disease. Over 500,000 people are annually affected by brucellosis. Brucella is highly infectious through inhalation route; for this reason it is used for biological warfare aims. This study aimed to study the serum bactericidal and splenic activity of Total-OMP-r CagA immunogens from Brucella abortus and Helicobacter pylori in a BALB/c mouse model.

METHODS

Immunization of BALB/c mice was performed with immunogenic proteins three times subcutaneously (S.C.) at 14-day intervals. The protective effects of two component vaccines with CpG adjuvant were evaluated after mice were challenged with H. pylori ss1 and Brucella abortus strain 544. The specific IgG1 and IgG2a antibodies in sera were assessed using ELISA test. For measuring the antigen-specific IL-4, IL-12 and IFN-γ responses in sera of immunized mice after challenge, RT-PCR technique was applied. Twenty days after the challenge, mice were killed then gastric, splenic and serum samples were assessed and bacterial colony count was measured based on the pour plate count agar.

RESULTS

The results indicated that rCagA + OMP decreased bacterial colonization in these tissues, and significant difference was observed between test and control groups (p value˂0.001).

CONCLUSION

Our results showed that the combination vaccine was effective against an oral exposure and the bacterial burden in the spleen, serum and gastric tissues were reduced in mice immunized with the Total- OMP-CagA.

BRUCELLA PINNIPEDIALIS IN GREY SEALS ( HALICHOERUS GRYPUS) AND HARBOR SEALS ( PHOCA VITULINA) IN THE NETHERLANDS

Brucellosis is a zoonotic disease with terrestrial or marine wildlife animals as potential reservoirs for the disease in livestock and human populations. The primary aim of this study was to assess the presence of Brucella pinnipedialis in marine mammals living along the Dutch coast and to observe a possible correlation between the presence of B. pinnipedialis and accompanying pathology found in infected animals. The overall prevalence of Brucella spp. antibodies in sera from healthy wild grey seals ( Halichoerus grypus; n=11) and harbor seals ( Phoca vitulina; n=40), collected between 2007 and 2013 ranged from 25% to 43%. Additionally, tissue samples of harbor seals collected along the Dutch shores between 2009 and 2012, were tested for the presence of Brucella spp. In total, 77% (30/39) seals were found to be positive for Brucella by IS 711 real-time PCR in one or more tissue samples, including pulmonary nematodes. Viable Brucella was cultured from 40% (12/30) real-time PCR-positive seals, and was isolated from liver, lung, pulmonary lymph node, pulmonary nematode, or spleen, but not from any PCR-negative seals. Tissue samples from lung and pulmonary lymph nodes were the main source of viable Brucella bacteria. All isolates were typed as B. pinnipedialis by multiple-locus variable number of tandem repeats analysis-16 clustering and matrix-assisted laser desorption ionization-time of flight mass spectrometry, and of sequence type ST25 by multilocus sequence typing analysis. No correlation was observed between Brucella infection and pathology. This report displays the isolation and identification of B. pinnipedialis in marine mammals in the Dutch part of the Atlantic Ocean.

Main Groups of Microorganisms of Relevance for Food Safety and Stability

Microbiology is important to food safety, production, processing, preservation, and storage. Microbes such as bacteria, molds, and yeasts are employed for the foods production and food ingredients such as production of wine, beer, bakery, and dairy products. On the other hand, the growth and contamination of spoilage and pathogenic microorganisms is considered as one of the main causes to loss of foodstuff nowadays. Although technology, hygienic strategies, and traceability are important factors to prevent and delay microbial growth and contamination, food remains susceptible to spoilage and activity of pathogen microorganisms. Food loss by either spoilage or contaminated food affects food industry and consumers leading to economic losses and increased hospitalization costs. This chapter focuses on general aspects, characteristics, and importance of main microorganisms (bacteria, yeasts, molds, virus, and parasites) involved in food spoilage or contamination: known and recently discovered species; defects and alterations in foodstuff; most common food associated with each foodborne disease; resistance to thermal processing; occurrence in different countries; outbreaks; and associated symptoms.

Oral immunization of mice with Omp31-loaded N-trimethyl chitosan nanoparticles induces high protection against Brucella melitensis infection

Brucellosis is a group of closely associated zoonotic bacterial illnesses caused by members of the genus Brucella. B. melitensis Omp31 is a promising candidate for a subunit vaccine against brucellosis. This study surveyed the immunogenicity of Omp31 alone and with incomplete Freund’s adjuvant (Omp31-IFA) and N-trimethyl chitosan (TMC/Omp31) nanoparticles (NPs), as well as the effect of Omp31 immunization route on immunological responses and protection. After expression and purification, the recombinant Omp31 (rOmp31) was loaded onto TMC NPs by ionic gelation. The particle size, loading efficiency and in vitro release of the NPs were examined. Omp31-IFA was administered intraperitoneally, while TMC/Omp31 NPs were administered orally and intraperitoneally. According to the antibody subclasses and cytokine profile, intraperitoneal immunization by Omp31-IFA and TMC/Omp31 NPs induced T helper 1 (Th1) and Th1–Th2 immune responses, respectively. On the other hand, oral immunization with TMC/Omp31 NPs elicited a mixed Th1–Th17 immune response. Data obtained from the cell proliferation assay showed that vaccination with Omp31 stimulated a vigorous antigen-specific cell proliferative response, which could be further increased after oral immunization with TMC/Omp31 NPs. Vaccinated groups of mice when challenged with B. melitensis 16M were found to be significantly protected in the orally administered group in comparison with the intraperitoneally immunized mice. Results of this study indicated that the reason for high protection after oral vaccination can be via elicited Th17 response.

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.

Isolation of Brucella pinnipedialis from Grey Seals (Halichoerus grypus) in the Baltic Sea

Brucella infection in seals was reported for the first time in 1994 around the coast of Scotland. Since then, marine mammal Brucella infections were found to be widely distributed in the northern hemisphere. Two Brucella species affect marine mammals: Brucella pinnipedialis in pinnipeds and Brucella ceti in cetaceans. We examined the livers of Baltic grey seals (Halichoerus grypus) from the Finnish coast (n=122) hunted, found dead, or killed as by-catch in fishing gear in 2013-15 as part of population health monitoring. We detected B. pinnipedialis in the livers of three grey seals. The bacterium was isolated from livers displaying parasitic cholangitis. We also detected Brucella DNA in liver flukes (Pseudamphistomum truncatum) obtained from a Brucella-infected grey seal, suggesting that flukes might be possible vectors of this pathogen in the marine environment.

Brucella Genetic Variability in Wildlife Marine Mammals Populations Relates to Host Preference and Ocean Distribution

Intracellular bacterial pathogens probably arose when their ancestor adapted from a free-living environment to an intracellular one, leading to clonal bacteria with smaller genomes and less sources of genetic plasticity. Still, this plasticity is needed to respond to the challenges posed by the host. Members of the Brucella genus are facultative-extracellular intracellular bacteria responsible for causing brucellosis in a variety of mammals. The various species keep different host preferences, virulence, and zoonotic potential despite having 97-99% similarity at genome level. Here, we describe elements of genetic variation in Brucella ceti isolated from wildlife dolphins inhabiting the Pacific Ocean and the Mediterranean Sea. Comparison with isolates obtained from marine mammals from the Atlantic Ocean and the broader Brucella genus showed distinctive traits according to oceanic distribution and preferred host. Marine mammal isolates display genetic variability, represented by an important number of IS711 elements as well as specific IS711 and SNPs genomic distribution clustering patterns. Extensive pseudogenization was found among isolates from marine mammals as compared with terrestrial ones, causing degradation in pathways related to energy, transport of metabolites, and regulation/transcription. Brucella ceti isolates infecting particularly dolphin hosts, showed further degradation of metabolite transport pathways as well as pathways related to cell wall/membrane/envelope biogenesis and motility. Thus, gene loss through pseudogenization is a source of genetic variation in Brucella, which in turn, relates to adaptation to different hosts. This is relevant to understand the natural history of bacterial diseases, their zoonotic potential, and the impact of human interventions such as domestication.

Microbiological laboratory diagnostics of neglected zoonotic diseases (NZDs)

This review reports on laboratory diagnostic approaches for selected, highly pathogenic neglected zoonotic diseases, i.e. anthrax, bovine tuberculosis, brucellosis, echinococcosis, leishmaniasis, rabies, Taenia solium-associated diseases (neuro-/cysticercosis & taeniasis) and trypanosomiasis. Diagnostic options, including microscopy, culture, matrix-assisted laser-desorption-ionisation time-of-flight mass spectrometry, molecular approaches and serology are introduced. These procedures are critically discussed regarding their diagnostic reliability and state of evaluation. For rare diseases reliable evaluation data are scarce due to the rarity of samples. If bio-safety level 3 is required for cultural growth, but such high standards of laboratory infrastructure are not available, serological and molecular approaches from inactivated sample material might be alternatives. Multiple subsequent testing using various test platforms in a stepwise approach may improve sensitivity and specificity. Cheap and easy to use tests, usually called "rapid diagnostic tests" (RDTs) may impact disease control measures, but should not preclude developing countries from state of the art diagnostics.

Evidence of Brucella strain ST27 in bottlenose dolphin (Tursiops truncatus) in Europe

Marine mammal brucellosis has been known for more than 20 years, but recent work suggests it is more widespread than originally thought. Brucella (B.) pinnipedialis has been isolated from pinnipeds, while B. ceti strains have been associated with cetaceans. Here we report a Brucella strain isolated from multiple lymph nodes of one bottlenose dolphin (Tursiops truncatus) during routine examination of dolphin carcasses found in the Croatian part of the northern Adriatic Sea during the summer of 2015. Classical bacteriological biotyping, PCR-based techniques (single, multiplex, PCR-RFLP) and 16S rRNA DNA sequencing were used to identify Brucella spp. Multiple-locus variable number tandem repeat analysis of 16 loci and multilocus sequence typing of 9 loci were used for genotyping and species determination. The combination of bacteriological, molecular and genotyping techniques identified our strain as ST27, previously identified as a human pathogen. This report provides, to our knowledge, the first evidence of ST27 in the Adriatic Sea in particular and in European waters in general. The zoonotic nature of the strain and its presence in the Adriatic, which is inhabited by bottlenose dolphins, suggest that the strain may pose a significant threat to human health.

Molecular typing of Brucella species isolates from Human and livestock bloods in Isfahan province

Background:

Human brucellosis is caused by infection with certain species of the genus Brucella and is characterized by bacterial persistence and inflammation of many host tissues. Handling all live Brucella involves risk of laboratory infection and very strict biosafety rules must be observed. In order to avoid these disadvantages, method based on the PCR-RFLP shows excellent typeability, reproducibility, stability, and epidemiological concordance. The omp2 locus contains two gene copies (named omp2a and omp2b) coding for porin proteins and has been found particularly useful for molecular typing and identification of Brucella at the species, biovar, or strain level. This study is designed to evaluate the molecular epidemiology of Brucella spp from human and livestock in Isfahan province, central region of Iran in order to use the findings in efficient disease prevention programs.

Materials and Methods:

One hundred ninety blood samples were collected from human and cattle with active brucellosis and 40 aborted ewes fetuses were collected and genotyped using PCR-RFLP technique, DNA polymorphisms such as the restriction patterns of the PCR-amplified omp2a and omp2b genes.

Results:

The molecular characterization performed to assess the species and the biovar of the Brucella strains. Analysis of the 230 isolates examined in this study generated three unique RFLP profiles. One of the profiles was the most common being present in 134/180.

Conclusion:

Our findings confirm abundance of B. melitensis, particularly biovar 1 in human and sheep are identical but B. abortus biovar 3 as the etiological agent of cattle brucellosis most frequently isolated in the Isfahan area.

Brucella ceti infection in dolphins from the Western Mediterranean sea

BACKGROUND

Brucella ceti infections have been increasingly reported in cetaceans. Brucellosis in these animals is associated with meningoencephalitis, abortion, discospondylitis', subcutaneous abscesses, endometritis and other pathological conditions B. ceti infections have been frequently described in dolphins from both, the Atlantic and Pacific Oceans. In the Mediterranean Sea, only two reports have been made: one from the Italian Tyrrhenian Sea and the other from the Adriatic Sea.

RESULTS

We describe the clinical and pathological features of three cases of B. ceti infections in three dolphins stranded in the Mediterranean Catalonian coast. One striped dolphin had neurobrucellosis, showing lethargy, incoordination and lateral swimming due to meningoencephalitis, A B. ceti infected bottlenose dolphin had discospondylitis, and another striped dolphin did not show clinical signs or lesions related to Brucella infection. A detailed characterization of the three B. ceti isolates was performed by bacteriological, molecular, protein and fatty acid analyses.

CONCLUSIONS

All the B. ceti strains originating from Mediterranean dolphins cluster together in a distinct phylogenetic clade, close to that formed by B. ceti isolates from dolphins inhabiting the Atlantic Ocean. Our study confirms the severity of pathological signs in stranded dolphins and the relevance of B. ceti as a pathogen in the Mediterranean Sea.

Enzymatic activity analysis and catalytic essential residues identification of Brucella abortus malate dehydrogenase

Malate dehydrogenase (MDH) plays important metabolic roles in bacteria. In this study, the recombinant MDH protein (His-MDH) of Brucella abortus was purified and its ability to catalyze the conversion of oxaloacetate (OAA) to L-malate (hereon referred to as MDH activity) was analyzed. Michaelis Constant (K_m) and Maximum Reaction Velocity (V_max) of the reaction were determined to be 6.45 × 10⁻³ M and 0.87 mM L⁻¹min⁻¹, respectively. In vitro studies showed that His-MDH exhibited maximal MDH activity in pH 6.0 reaction buffer at 40°C. The enzymatic activity was 100%, 60%, and 40% inhibited by Cu²⁺, Zn²⁺, and Pb²⁺, respectively. In addition, six amino acids in the MDH were mutated to investigate their roles in the enzymatic activity. The results showed that the substitutions of amino acids Arg 89, Asp 149, Arg 152, His 176, or Thr 231 almost abolished the activity of His-MDH. The present study will help to understand MDH's roles in B. abortus metabolism.

Characterization of the immunogenicity and pathogenicity of malate dehydrogenase in Brucella abortus

Brucella abortus is a gram-negative, facultative intracellular pathogen that causes brucellosis, a chronic zoonotic disease resulting in abortion in pregnant cattle and undulant fever in humans. Malate dehydrogenase (MDH), a key enzyme in the tricarboxylic acid cycle, plays important metabolic roles in aerobic energy producing pathways and in malate shuttle. In this study, the MDH-encoding gene for malate dehydrogenase mdh of B. abortus S2308 was cloned, sequenced and expressed. Western blot analysis demonstrated that MDH is an immunogenic membrane-associated protein. In addition, recombinant MDH showed sero-reactivity with 30 individual bovine B. abortus-positive sera by enzyme-linked immunosorbent assay, indicates that MDH may be used as a candidate marker for sero-diagnosis of brucellosis. Furthermore, MDH exhibits fibronectin and plasminogen-binding ability in immunoblotting assay. Inhibition assays on HeLa cells demonstrated that rabbit anti-serum against MDH significantly reduced both bacterial adherence and invasion abilities (p < 0.05), suggesting that MDH play a role in B. abortus colonization. Our results indicated that MDH is not only an immunogenic protein, but is also related to bacterial pathogenesis and may act as a new virulent factor, which will benefit for further understanding the MDH's roles in B. abortus metabolism, pathogenesis and immunity.

Brucella ceti from two striped dolphins stranded on the Apulia coastline, Italy

Since 1994, when Brucella ceti was first isolated from an aborted dolphin fetus, several cases have been reported worldwide. The first case of B. ceti in the Mediterranean (and in Italy), however, was recorded only in 2012, off the coast of Tuscany. Extensive studies, using serological and microbiological methods, have documented this bacterium in dolphins and demonstrated its zoonotic potential. We describe the typing of two B. ceti strains isolated from striped dolphins (Stenella coeruleoalba) stranded on the southern Apulia coastline. B. ceti isolates were conventionally typed, and then genotyped by both the multilocus sequence typing (MLST) and the multilocus variable number of tandem repeats typing (MLVA) methodologies to infer phylogeny and potential epidemiological links between the two cases. The two isolates were identified through MLST analysis as belonging to the common sequence type 26 (ST26), while MLVA analysis, having established that the two isolates have identical profiles, assigned them to a novel genotype within cluster A - a unique representative of a new Mediterranean subcluster. The results thus revealed a link between the two cases studied, demonstrating the usefulness of MLST and MLVA for the epidemiological investigation of brucellae among marine mammals.

What caused the UK's largest common dolphin (Delphinus delphis) mass stranding event?

On 9 June 2008, the UK's largest mass stranding event (MSE) of short-beaked common dolphins (Delphinus delphis) occurred in Falmouth Bay, Cornwall. At least 26 dolphins died, and a similar number was refloated/herded back to sea. On necropsy, all dolphins were in good nutritive status with empty stomachs and no evidence of known infectious disease or acute physical injury. Auditory tissues were grossly normal (26/26) but had microscopic haemorrhages (5/5) and mild otitis media (1/5) in the freshest cases. Five lactating adult dolphins, one immature male, and one immature female tested were free of harmful algal toxins and had low chemical pollutant levels. Pathological evidence of mud/seawater inhalation (11/26), local tide cycle, and the relative lack of renal myoglobinuria (26/26) suggested MSE onset on a rising tide between 06:30 and 08∶21 hrs (9 June). Potential causes excluded or considered highly unlikely included infectious disease, gas/fat embolism, boat strike, by-catch, predator attack, foraging unusually close to shore, chemical or algal toxin exposure, abnormal weather/climatic conditions, and high-intensity acoustic inputs from seismic airgun arrays or natural sources (e.g., earthquakes). International naval exercises did occur in close proximity to the MSE with the most intense part of the exercises (including mid-frequency sonars) occurring four days before the MSE and resuming with helicopter exercises on the morning of the MSE. The MSE may therefore have been a "two-stage process" where a group of normally pelagic dolphins entered Falmouth Bay and, after 3-4 days in/around the Bay, a second acoustic/disturbance event occurred causing them to strand en masse. This spatial and temporal association with the MSE, previous associations between naval activities and cetacean MSEs, and an absence of other identifiable factors known to cause cetacean MSEs, indicates naval activity to be the most probable cause of the Falmouth Bay MSE.

Internal affairs: investigating the Brucella intracellular lifestyle

Bacteria of the genus Brucella are Gram-negative pathogens of several animal species that cause a zoonotic disease in humans known as brucellosis or Malta fever. Within their hosts, brucellae reside within different cell types where they establish a replicative niche and remain protected from the immune response. The aim of this article is to discuss recent advances in the field in the specific context of the Brucella intracellular 'lifestyle'. We initially discuss the different host cell targets and their relevance during infection. As it represents the key to intracellular replication, the focus is then set on the maturation of the Brucella phagosome, with particular emphasis on the Brucella factors that are directly implicated in intracellular trafficking and modulation of host cell signalling pathways. Recent data on the role of the type IV secretion system are discussed, novel effector molecules identified and how some of them impact on trafficking events. Current knowledge on Brucella gene regulation and control of host cell death are summarized, as they directly affect intracellular persistence. Understanding how Brucella molecules interplay with their host cell targets to modulate cellular functions and establish the intracellular niche will help unravel how this pathogen causes disease.

Brucella ceti and brucellosis in cetaceans

Since the first case of brucellosis detected in a dolphin aborted fetus, an increasing number of Brucella ceti isolates has been reported in members of the two suborders of cetaceans: Mysticeti and Odontoceti. Serological surveys have shown that cetacean brucellosis may be distributed worldwide in the oceans. Although all B. ceti isolates have been included within the same species, three different groups have been recognized according to their preferred host, bacteriological properties, and distinct genetic traits: B. ceti dolphin type, B. ceti porpoise type, and B. ceti human type. It seems that B. ceti porpoise type is more closely related to B. ceti human isolates and B. pinnipedialis group, while B. ceti dolphin type seems ancestral to them. Based on comparative phylogenetic analysis, it is feasible that the B. ceti ancestor radiated in a terrestrial artiodactyl host close to the Raoellidae family about 58 million years ago. The more likely mode of transmission of B. ceti seems to be through sexual intercourse, maternal feeding, aborted fetuses, placental tissues, vertical transmission from mother to the fetus or through fish or helminth reservoirs. The B. ceti dolphin and porpoise types seem to display variable virulence in land animal models and low infectivity for humans. However, brucellosis in some dolphins and porpoises has been demonstrated to be a severe chronic disease, displaying significant clinical and pathological signs related to abortions, male infertility, neurobrucellosis, cardiopathies, bone and skin lesions, strandings, and death.

Intraspecies biodiversity of the genetically homologous species Brucella microti

Brucellosis is one of the major bacterial zoonoses worldwide. In the past decade, an increasing number of atypical Brucella strains and species have been described. Brucella microti in particular has attracted attention, because this species not only infects mammalian hosts but also persists in soil. An environmental reservoir may pose a new public health risk, leading to the reemergence of brucellosis. In a polyphasic approach, comprising conventional microbiological techniques and extensive biochemical and molecular techniques, all currently available Brucella microti strains were characterized. While differing in their natural habitats and host preferences, B. microti isolates were found to possess identical 16S rRNA, recA, omp2a, and omp2b gene sequences and identical multilocus sequence analysis (MLSA) profiles at 21 different genomic loci. Only highly variable microsatellite markers of multiple-locus variable-number tandem repeat (VNTR) analysis comprising 16 loci (MLVA-16) showed intraspecies discriminatory power. In contrast, biotyping demonstrated striking differences within the genetically homologous species. The majority of the mammalian isolates agglutinated only with monospecific anti-M serum, whereas soil isolates agglutinated with anti-A, anti-M, and anti-R sera. Bacteria isolated from animal sources were lysed by phages F1, F25, Tb, BK2, Iz, and Wb, whereas soil isolates usually were not. Rough strains of environmental origin were lysed only by phage R/C. B. microti exhibited high metabolic activities similar to those of closely related soil organisms, such as Ochrobactrum spp. Each strain was tested with 93 different substrates and showed an individual metabolic profile. In summary, the adaptation of Brucella microti to a specific habitat or host seems to be a matter of gene regulation rather than a matter of gene configuration.

Reliable identification at the species level of Brucella isolates with MALDI-TOF-MS

Background

The genus Brucella contains highly infectious species that are classified as biological threat agents. The timely detection and identification of the microorganism involved is essential for an effective response not only to biological warfare attacks but also to natural outbreaks. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) is a rapid method for the analysis of biological samples. The advantages of this method, compared to conventional techniques, are rapidity, cost-effectiveness, accuracy and suitability for the high-throughput identification of bacteria. Discrepancies between taxonomy and genetic relatedness on the species and biovar level complicate the development of detection and identification assays.

Results

In this study, the accurate identification of Brucella species using MALDI-TOF-MS was achieved by constructing a Brucella reference library based on multilocus variable-number tandem repeat analysis (MLVA) data. By comparing MS-spectra from Brucella species against a custom-made MALDI-TOF-MS reference library, MALDI-TOF-MS could be used as a rapid identification method for Brucella species. In this way, 99.3% of the 152 isolates tested were identified at the species level, and B. suis biovar 1 and 2 were identified at the level of their biovar. This result demonstrates that for Brucella, even minimal genomic differences between these serovars translate to specific proteomic differences.

Conclusions

MALDI-TOF-MS can be developed into a fast and reliable identification method for genetically highly related species when potential taxonomic and genetic inconsistencies are taken into consideration during the generation of the reference library.

Brucellosis Ontology (IDOBRU) as an extension of the Infectious Disease Ontology

Background

Caused by intracellular Gram-negative bacteria Brucella spp., brucellosis is the most common bacterial zoonotic disease. Extensive studies in brucellosis have yielded a large number of publications and data covering various topics ranging from basic Brucella genetic study to vaccine clinical trials. To support data interoperability and reasoning, a community-based brucellosis-specific biomedical ontology is needed.

Results

The Brucellosis Ontology (IDOBRU: http://sourceforge.net/projects/idobru), a biomedical ontology in the brucellosis domain, is an extension ontology of the core Infectious Disease Ontology (IDO-core) and follows OBO Foundry principles. Currently IDOBRU contains 1503 ontology terms, which includes 739 Brucella-specific terms, 414 IDO-core terms, and 350 terms imported from 10 existing ontologies. IDOBRU has been used to model different aspects of brucellosis, including host infection, zoonotic disease transmission, symptoms, virulence factors and pathogenesis, diagnosis, intentional release, vaccine prevention, and treatment. Case studies are typically used in our IDOBRU modeling. For example, diurnal temperature variation in Brucella patients, a Brucella-specific PCR method, and a WHO-recommended brucellosis treatment were selected as use cases to model brucellosis symptom, diagnosis, and treatment, respectively. Developed using OWL, IDOBRU supports OWL-based ontological reasoning. For example, by performing a Description Logic (DL) query in the OWL editor Protégé 4 or a SPARQL query in an IDOBRU SPARQL server, a check of Brucella virulence factors showed that eight of them are known protective antigens based on the biological knowledge captured within the ontology.

Conclusions

IDOBRU is the first reported bacterial infectious disease ontology developed to represent different disease aspects in a formal logical format. It serves as a brucellosis knowledgebase and supports brucellosis data integration and automated reasoning.

Novel IS711 chromosomal location useful for identification of marine mammal Brucella genotype ST27, which is associated with zoonotic infection

We report a novel IS711 chromosomal location that is specific for the Brucella genotype ST27 previously associated with Pacific marine mammals and human zoonotic infection in New Zealand and Peru. Our data support the previous observation that this peculiar genotype is distinct from those commonly isolated from the Atlantic and currently classified within the species B. ceti and B. pinnipedialis.

A review of Brucella infection in marine mammals, with special emphasis on Brucella pinnipedialis in the hooded seal (Cystophora cristata)

Brucella spp. were isolated from marine mammals for the first time in 1994. Two novel species were later included in the genus; Brucella ceti and Brucella pinnipedialis, with cetaceans and seals as their preferred hosts, respectively. Brucella spp. have since been isolated from a variety of marine mammals. Pathological changes, including lesions of the reproductive organs and associated abortions, have only been registered in cetaceans. The zoonotic potential differs among the marine mammal Brucella strains. Many techniques, both classical typing and molecular microbiology, have been utilised for characterisation of the marine mammal Brucella spp. and the change from the band-based approaches to the sequence-based approaches has greatly increased our knowledge about these strains. Several clusters have been identified within the B. ceti and B. pinnipedialis species, and multiple studies have shown that the hooded seal isolates differ from other pinniped isolates. We describe how different molecular methods have contributed to species identification and differentiation of B. ceti and B. pinnipedialis, with special emphasis on the hooded seal isolates. We further discuss the potential role of B. pinnipedialis for the declining Northwest Atlantic hooded seal population.

Identification of new IS711 insertion sites in Brucella abortus field isolates

BACKGROUND

Brucellosis is a zoonosis caused by Brucella spp., a group of highly homogeneous bacteria. The insertion sequence IS711 is characteristic of these bacteria, and occurs in variable numbers and positions, but always constant within a given species. This species-associated polymorphism is used in molecular typing and identification. Field isolates of B. abortus, the most common species infecting cattle, typically carry seven IS711 copies (one truncated). Thus far, IS711 transposition has only been shown in vitro and only for B. ovis and B. pinnipedialis, two species carrying a high number of IS711 copies, but never in other Brucella species, neither in vitro nor in field strains.

RESULTS

We found several B. abortus strains isolated from milk and aborted fetuses that carried additional IS711 copies in two hitherto undescribed insertion sites: one in an intergenic region near to the 3' end of a putative lactate permease gene and the other interrupting the sequence of a marR transcriptional regulator gene. Interestingly, the second type of insertion was identified in isolates obtained repeatedly from the same herd after successive brucellosis outbreaks, an observation that proves the stability and virulence of the new genotype under natural conditions. Sequence analyses revealed that the new copies probably resulted from the transposition of a single IS711 copy common to all Brucella species sequenced so far.

CONCLUSIONS

Our results show that the replicative transposition of IS711 can occur under field conditions. Therefore, it represents an active mechanism for the emergence of genetic diversity in B. abortus thus contributing to intra-species genetic polymorphism.

The genome sequence of Brucella pinnipedialis B2/94 sheds light on the evolutionary history of the genus Brucella

Background

Since the discovery of the Malta fever agent, Brucella melitensis, in the 19th century, six terrestrial mammal-associated Brucella species were recognized over the next century. More recently the number of novel Brucella species has increased and among them, isolation of species B. pinnipedialis and B. ceti from marine mammals raised many questions about their origin as well as on the evolutionary history of the whole genus.

Results

We report here on the first complete genome sequence of a Brucella strain isolated from marine mammals, Brucella pinnipedialis strain B2/94. A whole gene-based phylogenetic analysis shows that five main groups of host-associated Brucella species rapidly diverged from a likely free-living ancestor close to the recently isolated B. microti. However, this tree lacks the resolution required to resolve the order of divergence of those groups. Comparative analyses focusing on a) genome segments unshared between B. microti and B. pinnipedialis, b) gene deletion/fusion events and c) positions and numbers of Brucella specific IS711 elements in the available Brucella genomes provided enough information to propose a branching order for those five groups.

Conclusions

In this study, it appears that the closest relatives of marine mammal Brucella sp. are B. ovis and Brucella sp. NVSL 07-0026 isolated from a baboon, followed by B. melitensis and B. abortus strains, and finally the group consisting of B. suis strains, including B. canis and the group consisting of the single B. neotomae species. We were not able, however, to resolve the order of divergence of the two latter groups.

Infection with Brucella ceti and high levels of polychlorinated biphenyls in bottlenose dolphins (Tursiops truncatus) stranded in south-west England

Eight bottlenose dolphins (Tursiops truncatus) that stranded in Cornwall, south-west England, between June 2004 and December 2007 were examined using standardised postmortem examination and bacteriological methods. Evidence of Brucella species infection was found in four of these dolphins on culture. In addition, of the eight dolphins, four were positive and two were weakly positive for antibodies to Brucella species on serological analyses of pericardial and other fluids using a competitive ELISA and two indirect ELISAs. High or very high levels of the sum of 25 individual chlorobiphenyl congeners (∑25CBs) were also determined in blubber samples from two of the dolphins (45.5 and 446.6 mg/kg lipid weight).

Review of detection of Brucella spp. by polymerase chain reaction

Here we present a review of most of the currently used polymerase chain reaction (PCR)-based methods for identification of Brucella bacteria in biological samples. We focused in particular on methods using single-pair primers, multiplex primers, real-time PCRs, PCRs for marine Brucella, and PCRs for molecular biotyping. These methods are becoming very important tools for the identification of Brucella, at the species level and recently also at the biovar level. These techniques require minimum biological containment and can provide results in a very short time. In addition, genetic fingerprinting of isolates aid in epidemiological studies of the disease and its control. PCR-based methods are more useful and practical than conventional methods used to identify Brucella spp., and new methods for Brucella spp. identification and typing are still being developed. However, the sensitivity, specificity, and issues of quality control and quality assurance using these methods must be fully validated on clinical samples before PCR can be used in routine laboratory testing for brucellosis.

Development, validation, and utilization of a competitive enzyme-linked immunosorbent assay for the detection of antibodies against Brucella species in marine mammals

A competitive enzyme-linked immunosorbent assay (cELISA) was developed by using a whole-cell antigen from a marine Brucella sp. isolated from a harbor seal (Phoca vitulina). The assay was designed to screen sera from multiple marine mammal species for the presence of antibodies against marine-origin Brucella. Based on comparisons with culture-confirmed cases, specificity and sensitivity for cetacean samples tested were 73% and 100%, respectively. For pinniped samples, specificity and sensitivity values were 77% and 67%, respectively. Hawaiian monk seal (Monachus schauinslandi; n  =  28) and bottlenose dolphin (Tursiops truncatus; n  =  48) serum samples were tested, and the results were compared with several other assays designed to detect Brucella abortus antibodies. The comparison testing revealed the marine-origin cELISA to be more sensitive than the B. abortus tests by the detection of additional positive serum samples. The newly developed cELISA is an effective serologic method for detection of the presence of antibodies against marine-origin Brucella sp. in marine mammals.

Bioinformatics analysis of Brucella vaccines and vaccine targets using VIOLIN

BACKGROUND

Brucella spp. are Gram-negative, facultative intracellular bacteria that cause brucellosis, one of the commonest zoonotic diseases found worldwide in humans and a variety of animal species. While several animal vaccines are available, there is no effective and safe vaccine for prevention of brucellosis in humans. VIOLIN (http://www.violinet.org) is a web-based vaccine database and analysis system that curates, stores, and analyzes published data of commercialized vaccines, and vaccines in clinical trials or in research. VIOLIN contains information for 454 vaccines or vaccine candidates for 73 pathogens. VIOLIN also contains many bioinformatics tools for vaccine data analysis, data integration, and vaccine target prediction. To demonstrate the applicability of VIOLIN for vaccine research, VIOLIN was used for bioinformatics analysis of existing Brucella vaccines and prediction of new Brucella vaccine targets.

RESULTS

VIOLIN contains many literature mining programs (e.g., Vaxmesh) that provide in-depth analysis of Brucella vaccine literature. As a result of manual literature curation, VIOLIN contains information for 38 Brucella vaccines or vaccine candidates, 14 protective Brucella antigens, and 68 host response studies to Brucella vaccines from 97 peer-reviewed articles. These Brucella vaccines are classified in the Vaccine Ontology (VO) system and used for different ontological applications. The web-based VIOLIN vaccine target prediction program Vaxign was used to predict new Brucella vaccine targets. Vaxign identified 14 outer membrane proteins that are conserved in six virulent strains from B. abortus, B. melitensis, and B. suis that are pathogenic in humans. Of the 14 membrane proteins, two proteins (Omp2b and Omp31-1) are not present in B. ovis, a Brucella species that is not pathogenic in humans. Brucella vaccine data stored in VIOLIN were compared and analyzed using the VIOLIN query system.

CONCLUSIONS

Bioinformatics curation and ontological representation of Brucella vaccines promotes classification and analysis of existing Brucella vaccines and vaccine candidates. Computational prediction of Brucella vaccine targets provides more candidates for rational vaccine development. The use of VIOLIN provides a general approach that can be applied for analyses of vaccines against other pathogens and infection diseases.

Novel IS711-specific chromosomal locations useful for identification and classification of marine mammal Brucella strains

We report five new IS711 chromosomal locations that are specific for marine mammal Brucella groups of strains and useful for their identification and classification. Our data support their current classification into two species, Brucella ceti and B. pinnipedialis, with subgroups in each, but also the possibility of additional species.

Proteomics-based confirmation of protein expression and correction of annotation errors in the Brucella abortus genome

Background

Brucellosis is a major bacterial zoonosis affecting domestic livestock and wild mammals, as well as humans around the globe. While conducting proteomics studies to better understand Brucella abortus virulence, we consolidated the proteomic data collected and compared it to publically available genomic data.

Results

The proteomic data was compiled from several independent comparative studies of Brucella abortus that used either outer membrane blebs, cytosols, or whole bacteria grown in media, as well as intracellular bacteria recovered at different times following macrophage infection. We identified a total of 621 bacterial proteins that were differentially expressed in a condition-specific manner. For 305 of these proteins we provide the first experimental evidence of their expression. Using a custom-built protein sequence database, we uncovered 7 annotation errors. We provide experimental evidence of expression of 5 genes that were originally annotated as non-expressed pseudogenes, as well as start site annotation errors for 2 other genes.

Conclusions

An essential element for ensuring correct functional studies is the correspondence between reported genome sequences and subsequent proteomics studies. In this study, we have used proteomics evidence to confirm expression of multiple proteins previously considered to be putative, as well as correct annotation errors in the genome of Brucella abortus strain 2308.

Identification of an unusual Brucella strain (BO2) from a lung biopsy in a 52 year-old patient with chronic destructive pneumonia

Background

Brucellosis is primarily a zoonotic disease caused by Brucella species. There are currently ten Brucella spp. including the recently identified novel B. inopinata sp. isolated from a wound associated with a breast implant infection. In this study we report on the identification of an unusual Brucella-like strain (BO2) isolated from a lung biopsy in a 52-year-old patient in Australia with a clinical history of chronic destructive pneumonia.

Results

Standard biochemical profiles confirmed that the unusual strain was a member of the Brucella genus and the full-length 16S rRNA gene sequence was 100% identical to the recently identified B. inopinata sp. nov. (type strain BO1^T). Additional sequence analysis of the recA, omp2a and 2b genes; and multiple locus sequence analysis (MLSA) demonstrated that strain BO2 exhibited significant similarity to the B. inopinata sp. compared to any of the other Brucella or Ochrobactrum species. Genotyping based on multiple-locus variable-number tandem repeat analysis (MLVA) established that the BO2 and BO1^Tstrains form a distinct phylogenetic cluster separate from the other Brucella spp.

Conclusion

Based on these molecular and microbiological characterizations, we propose that the BO2 strain is a novel lineage of the newly described B. inopinata species.

MLVA-16 typing of 295 marine mammal Brucella isolates from different animal and geographic origins identifies 7 major groups within Brucella ceti and Brucella pinnipedialis

Background

Since 1994, Brucella strains have been isolated from a wide range of marine mammals. They are currently recognized as two new Brucella species, B. pinnipedialis for the pinniped isolates and B. ceti for the cetacean isolates in agreement with host preference and specific phenotypic and molecular markers. In order to investigate the genetic relationships within the marine mammal Brucella isolates and with reference to terrestrial mammal Brucella isolates, we applied in this study the Multiple Loci VNTR (Variable Number of Tandem Repeats) Analysis (MLVA) approach. A previously published assay comprising 16 loci (MLVA-16) that has been shown to be highly relevant and efficient for typing and clustering Brucella strains from animal and human origin was used.

Results

294 marine mammal Brucella strains collected in European waters from 173 animals and a human isolate from New Zealand presumably from marine origin were investigated by MLVA-16. Marine mammal Brucella isolates were shown to be different from the recognized terrestrial mammal Brucella species and biovars and corresponded to 3 major related groups, one specific of the B. ceti strains, one of the B. pinnipedialis strains and the last composed of the human isolate. In the B. ceti group, 3 subclusters were identified, distinguishing a cluster of dolphin, minke whale and porpoise isolates and two clusters mostly composed of dolphin isolates. These results were in accordance with published analyses using other phenotypic or molecular approaches, or different panels of VNTR loci. The B. pinnipedialis group could be similarly subdivided in 3 subclusters, one composed exclusively of isolates from hooded seals (Cystophora cristata) and the two others comprising other seal species isolates.

Conclusion

The clustering analysis of a large collection of marine mammal Brucella isolates from European waters significantly strengthens the current view of the population structure of these two species, and their relative position with respect to the rest of the Brucella genus. MLVA-16 is confirmed as being a rapid, highly discriminatory and reproducible method to classify Brucella strains including the marine mammal isolates. The Brucella2009 MLVA-16 genotyping database available at http://mlva.u-psud.fr/ is providing a detailed coverage of all 9 currently recognized Brucella species.

DNA polymorphism analysis of Brucella lipopolysaccharide genes reveals marked differences in O-polysaccharide biosynthetic genes between smooth and rough Brucella species and novel species-specific markers

Background

The lipopolysaccharide is a major antigen and virulence factor of Brucella, an important bacterial pathogen. In smooth brucellae, lipopolysaccharide is made of lipid A-core oligosaccharide and N-formylperosamine O-polysaccharide. B. ovis and B. canis (rough species) lack the O-polysaccharide.

Results

The polymorphism of O-polysaccharide genes wbkE, manA_O-Ag, manB_O-Ag, manC_O-Ag, wbkF and wbkD) and wbo (wboA and wboB), and core genes manB_core and wa** was analyzed. Although most genes were highly conserved, species- and biovar-specific restriction patterns were found. There were no significant differences in putative N-formylperosamyl transferase genes, suggesting that Brucella A and M serotypes are not related to specific genes. In B. pinnipedialis and B. ceti (both smooth), manB_O-Ag carried an IS711, confirming its dispensability for perosamine synthesis. Significant differences between smooth and rough species were found in wbkF and wbkD, two adjacent genes putatively related to bactoprenol priming for O-polysaccharide polymerization. B. ovis wbkF carried a frame-shift and B. canis had a long deletion partially encompassing both genes. In smooth brucellae, this region contains two direct repeats suggesting the deletion mechanism.

Conclusion

The results define species and biovar markers, confirm the dispensability of manB_O-Ag for O-polysaccharide synthesis and contribute to explain the lipopolysaccharide structure of rough and smooth Brucella species.