Dataset Information

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

ABSTRACT: 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.

SUBMITTER: Holzapfel M

PROVIDER: S-EPMC6204395 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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

Holzapfel Marion M Girault Guillaume G Keriel Anne A Ponsart Claire C O'Callaghan David D Mick Virginie V

Frontiers in microbiology 20181022

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 ...[more]

PMID: 30405566

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Project description:Brucellosis, caused by Brucella spp., is one of the most widespread bacterial zoonoses worldwide. Vaccination is still considered the best way to control brucellosis. An investigation into the differential proteome expression patterns of wild and vaccine strains may help researchers and clinicians differentiate between the strains to diagnose and better understand the mechanism(s) underlying differences in virulence. In the present study, a mass spectrometry-based, label-free relative quantitative proteomics approach was used to investigate the proteins expressed by the wild strain, B. melitensis biovar 3 and compare it with those expressed by B. melitensis M5-90. The higher level of virulence for B. melitensis biovar 3 compared to B. melitensis M5-90 was validated in vitro and in vivo. A total of 2133 proteins, encompassing 68% of the theoretical proteome, were identified and quantified by proteomic analysis, resulting in broad coverage of the B. melitensis proteome. A total of 147 proteins were identified as differentially expressed (DE) between these two strains. In addition, 9 proteins and 30 proteins were identified as unique to B. melitensis M5-90 and B. melitensis biovar 3, respectively. Pathway analysis revealed that the majority of the DE proteins were involved in iron uptake, quorum sensing, pyrimidine metabolism, glycine betaine biosynthetic and metabolic processes, thiamine-containing compound metabolism and ABC transporters. The expression of BtpA and VjbR proteins (two well-known virulence factors) in B. melitensis biovar 3 was 8-fold and 2-fold higher than in B. melitensis M5-90. In summary, our results identified many unique proteins that could be selected as candidate markers for differentiating vaccinated animals from animals with wild-type infections. BtpA and VjbR proteins might be responsible for the residual virulence of B. melitensis M5-90, while ABC transporters and thiamine metabolism associated proteins may be newly identified Brucella virulence factors. All of the identified DE proteins provide valuable information for the development of vaccines and the discovery of novel therapeutic targets.

Project description:Brucella melitensis causes small ruminant brucellosis and a zoonotic pathogen prevalent worldwide. Whole genome phylogeny of all available B. melitensis genomes (n = 355) revealed that all Indian isolates (n = 16) clustered in the East Mediterranean lineage except the ADMAS-GI strain. Pangenome analysis indicated the presence of limited accessory genomes with few clades showing specific gene presence/absence pattern. A total of 43 virulence genes were predicted in all the Indian strains of B. melitensis except 2007BM-1 (ricA and wbkA are absent). Multilocus sequence typing (MLST) analysis indicated all except one Indian strain (ADMAS-GI) falling into sequence type (ST 8). In comparison with MLST, core genome phylogeny indicated two major clusters (>70% bootstrap support values) among Indian strains. Clusters with <70% bootstrap support values represent strains with diverse evolutionary origins present among animal and human hosts. Genetic relatedness among animal (sheep and goats) and human strains with 100% bootstrap values shows its zoonotic transfer potentiality. SNP-based analysis indicated similar clustering to that of core genome phylogeny. Among the Indian strains, the highest number of unique SNPs (112 SNPs) were shared by a node that involved three strains from Tamil Nadu. The node SNPs involved several peptidase genes like U32, M16 inactive domain protein, clp protease family protein, and M23 family protein and mostly represented non-synonymous (NS) substitutions. Vaccination has been followed in several parts of the world to prevent small ruminant brucellosis but not in India. Comparison of Indian strains with vaccine strains showed that M5 is genetically closer to most of the Indian strains than Rev.1 strain. The presence of most of the virulence genes among all Indian strains and conserved core genome compositions suggest the use of any circulating strain/genotypes for the development of a vaccine candidate for small ruminant brucellosis in India.

Dataset Information

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

Publications

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

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