Genome Sequencing and Comparative Genomics of Indian Isolates of Brucella melitensis
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Date
2021
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Abstract
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.
Description
TNV_FM_Vol.12_2021_1
Keywords
Veterinary Science