Conserved intracellular virulence architecture and focal genomic diversification in sub-Saharan African Brucella melitensis.

Authors

Samweli Y Bahati, Eliezer Brown Mwakalapa, Henry G Mung'ong'o, Abdalah Makaranga, Benson Kidenya, Reuben S Maghembe

Published in

Microbiology spectrum. Volume 14. Issue 10. Pages e0170326. Oct 06, 2026. Epub Aug 19, 2026.

Abstract

Brucella melitensis has a highly conserved genome, but the distribution of core-genome, gene-content, virulence-associated, mobile-element-associated, and antimicrobial-resistance-relevant variation among available sub-Saharan African genomes has not been examined in an integrated regional analysis. We analyzed 51 curated B. melitensis genomes from human and animal hosts using core-genome phylogenomics, pangenome reconstruction, virulence profiling, mobile genetic element (MGE) analysis, and mutation-based screening of antimicrobial resistance (AMR)-associated loci. A phylogeny reconstructed from 6,060 shared SNP sites resolved a dominant ST12-associated lineage, together with ST7, ST8, ST42, and novel sequence type branches. Individual genomes differed from the reference by 1,677-2,579 SNPs. The pangenome comprised 3,457 gene families, including 3,049 persistent families, indicating strong genome conservation, and limited accessory expansion. Virulence profiling identified 66 VFDB-associated genes; 48 genomes carried all 66, and the remaining three retained more than 98% of the virulence repertoire. Conserved determinants included the VirB type IV secretion system, lipopolysaccharide biosynthesis, intracellular survival pathways, and stress-response functions. MGE-associated variation was restricted to a small number of regions dominated by transposases and insertion-sequence-associated proteins. A GspF-domain-containing secretion-associated locus was detected only in BM2, although no complete type II secretion system gene cluster was identified. Recurrent substitutions occurred in AMR-relevant chromosomal loci, including rpoB, gyrA, gyrB, parC, parE, folA, folP, bepCDEFG, and mprF, but none corresponded to validated resistance-conferring alleles. The available regional genomes therefore comprise multiple phylogenetic lineages within a strongly conserved gene and intracellular virulence framework, with diversity concentrated in core-genome SNPs and localized genomic regions.
Brucella melitensis is a major zoonotic pathogen at the livestock-human interface, but genome-resolved evidence from sub-Saharan Africa remains limited. This study curates available regional genomes and shows that the population is dominated by a conserved intracellular virulence backbone, strong core-genome conservation, and focal genomic diversification rather than by extensive accessory-genome expansion. By integrating phylogenomics, pangenome analysis, virulence profiling, mobile-element characterization, and mutation screening of antimicrobial-resistance-associated loci, the work provides a regional framework for One Health genomic surveillance and identifies candidate loci requiring phenotype-linked validation.

PMID:
42615649
Bibliographic data and abstract were imported from PubMed on 10 Nov 2026.

Read full publication at:
Please sign in to see all details.

Stats

1-terrible, 9-excellent. How would you rate this publication? Sign in in to submit your rating.

Post a comment

You need to be signed in to post comments. You can sign in here.

Comments

There are no comments yet.