Background
Brucellosis, a zoonotic disease in Türkiye, which has significant direct and indirect impacts on the healthcare system and livestock. This study, which aimed to investigate the differences among
Brucella
spp. isolates originating from different regions of Türkiye, for implications for public health and veterinary medicine.
Method
Twenty-one isolates from ruminants and two isolates from humans obtained from various regions of Türkiye were utilized in the study. The isolates were identified and biotyped using traditional microbiological procedures, and whole-genome sequencing (WGS) was performed. This was followed by single nucleotide polymorphism (SNP)--based phylogenetic analysis and WGS-based analysis of virulence and resistance genes. Additionally, phenotypic antimicrobial resistance and phage susceptibilities were determined. The obtained data were then compared for concordance, ensuring the validity and reliability of the results.
Results
Our study, employing culture methods, polymerase chain reaction (PCR), and WGS analyses, identified 11
Brucella melitensis
(bv 3 (
n
= 9), one each bv 1 and bv 2) and 12
B. abortus
(bv 3 (
n
= 11), bv 9 (
n
= 1)) isolates All
B. abortus
isolates were of bovine origin, while the
B. melitensis
isolates were from sheep (
n
= 7), goat (
n
= 1), ram (
n
= 1), and humans (
n
= 2). In the whole-genome SNP-based phylogenetic tree, all
B. melitensis
strains were found to be of the IIb subtype of genotype II associated with the Eastern Mediterranean lineage. Ten different genotypes were identified in the SNP analysis of the isolates, with a maximum SNP difference of 278 and a minimum SNP difference of 4 among these genotypes. According to the WGS-SNP-based phylogenetic tree of
B. abortus
isolates, they were grouped in clade C1. In the SNP analysis, where ten different genotypes were identified, the SNP difference among these genotypes was a maximum of 316 and a minimum of 6.
In the in silico MLST analysis performed with WGS data,
B. melitensis
isolates were identified as ST8 and ST102 genotypes, while
B. abortus
isolates were identified as ST2 and ST3 genotypes. The dominant genotypes were ST8 for
B. melitensis
and ST2 for
B. abortus
, respectively. Virulence gene analysis conducted based on WGS data of the 23
B. abortus
and
B. melitensis
isolates revealed 43 virulence gene-associated regions in all strains, irrespective of species, host, or isolation year...