Genotyping of Brucella isolates from animals and humans by Multiple-Locus Variable-number Tandem Repeat Analysis (MLVA)

A Comprehensive Bibliometric Analysis of Brucellosis Research: Insights from CNKI and Web of Science Databases (2014-2023)

Purpose

This study aimed to analyze the current status, research hotspots, and frontiers of brucellosis from 2014 to 2023 using data from China National Knowledge Infrastructure (CNKI) and Web of Science (WoS) via CiteSpace, and to provide new insights for researchers in the field.

Material and Methods

Articles related to brucellosis published from 2014 to 2023 were retrieved from CNKI and WoS databases. CiteSpace V.6.3.R3 was employed to generate network maps and perform bibliometric analysis.

Results

A total of 467 references from CNKI and 3686 references from WoS were analyzed. In CNKI, the annual publication trend showed a decline, with Xu Liqing, Ma Li, and Yang Xuxin being the most prolific authors, and the Chinese Center for Disease Control and Prevention being the leading institution. The keyword cluster analysis identified 13 main clusters, while the keyword emergence map highlighted 15 keywords with the strongest emergence intensity. In contrast, WoS displayed an increasing trend in annual publications, with Heinrich Neubauer, Egyptian Knowledge Bank (EKB), and China as the top contributors in terms of authors, institutions, and countries, respectively. "Infection" was the most frequently occurring keyword. WoS analysis revealed 16 primary clusters and 25 keywords with high emergence intensity.

Conclusion

Between 2014 and 2023, CNKI saw a slight dip in brucellosis studies, while WoS research on it gained growing attention. CNKI literature primarily focuses on epidemiology, clinical manifestations, complications, and diagnostic methods, while WoS literature emphasizes pathogenesis and public health management. Effective prevention and control of brucellosis require interdisciplinary, cross-sectoral, and transnational cooperation.

Molecular epidemiology of brucellosis in Asia: insights from genotyping analyses

Brucellosis infects humans and animals worldwide but is particularly prevalent in Asia. In many Asian countries, molecular diagnostic tools for accurate molecular diagnostics and molecular epidemiology are lacking. Nonetheless, some countries have conducted in-depth molecular epidemiological studies. The objective of this study was to reveal the genetic relationships, geographic origins, and distributions of Brucella strains across Asia for two primary species, B. abortus and B. melitensis. For this, we systematically searched genotyping data from published studies on the molecular epidemiology of Brucella species for both humans and livestock in Asia. We used data from multilocus sequence typing (MLST), multiple-locus variable-number tandem repeat analysis (MLVA), and whole genome sequencing analysis of Brucella strains. We also analyzed the MLVA genotypes of 129 B. abortus isolates and 242 B. melitensis isolates with known origins in Asia from an online MLVA database using MLVA-11 data in minimum spanning trees and MLVA-16 data in neighbor-joining trees. We found that the B. melitensis East Mediterranean lineage is predominant across the continent, with only a small number of samples from the Africa and Americas lineages, and none from the West Mediterranean lineage. The "abortus C" genotype was the most common group of B. abortus in Asia, with limited genetic variation for this species. Several studies also reported that Near Eastern countries frequently encounter human brucellosis cases of B. abortus from genotypes 42 and 43. Our study highlights the inconsistent collection of genetic data for Brucella species across Asia and a need for more extensive sampling in most countries. Finally, a consistent nomenclature is necessary to define various groupings of strains within a lineage (i.e., clade) so uniform terminology should denote particular genetic groups that are understood by all researchers.

Whole-genome sequencing-based analysis of Brucella species isolated from ruminants in various regions of Türki̇ye

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. Although classical resistance-related genes were not detected by WGS-based antimicrobial resistance gene analysis, phenotypic resistance analysis revealed resistance to azithromycin, rifampin, and trimethoprim/sulfamethoxazole in B. abortus and B. melitensis isolates.

CONCLUSION

Both B. melitensis and B. abortus were circulating species in animals and human. The dominant genotypes were ST8 for B. melitensis and ST2 for B. abortus, respectively. All B. melitensis strains were found to be of the IIb subtype of genotype II associated with the Eastern Mediterranean lineage, while B. abortus isolates, they were grouped in clade C1. Further, a comprehensive study with a sufficient number of isolates covering all regions of Türkiye would provide more accurate information about the current epidemiological situation in the country.

Phylogenetic Analysis of Brucella melitensis Strains Isolated from Humans Using 16S rRNA Sequencing and Multiple Locus Variable Number of Tandem Repeats Analysis-16

Background: Brucellosis is the most important public health problem worldwide, and the annual incidence of the disease in humans is 2.1 million. The Brucella genome is highly conserved, with over 90% similarity among species. The aim of this study was to perform species-level identification of Brucella spp. strains isolated from humans diagnosed with brucellosis and to further investigate the phylogenetic relationships using multiple locus variable number of tandem repeats analysis (MLVA)-16 and 16S rRNA sequencing analysis. Materials and Methods: Brucella spp. was isolated from the blood cultures of 54 patients who tested positive for brucellosis through serological examinations. Real-time PCR was used to identify the isolates in species, and the genus level of Brucella was confirmed with 16S rRNA. All isolates were subjected to phylogenetic analysis using variable number of tandem repeat analysis with multiple loci. Results: Subsequent analysis via real-time PCR confirmed these isolates to be of the Brucella melitensis species. The 16S rRNA sequence analysis showed 100% homogeneity among the isolates. MLVA revealed the formation of five different genotypic groups. While two groups were formed based on the 16S rRNA sequence analysis, five groups were formed in the MLVA. Conclusions: The study concluded that 16S rRNA sequence analysis alone did not provide sufficient discrimination for phylogenetic analysis but served as a supportive method for identification. MLVA exhibited higher phylogenetic power. The widespread isolation of B. melitensis from human brucellosis cases highlights the importance of controlling brucellosis in small ruminants to prevent human infections.