Whole-genome sequencing for genetic diversity analysis of Iranian Brucella spp. isolated from humans and livestock

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.

Phylogenetic Analysis and Comparative Genomics of Brucella abortus and Brucella melitensis Strains in Egypt

Brucellosis is a notifiable disease induced by a facultative intracellular Brucella pathogen. In this study, eight Brucella abortus and eighteen Brucella melitensis strains from Egypt were annotated and compared with RB51 and REV1 vaccines respectively. RAST toolkit in the BV-BRC server was used for annotation, revealing genome length of 3,250,377 bp and 3,285,803 bp, 3289 and 3323 CDS, 48 and 49 tRNA genes, the same number of rRNA (3) genes, 583 and 586 hypothetical proteins, 2697 and 2726 functional proteins for B. abortus and B. melitensis respectively. B. abortus strains exhibit a similar number of candidate genes, while B. melitensis strains showed some differences, especially in the SRR19520422 Faiyum strain. Also, B. melitensis clarified differences in antimicrobial resistance genes (KatG, FabL, MtrA, MtrB, OxyR, and VanO-type) in SRR19520319 Faiyum and (Erm C and Tet K) in SRR19520422 Faiyum strain. Additionally, the whole genome phylogeny analysis proved that all B. abortus strains were related to vaccinated animals and all B. melitensis strains of Menoufia clustered together and closely related to Gharbia, Dameitta, and Kafr Elshiek. The Bowtie2 tool identified 338 (eight B. abortus) and 4271 (eighteen B. melitensis) single nucleotide polymorphisms (SNPs) along the genomes. These variants had been annotated according to type and impact. Moreover, thirty candidate genes were predicted and submitted at GenBank (24 in B. abortus) and (6 in B. melitensis). This study contributes significant insights into genetic variation, virulence factors, and vaccine-related associations of Brucella pathogens, enhancing our knowledge of brucellosis epidemiology and evolution in Egypt.

Characterization of Brucella spp. circulating in industrial dairy cattle farms in Iran: a field study 2016 - 2023

Bovine brucellosis, an infectious disease transmitted by Brucella melitensis and Brucella abortus, presents a significant zoonotic risk for agricultural economics and animal health. The primary objective of this study was to present a comprehensive understanding of the prevalence and features of Brucella strains within the industrial dairy farming sector in Iran. Rose Bengal plate test, standard agglutination test, and indirect enzyme linked immunosorbent assay tests were used to confirm all seropositive animals. A total number of 1,311 bovine samples from seropositive animals including were collected from 224 farms in 21 provinces of different regions of Iran and examined. The discovered Brucella isolates were phenotyped and molecularly characterized. The isolates were all B. abortus or B. melitensis. Bacteria analysis revealed that 70.53% of seropositive farms were tested positive for Brucella strains, predominantly B. melitensis biovar 1 (43.42%) and B. abortus biovar 3 (27.11%). Geographical distribution revealed that B. melitensis biovar 1 was the most common in dairy cow farms (16 provinces), followed by B. abortus biovar 3 (six provinces). Also, the prevalence of B. melitensis biovar 2, B. melitensis biovar 3, B. abortus biovar 1, B. abortus biovar 2 and RB51 vaccine were restricted to certain provinces. AMOS (abortus melitensis ovis suis)-polymerase chain reaction and Bruce-ladder PCR confirmed species identification. These results highlighted the complexity of bovine brucellosis in Iran and illustrated that B. melitensis was spread from small ruminants to cattle. This study provided important epidemiological insights for targeting future brucellosis control programs in the Iranian dairy farms.

Molecular epidemiological characteristics of osteoarthritis-associated Brucella melitensis in China: evidence from whole-genome sequencing-based analysis

BACKGROUND

Brucellosis, developing complications including arthritis, spondylitis, sacroiliitis, and osteomyelitis, is one of the most common zoonotic diseases in the current world which causes economic losses to the livestock industry and is a great public health concern. Brucella melitensis are the main pathogen of brucellosis epidemics in China, most of which are located in northern China. However, there is limited knowledge about the epidemiology of osteoarthritis-associated brucellosis. This study was aimed to reveal the prevalence of osteoarthritis-associated brucellosis in Inner Mongolia and also to investigate the molecular characteristics of B. melitensis isolates.

METHODS AND RESULTS

In 2018, the osteoarthritis symptoms of brucellosis in the Brucellosis department of a hospital in Inner Mongolia were investigated. Twenty osteoarthritis-associated B. melitensis strains, isolated from the inpatients in Inner Mongolia during 2013-2017, were subjected to whole genome sequencing. The multilocus sequence type (MLST) and core genome SNP (cgSNP) analysis were conducted to detect molecular epidemiological characteristics. The incidence of brucellosis osteoarthritis symptoms in males (85/120, 70.8%) was significantly higher than that in females (35/120, 29.2%), and the age of patients was concentrated between 41 and 60 years old. In silico analyses indicated ST8 was the prevalent sequence type and the transmission of osteoarthritis-associated B. melitensis among different geographical areas. All strains carry virulence genes, including cgs, lpsA, manCoAg, pgm, pmm, virB4, wbdA and wboA.

CONCLUSION

Our study showed the close epidemiologically connection of osteoarthritis-associated B. melitensis strains in northern China. And ST8 was the prevalent sequence type which need our attention.

Genetic diversity of Brucella melitensis isolates from sheep and goat milk in Iran

The genetic diversity of Brucella strains has not been fully understood. To investigate this, the genetic characteristics of 64 isolates of Brucella melitensis from sheep and goats' milk were studied using random fragment length polymorphism (RFLP) and multiple locus variable-number tandem repeat analysis (MLVA-16) methods developed in Orsay, France (MLVA-16Orsay). The RFLP analysis revealed that all 64 isolates were of biovar one. The MLVA-typing showed that one sample was simultaneously infected with two strains of B. melitensis and the genotype of 65 isolate was analyzed. Four genotypes (47, 42, 43, and 63) were identified using MLVA-8 (panel 1), whereas six genotypes (138, 125, 116, 108, and two unknown genotypes) were identified using MLVA11 (panels 1 and 2A). From the review of MLVA-16 (panels 1, 2A, and 2B), panel 2B showed a very high discriminatory power. Two loci of Bruc04 and Bruc30 from this panel had diversity index values higher than 0.71 and the average diversity index was 0.619. So MLVA-16Orsay 34 showed the genotype indicating a low genetic homogeneity among the isolates. The findings of MLVA genotyping of the isolates suggest that strains of B. melitensis isolated from the milk of small ruminants in Iran are most closely related to the isolates from neighboring countries of the Eastern Mediterranean group. To the best of our knowledge, this is the first study to indicate the potential use of MLVA genotyping for simultaneous detection of specimen contamination using two different B. melitensis biovars.

Genotypic peculiarities of a human brucellosis case caused by Brucella suis biovar 5

Human brucellosis cases are rare in non-endemic countries, such as Germany, where infections are predominantly caused by Brucella melitensis. The German National Reference Laboratory for Bovine, Porcine, Ovine and Caprine Brucellosis received a suspected Brucella sp. isolate from a patient for identification. Bacteriological tests and PCR-based diagnostics showed the isolate to be B. suis, but did not yield cohesive results regarding the biovar. Whole genome sequencing and subsequent genotyping was employed for a detailed characterization of the isolate and elucidating the reason for failure of the diagnostic PCR to correctly identify the biovar. The isolate was found to be B. suis bv. 5, a rare biovar with limited geographical distribution primarily found in the Northern Caucasus. Due to a deletion in one of the target regions of the diagnostic PCR, the isolate could not be correctly typed. Based on in silico genotyping it could be excluded that the isolate was identical to one of the B. suis bv. 5 reference strains. Here, we report a rare case of a B. suis bv. 5 field isolate. Furthermore, by reporting this finding, we want to make practitioners aware of possible misinterpretation of PCR results, as it cannot be excluded that the detected deletion is common among the B. suis bv. 5 community, as there is currently a lack of field isolates.

Shedding rate of Brucella spp. in the milk of seropositive and seronegative dairy cattle

Brucellosis in cattle herds has caused severe economic losses in many regions worldwide. A cross-sectional study was performed to investigate the presence of Brucella spp. in industrial dairy cattle farms in Iran. For this purpose, 935 blood and 935 milk samples were randomly collected from industrial dairy cattle farms in Iran's Alborz and Tehran provinces. Blood and milk samples were collected on the same day from each cow. Serological, bacteriological, and molecular characterization of Brucella isolates were performed using standard methods. Our results revealed the seroprevalence of brucellosis in dairy cattle farms in the Alborz and Tehran provinces, reaching 19.8%, 6.7%, 5.1%, 14.1%, and 13.1% using the Rose Bengal plate test (RBPT), serum agglutination test (SAT), 2-mercaptoethanol test (2-ME), indirect enzyme-linked immunosorbent assay (i-ELISA) and milk ring test (MRT), respectively. Furthermore, the results of bacterial culture and PCR analyses showed the presence of Brucella abortus among dairy cattle in the Alborz province and Brucella melitensis and B. abortus among dairy cattle in the Tehran province. Moreover, statistical analysis with Cohen's Kappa has highlighted the near-perfect agreement between RBPT and i-ELISA (k = 0.86). In contrast, substantial agreement was shown between RBPT and SAT performance (k = 0.70) and moderate agreement between RBPT and 2-ME (k = 0.67). The findings of this investigation showed shedding of Brucella in the milk of seropositive cows, which is a serious problem involving the maintenance and further spread of Brucella infection on the farm. Therefore, for brucellosis detection or eradication in dairy cattle farms, bacteriological and serological tests of milk samples should be performed along with blood analysis to inhibit the uncontrolled spread of the disease in animals and humans.