Abstract
Brucellosis is a worldwide zoonotic disease caused by Brucella spp. In China, brucellosis is recognized as a reemerging disease mainly caused by Brucella melitensis specie. To better understand the currently endemic B. melitensis strains in China, three Brucella genotyping methods were applied to 110 B. melitensis strains obtained in past several years. By MLVA genotyping, five MLVA-8 genotypes were identified, among which genotypes 42 (1-5-3-13-2-2-3-2) was recognized as the predominant genotype, while genotype 63 (1-5-3-13-2-3-3-2) and a novel genotype of 1-5-3-13-2-4-3-2 were second frequently observed. MLVA-16 discerned a total of 57 MLVA-16 genotypes among these Brucella strains, with 41 genotypes being firstly detected and the other 16 genotypes being previously reported. By BruMLSA21 typing, six sequence types (STs) were identified, among them ST8 is the most frequently seen in China while the other five STs were firstly detected and designated as ST137, ST138, ST139, ST140, and ST141 by international multilocus sequence typing database. Whole-genome sequence (WGS)-single-nucleotide polymorphism (SNP)-based typing and phylogenetic analysis resolved Chinese B. melitensis strains into five clusters, reflecting the existence of multiple lineages among these Chinese B. melitensis strains. In phylogeny, Chinese lineages are more closely related to strains collected from East Mediterranean and Middle East countries, such as Turkey, Kuwait, and Iraq. In the next few years, MLVA typing will certainly remain an important epidemiological tool for Brucella infection analysis, as it displays a high discriminatory ability and achieves result largely in agreement with WGS-SNP-based typing. However, WGS-SNP-based typing is found to be the most powerful and reliable method in discerning Brucella strains and will be popular used in the future.
Highlights
Brucellosis is one of the world’s most important zoonotic diseases causing great damage to husbandry industry and public health [1]
MLVA-8 Analysis Among 110 B. melitensis strains, MLVA-8 typing comprising eight panel 1 loci generated five genotypes, with variable-number tandem-repeat (VNTR) patterns described as 1-5-3-13-2-2-3-2 (82 strains, 75%), 1-5-3-13-2-3-3-2 (13 strains, 12%), 1-5-3-13-2-4-3-2 (11 strains, 10%), 1-5-3-13-32-3-2 (3 strains, 3%), and 1-5-3-14-2-2-3-2 (1 strain) (Table 1)
In this study, more strains were identified as the same MLVA-8 genotype, and they were exclusively collected from Xinjiang, suggesting the existence of a new lineage in this local area
Summary
Brucellosis is one of the world’s most important zoonotic diseases causing great damage to husbandry industry and public health [1]. In 1960s, a comprehensive control measures including animal vaccination, test-slaughter, and movement restriction were introduced to control this disease, thereafter a low-incidence period was observed from 1980s to 1990s. Over a long period of time, test-slaughter as major measure has been implemented to control brucellosis in domestic animals, this strategy is proven to be less effective. Other provinces with no vaccination implemented saw an increased number of brucellosis outbreaks in domestic animals, among them Xinjiang was mostly affected (from 413 in 2012 to 927 in 2015). From 2016, all the provinces in northern China will carry out vaccination program against brucellosis in bovine and small ruminants, more stringent rules will come into effect to restrict animal movement from brucellosis high-incidence region to low-incidence region. In support of the plan, bacteriological surveillance in domestic animal reservoir is emphasized
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