Abstract
Brucellosis has been reported in several regions of Hainan Province, but the extent of the disease has not been fully elucidated. Conventional biotyping methods, multiple locus variable number tandem repeats analysis (MLVA), and single-nucleotide polymorphisms (SNPs) from draft genome sequencing were employed to characterize the strains. There were four biovars (Brucella melitensis bv. 1, 2, and 3 and Brucella suis bv. 3) detected, which showed that the biovar diversity of Brucella in Hainan is higher than in other areas of China. Both B. melitensis bv. 3 and B. suis bv. 3 were dominant species and showed epidemiology patterns that were compatible with both southern and northern China. Eight of MLVA-11 genotypes were known (31, 111, 116, 120, 136, 291, 297, and 345), and the remaining seven were novel (HN11-1 to HN11-7); these data showed that Brucella strains in this study had multiple geographic origins and exhibited characteristics of origin and evolution of co-existing imported and Hainan specific lineage. A total of 41 strains were found, belonging to 37 unique genotypes that each represented a single strain, which suggests that these strains were not directly related epidemiologically and indicates that the epidemic characteristics of human brucellosis in Hainan was dominated by sporadic strains. The high HGDI values were observed in MLVA-8, MLVA-11, and MLVA-16 among two species, suggesting considerable genetic diversity among these species. MST is characterized based on MLVA-16 that was found both throughout China and on a global level and showed that strains of this study had significant genetic differences with strains from many parts of the globe and seemingly represent a unique genetic lineage. Whole-genome SNP analysis showed that four B. melitensis were closely related to strains from China’s northern provinces, and the source of infection was partly of human brucellosis in this province that may have been from these regions. The B. suis were closely related to strains from the United States, and further investigation of the transportation of animals, such as pigs, is needed to elucidate the origins of these strains.
Highlights
Brucellosis is a zoonosis affecting a wide range of domestic and wild animals and humans (Marvi et al, 2018)
All of the 41 Brucella strains were identified as B. melitensis bv. 1 (n = 5), B. melitensis bv. 2 (n = 1), B. melitensis bv. 3 (n = 23), and B. suis bv. 3 (n = 12) using classical biotyping methods (Table 1)
The 41 Brucella strains were observed in nine counties in Hainan Province, including Ledong (n = 1), Lingshui (n = 1), Wanning (n = 2), Chengmai (n = 2), Dingan (n = 3), Sanya (n = 3), LinGao (n = 7), Haikou (n = 8), and Dongfang (n = 13), and the original locations associated with the other strains are unknown (Figure 1)
Summary
Brucellosis is a zoonosis affecting a wide range of domestic and wild animals and humans (Marvi et al, 2018). Human brucellosis cases had been reported in almost all China provinces since 2010 (Lai et al, 2017). In Hainan Province, which is located at the southernmost part of China, there were no historically reported brucellosis cases, and only one human brucellosis case was reported in Danzhou in 1985, brucellosis cases significantly increased in 2017 between humans (Wang et al, 2019), but the available information on the extent of the disease and relatedness among strains is unknown. The purpose of this study is to analyze these Brucella strains using bio-typing and to arrange the molecular scheme including MLVA and WGS to elucidate prevalence characteristics and relatedness among strains for epidemiological purposes, and to provide useful information for the control and prevention of brucellosis in Hainan Province
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