Investigation of the molecular characteristics of Brucella isolates from Guangxi Province, China

Abstract

BackgroundHuman brucellosis has become a severe public health problem in China’s Guangxi Province, and there has been higher prevalence of brucellosis in this region after 2010. Both multiple locus variable-number tandem repeat analysis (MLVA) and multilocus sequence typing (MLST) assay schedules were used to genotype isolates and determine relationships among isolates.ResultsA total of 40 isolates of Brucella were obtained from humans, pigs, and dogs from 1961 to 2016. There were at least three species of Brucella detected in Guangxi Province, Brucella melitensis, Brucella suis, and Brucella canis, with 16, 17, and 7 isolates, respectively. Of which B. suis biovar 3 was the predominant species resulting in pig brucellosis in the area examined before 2000s. Moreover, B. melitensis biovar 3 was found to be mainly responsible for human brucellosis during 2012–2016. All B. melitensis isolates in this study belonged to East Mediterranean lineage. MLVA-11 genotype 116 was the dominant genotype and represented 81.2% of the isolates. MLVA cluster analysis showed there to be 44% (7/16) brucellosis cases caused by B. melitensis with a profile of outbreak epidemic from 2012 to 2016. However, nearly 83.3% (20/24) of brucellosis cases resulting from both B. suis and B. canis showed no epidemiological links or sporadic characteristics. MLVA-16 analysis confirmed extensive genotype-sharing events between B. melitensis isolates from Guangxi and other northern provinces within China. These data revealed that there are potential epidemiology links among these strains. B. suis strains of this study showed a unique genetic lineage at the global level and may have existed historically in this area. However, present B. canis isolates were closely related to previously reported isolates in Korea, where they may have originated. MLST typing showed that the population structure of Brucella strains had changed considerably in this province; ST17 and ST21, two previously predominant populations appeared to have been replaced by recently emerging ST8 group.ConclusionsOur investigation data have inspired the hypothesis that Guangxi Province had been subject to an imported human brucellosis epidemic. Our data suggest that strains found in Northern regions of China are the principal source of infections in recent cases of human brucellosis in Guangxi Province. Comparative genomic analysis from more strains is necessary to confirm this hypothesis. This work will facilitate better understanding of the epidemiology and improve the effectiveness of control and prevention of brucellosis in this region.

Brucella melitensis , a latent “travel bacterium,” continual spread and expansion from Northern to Southern China and its relationship to worldwide lineages

“…WGS-SNP analysis showed close relationships among strains from southern provinces, central, and many northern regions, indicating that B. melitensis strains from the southern region originated from northern regions. This conclusion is consistent with previous reports that the sources of infection of human brucellosis in southern regions (Guangxi, Hunan and Hainan Provinces) originated in northern provinces, including Inner Mongolia [25,26,41]. However, B. melitensis strains from China have a genetic relationship to strains from Asian regions including Russia, India, and Georgia, which are traditional epidemic regions of brucellosis.…”

“…B. melitensis strains were found in 14 provinces in China before 2000. Now, B. melitensis strains occur in 29 provinces (autonomous regions and cities) and B. melitensis is the dominant circulating species in southern regions of China [25,26]. This supports our hypothesis that B. melitensis has spread and expanded from northern to southern China.…”

Epidemiologically characteristics of human brucellosis and antimicrobial susceptibility pattern of Brucella melitensis in Hinggan League of the Inner Mongolia Autonomous Region, China

“…These results coincided with the serious human brucellosis epidemic [30], for which B. melitensis bv. 3 caused the majority of human brucellosis cases in northern and southern China [31][32][33]. However, 89% (48/54) of strains in this study carried MLVA-11 genotype 116; strains with this genotype have a vital epidemiological significance to the humans infected brucellosis [34].…”

ONE Health Approach to Address Zoonotic Brucellosis: A Spatiotemporal Associations Study Between Animals and Humans

“…A notable feature in our analysis is the presence of B. canis in all other hosts except for pig and yak. Human brucellosis caused by B. suis and B. canis in Guangxi, China ( 35 ) have also been reported earlier. An earlier study reports that B. canis is a rare source of human brucellosis in China ( 36 ), where B. melitensis has been the major pathogen associated with human brucellosis outbreaks.…”

“…According to statistics, there have been over 740 million domestic dogs in China in 2019 ( 38 ), relationships between pet dogs and human are getting more and more close, which emphasizes that canine brucellosis is a pressing concern. An earlier study had shown that Chinese isolates of B. suis strains had unique genetic lineages at the global level whereas the isolates of B. canis were closely homologous to strains from Korea ( 35 ). Despite this disease being the most widespread zoonosis globally, it is also true that it remains severely neglected as a potential cause for chronic, debilitating maladies for multiple reasons such as its non-descript clinical presentation in human populations and its varying degree of clinical presentations ( 11 ).…”