ABSTRACT
Objective:To analyze the genetic characteristics of Brucella strains isolated from a human brucellosis epidemic in Baoding City of Hebei Province, and to provide scientific basis for control and prevention of brucellosis. Methods:Brucella antibody was detected in a high-risk population ( n=22) of brucellosis in Baoding City in 2018 by using rose bengal plate test and tube agglutination test. Blood samples of patients with brucellosis were collected for Brucella isolation ( n=3). Conventional methods were used to identify the bacteria strains. Multiple locus variable-number tandem repeat analysis (MLVA) and multilocus sequence typing (MLST) were used to analyze the genetic characteristics of the strains. Results:The sero-prevalence of Brucella antibodies in high-risk populations was 4.55% (1/22). Three suspected Brucella strains were isolated from blood samples of three patients (No. BDY-1, BDY-2 and BDY-3) and were identified as Brucella melitensis biovar 3. The results of MLVA showed that strain BDY-1 and strain BDY-2 were the same genotype. Strain BDY-3 added two tandem repeats at the locus of Bruce04 and Bruce16, respectively, and lost three tandem repeats at the locus of Bruce30. The genotype of panel 1 (MLVA-8) and panel 1 + panel 2A (MLVA-11) were 42 and 116, respectively, which belonged to the "East Mediterranean group". They were closely clustered with Brucella melitensis biovar 3. MLST analysis showed that all isolated strains could be classified into a ST8 type. Conclusions:The isolated strains from the epidemic are Brucella melitensis biovar 3. In the future, the prevention and control of brucellosis in Baoding City should strengthen the health education and behavior intervention of the high-risk population.