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. 2020 Jun 29;9(1):79.
doi: 10.1186/s40249-020-00697-0.

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

Hai-Tao Yuan  1 , Cheng-Ling Wang  2 , Li-Na Liu  3 , Dan Wang  1 , Dan Li  2 , Zhen-Jun Li  4 , Zhi-Guo Liu  5
Affiliations

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

Hai-Tao Yuan et al. Infect Dis Poverty. .

Abstract

Background: Hinggan League is located in the Northeast of the Inner Mongolia Autonomous Region, the historically endemic area of animal and human brucellosis. In this study, the epidemiological characteristics of human brucellosis were analyzed, and the genotypic profile and antimicrobial susceptibilities of Brucella melitensis strains isolated from humans in Hinggan League were investigated.

Methods: The epidemic characteristics were described using case number, constituent ratio, and rate. The 418 human blood samples were collected and tested by bacteriology, and suspect colonies were isolated and identified by conventional biotyping assays, the VITEK 2.0 microbial identification system, and AMOS (Brucella abortus, B. melitensis, B. ovis, and B. suis)-PCR. Subsequently, all strains were genotyped using multiple-locus variable-number tandem repeat analysis (MLVA) assays, and the antimicrobial susceptibility pattern of Brucella strains against the 10 most commonly used antibiotics was determined by microdilution method.

Results: A total of 22 848 cases of human brucellosis were reported from 2004 to 2019, with an annual average incidence of 87.2/100 000. The incidence rates in developed areas of animal husbandry (Horqin Youyi Qianqi [161.2/100 000] and Horqin Youyi Zhongqi [112.1/100 000]) were significantly higher than those in forest areas (Arxan [19.2/100 000]) (χ2 = 32.561, P < 0.001). In addition, peak morbidity occurred during May-August, accounting for 72.6% (16582/22 848) of cases. The highest number of cases occurred in the 40+ age group, accounting for 44.4% (10 137/22484) of cases, and morbidity in males was significantly higher than that in females in all age groups (χ2 = 299.97, P < 0.001), the most common occupation was farmers. A total of 54 B. melitensis strains were divided into 37 genotypes (GT1-37) with 80-100% genetic similarity. All 25 strains were sensitive to seven tested antibiotics, phenotypic resistance to cotrimoxazole and azithromycin was observed in 5 (20%) and 25 (100%) of the isolates, respectively.

Conclusions: Human brucellosis exhibited a significant increasing trend and B. melitensis is the main pathogen responsible for human brucellosis in this region. Improved surveillance of infected animals (sheep) and limiting their transfer and trade are optional strategies for decreasing the incidence of this disease.

Keywords: Antimicrobial susceptibility; Brucella melitensis; Brucellosis; Epidemiology characteristic; Genotyping; Hinggan league; Inner Mongolia Autonomous Region.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Demographic data of human brucellosis in Hinggan League during 2004–2019. a Annual reported cases and incidence rate (/100 000 people) of human brucellosis in Hinggan League during 2004–2019. b Average incidence rate of human brucellosis in various regions of Hinggan League during 2004–2019. c Distribution of human brucellosis cases at different ages and genders in Hinggan League during 2004–2019
Fig. 2
Fig. 2
Dendrogram based on the MLVA-16 genotyping assay (UPGMA method), showing relationships between the 54 B. melitensis isolates. The columns show the identification numbers, MLVA-16 genotypes (GT), panel 1 genotypes and MLVA-11 (panels 1 and 2A) genotypes, species-biovar, their geographic location, and the year of isolation of the strains
See this image and copyright information in PMC

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