Abstract
BackgroundHinggan 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.MethodsThe 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.ResultsA 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.ConclusionsHuman 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.
Highlights
Hinggan League is located in the Northeast of the Inner Mongolia Autonomous Region, the historically endemic area of animal and human brucellosis
The epidemiology of human brucellosis and in vitro antimicrobial susceptibility characteristics of B. melitensis isolated from this region were determined
The results showed that the incidence rate of human brucellosis in the Hinggan League from 2004 to 2019 exhibited a significant increasing trend and imbalance in distribution among regions
Summary
Hinggan League is located in the Northeast of the Inner Mongolia Autonomous Region, the historically endemic area of animal and human brucellosis. 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. In humans, the disease can manifest as undulating fever with arthralgia, sometimes associated with chronic and severe complications, such as orchitis, spondylitis, and arthritis [3, 4]. People, especially those who engage in husbandry activities, slaughtering and livestock trading, are at higher risk of developing brucellosis. A comprehensive test of the antimicrobial susceptibility of human B. melitensis isolates from Inner Mongolia and China has not been performed
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