Objective:To study the clinical characteristics of patients with brucella bloodstream infection in different age groups, and provide a basis for clinicians to take targeted diagnosis and treatment measures. Methods:Demographic data and general condition (age, sex, occupation, location, onset season, source of infection, clinical stage), clinical characteristics (main clinical symptoms and complications), and laboratory test results (routine and pathogenic tests) of adult patients with brucella bloodstream infection admitted to the Affiliated Hospital of Chengde Medical College from January 2015 to January 2020 were collected. According to the age stratification standards recommended by the World Health Organization, the patients were divided into a young group (18 - 44 years old), a middle-aged group (45 - 59 years old), and an elderly group (≥60 years old), and various indicators among different age groups were compared and analyzed. Results:A total of 75 patients were included, including 15 cases (20.00%) in the young group, 37 cases (49.33%) in the middle-aged group, and 23 cases (30.67%) in the elderly group. Among them, 61 cases (81.33%) were males and 14 cases (18.67%) were females, with statistically significant differences in gender ratios among different age groups (χ 2 = 7.28, P = 0.021). The majority of patients were farmers (64 cases, 85.33%), and 92.00% (69/75) of the patients came from rural areas. The main sources of infection were infected cattle and sheep, and contaminated food (39 cases, 52.00%). The main season of onset was spring and summer (45 cases, 60.00%). The clinical staging was mainly in the acute phase (66 cases, 88.00%). In terms of clinical symptoms, the young group of patients had no symptoms of low back pain, while the incidence rates of low back pain in the middle-aged and elderly groups were 35.14% (13/37) and 30.43% (7/23), respectively. There was a statistically significant difference between the three groups (χ 2 = 6.98, P = 0.031). In terms of complications, there were no cases of concurrent spondylitis in the young group of patients. The incidence rates of spondylitis in the middle-aged and elderly groups were 32.43% (12/37) and 34.78% (8/23), respectively. There was a statistically significant difference among the three groups (χ 2 = 6.86, P = 0.032). In terms of routine laboratory examinations, there were statistically significant differences in the proportion of blood lymphocytes and albumin levels among patients of different age groups ( F = 3.41, 3.27, P = 0.038, 0.044). In terms of pathogenic examination, there was a statistically significant difference in the median alarm time for positive blood culture among patients of different age groups ( H = 9.54, P = 0.008), with the middle-aged group having the longest (66.24 h) and the elderly group having the shortest (58.80 h). Conclusions:The clinical characteristics of patients with brucella bloodstream infection vary among different age groups, middle-aged and elderly patients are prone to low back pain symptoms, accompanied by spondylitis. Clinicians should pay attention to the patient's own characteristics and provide targeted diagnosis and treatment.