Assessment of brucellosis-causing pathogens with an emphasis on the prevalence of Brucella melitensis in the Republic of Korea: insights from a decade of pathogen surveillance (2014-2023), a retrospective study.

Objectives: The main Brucella species causing human infections in the Republic of Korea is Brucella abortus, which uses cattle as its host. However, since 2014, Brucella melitensis, which uses sheep and goats as hosts, has also been identified. This study investigated whether a shift has occurred in the predominant species of Brucella pathogens.

Methods: Brucellosis is a class 3 infectious disease requiring mandatory reporting and registration in the Korea Disease Control and Prevention Agency's infectious disease surveillance system (http://is.kdca.go.kr). Cases from 2014 to 2023 were studied, and whole-genome sequencing analysis was conducted using BruMLSA21.

Results: Out of 51 patients, males (45 patients, 88.2%) were predominantly affected. Twentyfive patients (49%) came from the livestock industry, and within the livestock sector group, the route of infection occurred exclusively through contact (25/25, 100%), whereas in other occupations, it was split between contact (9/26 patients, 34.6%) and ingestion (8/26 patients, 30.8%). Among the 31 patients who underwent Brucella culture tests, B. melitensis was found to be more prevalent than B. abortus (14 patients, 45.2% vs. 11 patients, 35.5%). In all cases where B. melitensis was isolated, the infections were of foreign origin, consistent with the results of BruMLSA21.

Conclusion: Regular monitoring of the causative agent of brucellosis is necessary due to its varying host preferences and antibiotic resistance. Furthermore, given the increasing prevalence of B. melitensis worldwide, changes in dietary habits (e.g., increased lamb consumption), and the increase in foreign workers and Chinese immigrants, a multi-ministerial One Health response will be required.