Brucellosis is caused by the genus Brucella and is known as a major bacterial zoonotic disease. Although there has been great progress in controlling the disease in many countries, there still remain regions where the infection persists in domestic animals and, consequently, transmission to the human frequently occurs. In Korea, the number of human brucellosis cases increased sharply to 215 in 2006 when the number of outbreaks also reached a peak among animals. The number of human cases and bovine outbreaks has declined starting in 2007 by continuous effort of eradication in bovine brucellosis. Since the first case of human brucellosis in 2002, all brucellosis cases were caused by B. abortus except the overseas inflow cases of B. melitensis. In this study we introduce three isolated human B. abortus cases in 2016~2017 which were requested to Korea CDC.
Suspected 55 blood samples of brucellosis were sent to Korea CDC in 2016~2017 and inoculated into media of BACTEC system to cultivate. After several passages using Brucella agar plate, the pure isolates were examined by classical biotyping methods, and PCR test using Brucella-specific primers, Brucella species specific multiplex PCR, and real time PCR. The sequence from PCR was also analysed.
As a result, 3 of 55 samples were identified as B. abortus. They were grown in Brucella agar plate and showed positive result for H2S production, oxidase and urease. DNA from isolates were extracted and amplified in Brucella genes and were positive in B. abortus specific multiplex PCR. In real time PCR these showed positive results in B. abortus specific target genes.
These three cases identified as B. abortus had clinical history of eating uncooked meat or contacting with cattles. In Korea, B. abortus biotype 1 were major pathogenic species in human and animals. In these cases there is need to investigate more about biotyping and molecular typing between human isolates and cattle isolates to understand the exact relationship. Although the case of brucellosis in human and animals become low, people need to know B. abortus is still exist and pose a threat to human in Korea.
Acknowledgements: This work was supported by Korea Centers for Disease Control and Prevention
(2016-NG52002-00, 4837-301-210-13)