Characteristics of Mycobacterium tuberculosis isolates from contact investigations in Korea, 2015-2017

Ha Jee Min, Lee Jeong Seob, Kim Young Mi, Song Seung Eun, Kwon Seung Jik, Yoo Jae Il, Kim Dong Hyeok
Division of Bacterial Diseases, Center for Laboratory Control of Infectious Disease, KCDC

Mycobacterium tuberculosis complex genotyping has proven to be an important tool for tuberculosis (TB) control and surveillance, and has provided new insight into the dynamics of disease transmission. In this study, we genotyped a total of 1,931 M. tuberculosis isolates from 1,669 congregate facilities, such as schools, companies, and hospitals etc., with conventional contact investigations from 2015 to 2017 in Korea using spoligotyping and 24-loci MIRU-VNTR. Based on the molecular typing results, 1,177 genotypes were identified from the 1,931 isolates, 940 (48.7%) of which had a unique genotype, while the others (51.3%) shared a profile with one or more other strains, and were categorized into 237 clusters. The results of spoligotyping indicated that 95.1% of the isolates belonged to known genotype clades. The largest spoligotype was the Beijing clade (80.53%), followed by the T1 clade (9.06%), H3 clade (0.93%), and T2 clade (0.88%). The most common genotype was TBG0381 (n = 65, 3.4%), followed by TBG0014 (n = 41, 2.1%), TBG0175 (n = 22, 1.1%), and TBG0100 (n = 21, 1.1%); all of the genotypes were included in the SIT 1-Beijing family. Moreover, the Beijing genotype strains showed a higher genomic clustering rate (OR = 7.7, 95% CI: 5.7-10.5) and TB transmission rate (OR = 4.0, 95% CI: 1.7-9.8) compared with non-Beijing genotype strains. In conclusion, our data suggest that the Beijing genotype is the most predominant genotype in Korea, and that a Beijing strain is associated with recent transmission events rather than a non-Beijing strain.

Keywords: Mycobacterium tubercuosis, Molecular typing, Genotypes