Genotyping of Mycobacterium leprae for understanding the distribution and transmission of leprosy in endemic provinces of China.

OBJECTIVES: Understanding the nature of Mycobacterium leprae transmission is vital to implement better control strategies for leprosy elimination. The present study expands the knowledge on county-levels strain diversity, distribution and transmission patterns of leprosy in endemic provinces of China.

METHODS: We genetically characterized 290 clinical isolates ofM. leprae from four endemic provinces using variable number tandem repeats (VNTR) and single nucleotide polymorphisms (SNPs). Attained genetic profiles and cluster consequences were contrasted with geographical and migration features of leprosy at county levels.

RESULTS: Considering the allelic variability of 17 VNTR loci by differentiating index, the (GTA)9, (AT)17, (AT)15, (TA)18, (TTC)21 and (TA)10 are reported to be highly polymorphic than other loci. The VNTR profile generated the low density clustering pattern in the counties of Sichuan and Yunnan, whereas clusters have been observed from the isolates from Huayuan (N = 6), Yongding (N = 3), Zixing (N = 3), Chenxi (N = 2) and Zhongfang (N = 2) of Hunan; Zhijin (N = 3), Anlong (N = 2), Zhenning (N = 2), and Xixiu (N = 2) counties of Guizhou. In some clusters, social relations of the people have been observed between villages. From the 290 clinical isolates, the most predominantly reported SNP was 3 K (278, 95.8%) followed by SNP 1D (10, 3.4%) which are typically considered to be predominant in China. Additionally, we detected the novel SNP 3 J (2, 0.8%) that has not yet been reported in China.

CONCLUSION: The clustering pattern ofM. leprae indicate the transmission of leprosy still persists at county levels, suggesting that there is a need to implement better approaches to trace the close contacts of leprosy patients.