Identification and distribution of Mycobacterium leprae genotypes in a region of high leprosy prevalence in China: a 3-year molecular epidemiological study.

Multiple-locus variable-number tandem-repeat (VNTR) analysis (MLVA) has been proposed as a means of strain typing for tracking the transmission of leprosy. However, empirical data for a defined population are lacking. To this end, a study was initiated to assess the diversity and distribution of prevalent Mycobacterium leprae strains in Qiubei County, Yunnan Province, People's Republic of China, where the annual detection rate of leprosy is 10-fold higher than the national average rate. Sixty-eight newly diagnosed leprosy patients were included in the study. MLVA at eight M. leprae loci was applied using DNA extracts from skin biopsies. The number of alleles per locus ranged from 4 to 24, providing adequate strain discrimination. MLVA strain typing identified several clusters of patients whose M. leprae specimens shared similar VNTR profiles. Two of these clusters were comprised of patients who resided predominantly in the north and northwest parts of Qiubei County. Furthermore, it was found that multicase families are common in this county: 23 of the 68 patients were from 11 families. Intrafamilial VNTR profiles closely matched within six families, although they were different between the families. Moreover, VNTR patterns related to those found in some multicase families were also detected in patients in the same or adjacent townships, indicating the utility of VNTR strain typing to identify and detect short-range transmission events. Social contact through village markets is proposed as a means of transmission.