Loop-mediated isothermal amplification (LAMP) assay targeting RLEP for detection of Mycobacterium leprae in leprosy patients.

OBJECTIVE: Leprosy is a chronic infectious disease caused by Mycobacterium leprae and it remains a significant health problem in several parts of the world. Early and accurate diagnosis of this disease is therefore essential. Previously published loop-mediated isothermal amplification (LAMP) protocols for detecting mycobacterial species used conventional primers targeting the 16S rRNA, gyrB and insertion sequence genes. METHODS: In this study, we conducted a LAMP assay for leprosy and compared it with quantitative polymerase chain reaction (q-PCR) and conventional PCR assays to determine the efficiency, sensitivity and specificity of each technique. We chose conserved sequence RLEP as a suitable molecular target for assays. RESULTS: The LAMP assay provided rapid and accurate results, confirming leprosy in 91/110 clinical skin tissue samples from leprosy patients and amplifying the target pathogen in <60 min at 65 °C. The assay was more sensitive than conventional PCR and more straightforward and faster than the q-PCR assay. CONCLUSIONS: The LAMP assay has the potential for developing quicker, more accessible visual methods for the detection of M. leprae, which will enable early diagnosis and treatment and prevent further infection in endemic areas.

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 of county-level strain diversity, distribution, and transmission patterns of leprosy in endemic provinces of China. METHODS: We genetically characterized 290 clinical isolates of M. 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 the discriminatory index, (GTA)9, (AT)17, (AT)15, (TA)18, (TTC)21, and (TA)10 are reported to be more 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) counties of Hunan, and Zhijin (N = 3), Anlong (N = 2), Zhenning (N = 2), and Xixiu (N = 2) counties of Guizhou. In some clusters, people's social relations have been observed between villages. From the 290 clinical isolates, the most predominantly reported SNP was 3K (278, 95.8%), followed by SNP 1D (10, 3.4%), which are typically observed to be predominant in China. We also detected the novel SNP 3J (2, 0.8%), which has not yet been reported in China. CONCLUSION: The clustering pattern of M. leprae indicates the transmission of leprosy still persists at county levels, suggesting that there is a need to implement better approaches for tracing the close contacts of leprosy patients.