Presence of viable Mycobacterium leprae in environmental specimens around houses of leprosy patients

PURPOSE

Leprosy is a chronic systemic infectious disease caused by Mycobacterium leprae, one of the first organisms to be established as the cause for disease in humans. Because of high prevalence pockets of leprosy in the endemic regions, it is necessary to identify the possible sources of M. leprae in the environment and its mode of transmission.

MATERIALS AND METHODS

Slit skin smears (SSSs) from lesions were collected in 70% ethanol from 50 leprosy cases staying in the leprosy resettlement village and hospital from a high endemic area. One hundred and sixty soil samples were collected from different areas around the leprosy hospital and from the resettlement village of cured leprosy patients where active cases also resided at the time of sample collection. M. leprae specific gene region (RLEP 129 bp) and 16S rRNA targets were used for polymerase chain reaction (PCR) based detection for the presence and viability of M. leprae. An rpoT region was also amplified to determine presence of numbers of 6 bp tandem repeats.

RESULTS

All the SSS samples collected from patients showed three copies of rpoT region (6 bp tandem repeat, an ancient Indian type). Fifty-two soil samples showed presence of M. leprae DNA whereas M. leprae specific 16S rRNA gene was amplified in sixteen of these samples. PCR amplification and fragment length analysis showed 91 bp, i.e., three copies of the rpoT 6 bp tandem repeats from soil samples and similar three copies observed in patient samples.

CONCLUSION

Presence of viable M. leprae in the soil having same rpoT genotype of M. leprae noted in patients suggests that it could be the same strain of M. leprae. M. leprae found in the soil could be the one that is excreted out by the patient. Significance of its viability in the environment and its pathogenicity with respect to transmission needs to be further explored. Findings of this study might provide possible insights for further exploration into understanding transmission patterns in leprosy and also will throw light on identifying potential for existence of extra human source or reservoirs of M. leprae, if any.

Single nucleotide polymorphism-based molecular typing of M. leprae from multicase families of leprosy patients and their surroundings to understand the transmission of leprosy

The exact mode of transmission of leprosy is not clearly understood; however, many studies have demonstrated active transmission of leprosy around a source case. Families of five active leprosy cases and their household contacts were chosen from a high endemic area in Purulia. Fifty-two soil samples were also collected from different areas of their houses. DNA was extracted from slit-skin smears (SSS) and soil samples and the Mycobacterium leprae-specific RLEP (129 bp) region was amplified using PCR. Molecular typing of M. leprae was performed for all RLEP PCR-positive samples by single nucleotide polymorphism (SNP) typing and confirmation by DNA sequencing. SSS of these five patients and six out of the total 28 contacts were PCR positive for RLEP whereas 17 soil samples out of 52 showed the presence of M. leprae DNA. SNP typing of M. leprae from all RLEP PCR-positive subjects (patients and smear-positive contacts) and 10 soil samples showed the SNP type 1 genotype. M. leprae DNA from the five leprosy patients and the six contacts was further subtyped and the D subtype was noted in all patients and contacts, except for one contact where the C subtype was identified. Typing followed by subtyping of M. leprae clearly revealed that either the contacts were infected by the patients or both patients and contacts had the same source of infection. It also revealed that the type of M. leprae in the soil in the inhabited areas where patients resided was also of the same type as that found in patients.

Single nucleotide polymorphisms typing of Mycobacterium leprae reveals focal transmission of leprosy in high endemic regions of India

Earlier studies indicate that genotyping of Mycobaterium leprae based on single-nucleotide polymorphisms (SNPs) is useful for analysis of the global spread of leprosy. In the present study, we investigated the diversity of M. leprae at eight SNP loci using 180 clinical isolates obtained from patients with leprosy residing mainly in Delhi and Purulia (West Bengal) regions. It was observed that the frequency of SNP type 1 and subtype D was most predominant in the Indian population. Further, the SNP type 2 subtype E was noted only from East Delhi region and SNP type 2 subtype G was noted only from the nearby areas of Hoogly district of West Bengal. These results indicate the occurrence of focal transmission of M. leprae infection and demonstrate that analysis by SNP typing has great potential to help researchers in understanding the transmission of M. leprae infection in the community.

Cortisol and proinflammatory cytokine profiles in type 1 (reversal) reactions of leprosy

PURPOSE

Cortisol levels in the circulation and at the sites of peripheral inflammation regulate type 1 (Reversal) reactions in leprosy akin to delayed type hypersensitivity reactions (DTH). In this study we determine the extent to which the differential mRNA expression of genes encoding cortisone-cortisol shuttle enzymes (11 β hydroxysteriod dehydrogenase I & II (11 β HSD I & II)), circulatory levels of proinflammatory cytokines (IL-6, IL-7, IP-10, IL-17F, IL-23, TNF-α, IL-1β, PDGF BB and CRP) and cortisol are associated with development of type 1 reactions in leprosy.

METHODS

Urine, blood and incisional skin biopsy samples from site of lesions were collected from 49 newly diagnosed untreated leprosy cases in T1R and 51 cases not in reaction (NR). mRNA expression levels of genes encoding 11 β HSD I & II in skin biopsy samples were determined by realtime PCR. Cortisol levels from the lesional skin biopsies, serum and urine samples and serum proinflammatory cytokine levels were measured using ELISA.

RESULTS

The mean expression ratios of 11 β HSD I & II are significantly lower in leprosy cases with T1R when compared to the NR leprosy cases. Cortisol levels in lesional skin biopsies and in urine are significantly lower (p=0.001) in leprosy cases with T1R. Serum cytokine levels of IP-10, IL-17F, IL-IL-6 and TNF-α are significantly higher (p<0.05) in leprosy cases with T1R when compared the NR leprosy cases.

CONCLUSION

Our study indicated an association of urinary and lesional skin cortisol levels with the manifestation of T1R in leprosy. IP-10, IL-17F, IL-6 and TNF-α can be potential prognostic serological markers and gene expression markers for early detection of type 1 reactions in leprosy.

Cohort study of the seasonal effect on nasal carriage and the presence of Mycobacterium leprae in an endemic area in the general population

Leprosy continues to be a significant health problem in certain pockets in developing countries. Better understanding of the transmission and source of the infection would help to decipher the transmission link, leading to control of the spread of the disease. The nose is considered to be a portal of entry, suggesting an aerial route for transmission through droplet infection. The evidence suggests that many individuals from endemic countries carry Mycobacterium leprae in their nasal cavities without having obvious symptoms of leprosy. The objective of the present study was to assess the presence of M. leprae on the nasal mucosa in the general population from a leprosy-endemic pocket. M. leprae detection was carried out using PCR targeting RLEP. Four hundred subjects from an area highly endemic for leprosy were included in the study and followed up during three different seasons--winter, summer, and monsoon--for evidence of nasal exposure to M. leprae. PCR positivity for M. leprae was observed in 29%, 21% and 31% of the samples collected in winter, summer and the monsoon season, respectively. Twenty-six individuals from the cohort showed amplification for M. leprae for all seasons. Our results are consistent with reports in the literature showing widespread exposure to M. leprae in the endemic community. The results also suggest possible association of the environmental conditions (climate) with the transmission pattern and levels of exposure to M. leprae. However, the present study indicated that the population from highly endemic pockets will have exposure to M. leprae irrespective of season.