Novel PCR primers for improved detection of Mycobacterium leprae and diagnosis of leprosy.

AIMS: Diagnosis of leprosy, a chronic infection caused by Mycobacterium leprae, predominantly depends on clinical manifestations and histopathological analysis, hampering rapid and accurate diagnostics. Our aim was to increase accuracy of leprosy diagnosis by improving M. leprae's DNA detection based on polymerase chain reaction (PCR) technique using new specific primers for the RLEP repetitive sequence. METHODS AND RESULTS: The specific target region, RLEP, of M. leprae's genome was selected based on comparative genomics. After confirming the specificity of this region, using blastn analysis, primers were designed and tested for their in silico specificity. To evaluate the specificity and sensitivity of these primers in vitro, 184 blood samples from patients were used in qPCR. The new primer pair LYON1/LYON2 produced 91% positive samples, whereas the current primer pair LP1/LP2 produced 46%. Specificity and DNA detection limit test were carried out to compare the efficiency of the developed primer pair. The LYON1/LYON2 primer showed 100% specificity, whereas LP1/LP2 showed 64%. The DNA detection limit of LYON1/LYON2 was 10 copies of bacterial genomes per millilitre, whereas LP1/LP2 was 1000 copies of bacterial genomes per millilitre. CONCLUSIONS: In conclusion, the developed LYON1/LYON2 primer pair presented to be a specific and sensitive new molecular marker for the diagnosis of leprosy. SIGNIFICANCE AND IMPACT OF THE STUDY: The development of a specific primer pair for the detection of the M. leprae genome through qPCR technique contributes to a fast, sensitive and specific diagnosis, which is essential to prevent spreading and progression of this disease.

Early detection of M. leprae by qPCR in untreated patients and their contacts: results for nasal swab and palate mucosa scraping.

To verify if the hard palate mucosa can be a site of relevance in the early molecular detection of Mycobacterium leprae in leprosy cases and their household contacts and if there is a correlation of results in nasal swab with those of the scraping of the palate mucosa. The quantitative polymerase chain reaction technique was used. Sample included 78 patients with untreated leprosy (G1), their 54 household contacts (G2), and 80 healthy individuals for the negative control (G3). The presence of M. leprae in both G1 and G2 was observed with the nasal swab and the palate mucosa scrapings methods, and it was shown that the sensitivity between the qPCR exams for RLEP and 85B genes is equivalent, with no statistically significant differences (G1 positivity of 35% in the hard palate mucosa and 44% for the nasal one, p = 0.3731 and for G2 of 31 and 38%, respectively, p = 0.6774). Results support the fact that the buccal mucosa and nasal mucosa may be important sites of primary infection of leprosy with repercussion in the transmission chain and that asymptomatic household contacts are heavily harbored by the causative agent of leprosy, which has a critical significance in the prevention and control action of this disease, since the evaluation of these sites arises as of importance in the early detection of M. leprae. Close monitoring and chemoprophylaxis of household contacts appear to be critical to attain interruption of the transmission of leprosy in endemic countries.

Application of RLEP real-time PCR for detection of M. leprae DNA in paraffin-embedded skin biopsy specimens for diagnosis of paucibacillary leprosy.

The TaqMan real-time polymerase chain reaction (PCR) assay was evaluated systematically with respect to the standard curve, linear range, and used for detecting Mycobacterium leprae DNA in paraffin-embedded skin biopsy specimens from 60 confirmed leprosy patients and three healthy individuals and 29 other dermatoses and bacterial DNA from 21 different species. The test was further evaluated with 51 paucibacillary (PB) patients. The results showed that the test had good sensitivity (8 fg) and good specificity with no cross-reactivity with 21 other bacterial species and the control specimens, except one with Xanthomatosis. The real-time PCR detection rate for the 51 PB specimens was 74.5% (38 of 51). We conclude that the real-time PCR test is a useful adjunct test for diagnosing early stage or PB leprosy cases.