RESUMO
A recent advance in molecular typing for tracing the transmission of leprosy is the discovery of short tandem repeats (STRs) in Mycobacterium leprae. To substantiate polymorphic loci from STR as promising candidates for molecular typing tools in leprosy epidemiology, 44 STR loci including 33 microsatellites and 11 minisatellites were investigated among 27 laboratory strains by sequencing PCR products. Not all STRs were necessarily polymorphic. Thirty-two out of the 44 loci were polymorphic. Nine polymorphic loci were suitable for identifying genotypes according to the discriminatory capacity, stability, and reproducibility. All the strains were classified into independent genotypes by the selected nine loci. Three multi-case households were subjected to molecular typing. M. leprae obtained from household cases showed identical copy numbers by TTC triplet alone, but the isolates from one family contact case were divided into different genotypes by adding eight other polymorphic loci. The combination of information from multiple loci allows increasing levels of discrimination and it is likely that the generation and documentation of data will result in the choice of a potential molecular typing tool for leprosy epidemiology.
Assuntos
Camundongos , Humanos , Animais , Análise de Sequência de DNA , Camundongos Endogâmicos BALB C , Camundongos Nus , DNA Bacteriano , Hanseníase , Marcadores Genéticos , Mycobacterium leprae , Pé , Repetições Minissatélites , Repetições de Microssatélites , Sequências de Repetição em Tandem , Técnicas de Tipagem Bacteriana , Variação GenéticaRESUMO
The genotypes of Mycobacterium leprae isolates originating from Mexico, Peru and Paraguay were analysed for the polymorphism of short tandem repeats in the rpoT gene. The genotype with four copies of the six-base tandem repeats in the rpoT gene was prominently predominant in Mexico, but the genotype of all isolates from Peru and Paraguay contained three copies of the six-base tandem repeats. These obvious different distributions might reflect the spread of leprosy by the different strains of M. leprae harboured by the various human races that moved to the American continent, as has been demonstrated in other infectious diseases.
Assuntos
Proteínas de Bactérias/genética , Hanseníase/microbiologia , Hanseníase/transmissão , Mycobacterium leprae/genética , Polimorfismo Genético , Fator sigma/genética , Humanos , Hanseníase/epidemiologia , México/epidemiologia , Mycobacterium leprae/isolamento & purificação , Paraguai/epidemiologia , Peru/epidemiologiaRESUMO
Serological methods have been used for detecting infection with Mycobacterium leprae. We have applied a serological test to explore the possibility it could detect a bacterial relapse among patients who have been cured with chemotherapy. More specifically we used an indirect enzyme-linked immunosorbant assay (ELISA) using the natural disaccharide (ND) of the phenolic glycolipid antigen of M. leprae linked to bovine serum albumin as antigen. Antibody levels were measured in sera from normal controls, active leprosy cases, cured leprosy patients, and relapsing leprosy patients. We correlated antibody levels with the type of leprosy, the bacterial index, and with relapse among cured leprosy patients. In our hands, the ND-ELISA, when applied to screening for infection with M. leprae, had excellent sensitivity, specificity, positive and negative predictive values, and both a low false positive rate and a low false negative rate. Antibody levels gradually increased among active patients from the tuberculoid to the lepromatous end of the leprosy spectrum. There was a year-by-year fall in antibody levels in patients responding to chemotherapy. Antibody levels and the bacterial index were correlated using the Spearman's rank correlation method. Serial antibody levels were measured in 666 leprosy patients after being cured with dapsone monotherapy. Over a three year follow up, 95 multibacillary patients became antibody positive and 12 of them had bacterial relapses of their disease. In contrast, among 335 cases that remained antibody negative, only one relapse was seen. Among 44 paucibacillary cured patients who became antibody positive, there was one relapse. There were 192 such patients who remained antibody negative and one relapsed. The risk of relapse is 6.7 times higher among cured multibacillary patients compared to cured paucibacillary patients. Overall, the cumulative relapse rate among antibody positive cases was 13.7%, compared to 0.4% among antibody negative patients. We conclude that the ND-ELISA is a useful tool both for screening for early infection with M. leprae and for predicting a relapse in cured patients, particularly in cured multibacillary patients.