RESUMEN
The relevance of bacterial index (BI) for understanding the prognosis of leprosy patients on treatment has been extensively debated, as it does not give a very clear idea of the viability of the bacteria in patients under treatment. Here we used slit-skin smear samples of leprosy patients to test the suitability for studying viability of Mycobacterium leprae using reverse transcription polymerase chain reaction (RT-PCR). For this purpose, we recruited 13 multibacillary (MB) leprosy patients (8 lepromatous and 5 borderline lepromatous). Of these, 7 were relapse cases, 3 were under treatment (MB-MDT), 2 were new cases and 1 had completed treatment. We carried out extraction of RNA using Trizol reagent (Life Technologies, UK) from the slit-skin smear samples from these patients. The RNA preparation was then used for the RT-PCR using Mycobacterium leprae-specific primers for the fragment of 16s ribosomal RNA gene. Samples from both the new cases, 4 suspected relapse cases and 1 patient under treatment showed positive RT-PCR results. Other 6 patients whose smear samples did not show any amplification by RT-PCR were on MB-MDT from 8 to 30 months. The usefulness of the technique needs to be validated using mouse footpad technique and also should be more extensively explored for studying the viability of M. leprae, the efficacy of treatment and the presence of other mycobacteria in the slit-skin smear samples.
Asunto(s)
Lepra Dimorfa/microbiología , Lepra Lepromatosa/microbiología , Mycobacterium leprae/aislamiento & purificación , Adulto , Anciano , Electroforesis en Gel de Agar , Femenino , Humanos , Masculino , Persona de Mediana Edad , Mycobacterium leprae/genética , ARN Bacteriano/química , ARN Bacteriano/genética , ARN Ribosómico 16S/química , ARN Ribosómico 16S/genética , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
Recent advances in treatment have achieved a large drop in the prevalence of active leprosy cases, but the incidence is at best decreasing slowly. Most people within leprosy-endemic populations have been exposed to Mycobacterium leprae, but few develop disease and it seems likely that the majority of the population develops protective immunity. If the site of initial infection is in the nose, dissemination of bacilli around the body to skin and nerve implies that the initial infection is bacilliferous and it has been shown that nasal M. leprae are detectable by polymerase chain reaction (PCR) of nasal swabs. Since salivary anti-M. leprae IgA (sMLIgA) levels are correlated with protection, we have surveyed groups of leprosy patients, contacts and the general population for both their sMLIgA and nasal PCR positivity. A total of 304 subjects were enrolled in the study: PCR and mucosal challenge tests were performed in 204 of these individuals. sMLIgA was present in 66% of treated patients, 76% of leprosy workers and 72% of healthy contacts. However, only 33% of indigenous subjects were sMLIgA+, in contrast to the earlier studies showing 74% positivity. PCR for M. leprae was present in both household contacts (2%) and indigenous controls (5%). In a subsequent follow-up study, nasal swabs were taken from 97 of those studied in the first series: three PCR+ individuals followed up after one year became negative, while of the remaining 94 PCR- individuals retested, 2 became positive. Of 112 subjects retested with the mucosal challenge test for sMLIgA: 22 converted from positive to negative and 12 from negative to positive. These results suggest that there is widespread subclinical transmission of M. leprae with transient infection of the nose resulting in the development of a mucosal immune response, despite the fact that few individuals will develop clinical disease. This may explain the current lack of effect of multidrug therapy (MDT) control programmes on incidence, although the reduction in general population immunity is consistent with some effect of MDT on transmission.
Asunto(s)
Inmunidad Mucosa , Lepra/inmunología , Lepra/transmisión , Adolescente , Adulto , Anciano , Anticuerpos Antibacterianos/análisis , Ensayo de Inmunoadsorción Enzimática , Femenino , Humanos , Inmunoglobulina A/análisis , Lepra/microbiología , Masculino , Persona de Mediana Edad , Mycobacterium tuberculosis/inmunología , Mycobacterium tuberculosis/aislamiento & purificación , Mucosa Nasal/microbiología , Reacción en Cadena de la Polimerasa , SalivaRESUMEN
Skin lesions of leprosy that are anaesthetic, well defined, limited in number and dry with significant hair loss generally fit into the paucibacillary (PB) spectrum. The bacteriological index (BI) is expected to be negative or low. We have reported a case who presented with such findings but whose BI readings were high. Together with the biopsy findings the patient was classified as having borderline (BL) leprosy. The role of the skin smear examination and the misleading nature of some clinical features are highlighted. The authors feel that skin smear examinations should be performed on all leprosy patients at the time of diagnosis.