Detection ofMycobacterium lepraein nasal mucosa biopsies by the polymerase chain reaction

Abstract

Several discoveries about leprosy indicate that Mycobacterium leprae transmission mainly occurs by inhalation, and the nose is major port of entry and exit. The present study evaluated the clinical application of PCR for detection of M. leprae DNA in nasal mucosa biopsies in untreated leprosy patients (52) and their contacts (99) from the State Reference Center in Sanitary Dermatology and Leprosy, Uberlandia, MG, Brazil. PCR detection of a 372-base pair DNA fragment from M. leprae was accomplished in 36 (69.2%) patients, from which 34 (91.9%) of them were multibacillaries. Furthermore, PCR was positive in 3 (16.7%) of 18 slit-skin smear negative, 4 (25.0%) of 16 skin lesion BI negative, 8 (33.3%) of 24 nasal mucosa BI negative patients, and 10 of 99 contacts (10.1%). The presence of bacilli in 10.1% of the contacts may potentially reflect an occult leprosy, and these patients must be accompanied, followed by a chemoprophylaxy treatment. Considering all PCR results against clinical and BI classification of patients and controls, we have found a sensitivity of 69.2%, a specificity of 89.9%, and an accuracy of 82.8%. It has been demonstrated here through PCR of nasal biopsies that the bacillus invades the mucosa, passing through the nasal inferior turbinate to reach peripheral blood. Therefore, the molecular investigation of invasive nasal biopsies by PCR tests has proven to be useful in defining patients of higher risk of transmission and risk-group contacts, which is an important step to reach the World Health Organization objective towards the elimination of leprosy as a public health problem.

Unveiling healthy carriers and subclinical infections among household contacts of leprosy patients who play potential roles in the disease chain of transmission

“…Among HHCs of LPs, 4.7% tested positive for M. leprae DNA in nasal swabs, similar to the percentages of (80) 1 (20) positive results observed among TT or BT patients, but only half of the percentage observed in nasal biopsies of PB patients described elsewhere (Patrocínio et al 2005). This previous finding led us to the following hypothesis regarding the infection route: the bacillus invades the mucosa, passing through the nasal inferior turbinate and through the peripheral blood (Patrocínio et al 2005), eventually reaching Schwann cells and the mononuclear phagocytic system (Harboe 1985).…”

“…The anti-PGL-I serology was strongly correlated with the MB OC and associated CFs of leprosy, indicating a possible active infection, as shown elsewhere (Cho et al 2001, Martinez et al 2011. However, the presence of M. leprae DNA in nasal swabs has been used as an epidemiological tool to understand the role of both patients and contacts in the complex transmission chain (Hatta et al 1995, Beyene et al 2003, Patrocínio et al 2005, Job et al 2008.…”

“…This previous finding led us to the following hypothesis regarding the infection route: the bacillus invades the mucosa, passing through the nasal inferior turbinate and through the peripheral blood (Patrocínio et al 2005), eventually reaching Schwann cells and the mononuclear phagocytic system (Harboe 1985). Therefore, these findings suggest that contacts may be exposed to a source of infection who harbours bacilli in the nose even for a short period of time because nasal biopsies detect 14% more positive test results than do nasal swabs (Patrocínio et al 2005). Due to the complex relationships among genetic, immunological and environmental factors, most of the contacts will not become infected or develop leprosy (Goulart & Goulart 2009).…”

“…The upper respiratory tract is considered the main portal for the entry and exit of M. leprae (Patrocínio et al 2005, Martinez et al 2011) and individuals with active disease (MB patients in particular) are the main sources of infection (Job et al 2008). Because M. leprae is an obligate intracellular pathogen and there is little evidence of non-human reservoirs in endemic countries, it is most likely that leprosy spreads from person to person.…”

Deteccção do DNA de Mycobacterium leprae em secreção nasal

“…O PCR demonstra ser um método de diagnóstico promissor na mensuração da infecção subclínica. Provavelmente, um número de indivíduos infectados definidos como assintomáticos existe e devem ter função ativa na transmissão da doença (18) . Essa proposição foi visualizada nos resultados obtidos neste estudo, no momento em que foi revelada alta positividade nas amostras de secreção nasal (P<0.0000).…”