Oral mucosa as a source of Mycobacterium leprae infection and transmission, and implications of bacterial DNA detection and the immunological status

Abstract

Leprosy is an important health problem in Brazil despite extensive use of multidrug therapy. The nasal mucosa is the preferential site of entry and exit of Mycobacterium leprae, and although lesions have been found in the oral mucosa, its potential involvement in the transmission of leprosy bacilli has never been investigated. We investigated the presence of the M. leprae DNA in buccal swabs of leprosy patients (334) and household contacts (1288) through polymerase chain reaction (PCR), and correlated this with clinical and laboratorial evaluations. The overall positivity for patients and contacts was 18.26% and 6.83%, respectively. Subclinical infection among contacts was considered when PCR and anti-PGL-1 ELISA presented positive results. This study provides evidence that the oral mucosa may be a secondary site of M. leprae transmission and infection, and contacts with bacillary DNA may be actively involved in transmission. We have also shown that bacilli DNA is more frequently found in the oral mucosa of PB patients. Our findings have great epidemiological relevance and indicate an additional strategy for leprosy control programmes and dental clinics.

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

“…However, they may spread M. leprae to susceptible individuals and this may be a plausible mode of transmission. Our results also corroborate previous studies that have detected M. leprae DNA in the nasal mucosa of endemic populations (Hatta et al 1995, Beyene et al 2003, Martinez et al 2011, regardless of the OC and CFs of their ICs. Our results revealed a linear correlation between bacillary DNA levels and the CFs of the patients' diseases.…”

“…The result of each test alone has special clinical significance. 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.…”

“…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.…”

Factors associated with seropositivity for APGL-Iamong household contacts of leprosy patients

“…As suggested in the literature, indeterminate leprosy is the initial clinical manifestation of a recent infection, when an immune-cellular specifi c response against M. leprae is dubious. These results suggest that some of these cases could evolve into MB forms, thus favoring household transmission, as described by Martinez et al (21) . Conversely, there is a possibility of other occult MB cases in the same house, leading to exposure to the bacilli and a high probability of subclinical infection among these HC.…”

Presence of Mycobacterium leprae DNA and PGL-1 antigen in household contacts of leprosy patients from a hyperendemic area in Brazil

“…The combination of molecular and serological techniques, such as polymerase chain reaction (PCR), phenol-glycolipid-1 antigen (anti-PGL-1) enzyme-linked immunosorbent assay (ELISA), and the ML-Flow test, have shown good efficacy in leprosy diagnosis Job et al, 2008;Stefanni, 2008;Martinez et al, 2011). Additionally, contacts of leprosy patients that are positive for anti-PGL-1 have a 6-fold higher risk of illness compared to healthy individuals (Goulart et al, 2007).…”