title: Molecular Evidence for the Aerial Route of Infection of Mycobacterium leprae and the Role of Asymptomatic Carriers in the Persistence of Leprosy.
abstract: BACKGROUND
  Leprosy persists as a public health problem. The chain of transmission and mechanism of infection are not completely understood. In the current study, we investigated the route of infection and of disease onset, from airway exposure, colonization, and bloodstream dissemination.
  
  
  METHODS
  Mycobacterium leprae DNA was detected through quantitative polymerase chain reaction in nasal vestibule, nasal turbinate mucosa, and peripheral blood samples, along with anti-phenolic glycolipid I serology and skin tests from the same individual, from 113 leprosy patients and 104 household contacts of patients (HHCs). Bivariate statistics and multiple correspondence analysis were employed.
  
  
  RESULTS
  The rates of DNA positivity among patients were 66.4% (75 of 113) for nasal swab samples, 71.7% (81 of 113) for nasal turbinate biopsy samples, 19.5% (22 of 113) for blood samples, with seropositivity of 62.8% (71 of 113 samples) and with increasing incidences toward the multibacillary pole of the clinical spectrum. Positivity among HHCs were as follows: 49% (51 of 104) for nasal swab samples, 53.8% (56 of 104) for nasal biopsy samples, 6.7% (7 of 104) for blood samples, and 18.3% (19 of 104 samples) for anti-phenolic glycolipid I serology. During the follow-up of 5-7 years, out of 104 HHCs, 7 developed leprosy (6.7%). Risk for the disease outcome was estimated by comparing results in HHCs who develop leprosy with those not affected. Neither nasal passage nor mucosa positivity was determinant of later disease onset; however, blood presence increased the risk for disease development (relative risk/positive likelihood ratio, 5.54; 95% confidence interval, 1.30-23.62), as did seropositivity (positive likelihood ratio, 3.69 [1.67-8.16]; relative risk, 5.97 [1.45-24.5]).
  
  
  CONCLUSIONS
  Our findings strongly suggest that the aerosol route of infection and transmission is predominant and that HHCs contribute to the infection risk to themselves and probably to others.
authors: National Reference Center for Sanitary Dermatology and Leprosy, Clinics Hospital.|Postgraduate Program in Health Sciences, School of Medicine.
authors: Sergio
authors: S
authors: Araujo
authors: National Reference Center for Sanitary Dermatology and Leprosy, Clinics Hospital.
authors: Larissa Oliveira
authors: LO
authors: Freitas
authors: National Reference Center for Sanitary Dermatology and Leprosy, Clinics Hospital.|Postgraduate Program in Health Sciences, School of Medicine.|Institute of Biochemistry and Genetics, Federal University of Uberlandia, Minas Gerais, Brazil.|Department of Medical Microbiology and Immunology, University of California, Davis.
authors: Luiz Ricardo
authors: LR
authors: Goulart
authors: National Reference Center for Sanitary Dermatology and Leprosy, Clinics Hospital.|Postgraduate Program in Health Sciences, School of Medicine.
authors: Isabela Maria Bernardes
authors: IM
authors: Goulart
mesh_terms: D000293:Adolescent; D000328:Adult; D000336:Aerosols; D000907:Antibodies, Bacterial / Q000097:blood; D000942:Antigens, Bacterial / Q000276:immunology; D058345:Asymptomatic Infections; D058491:Bacterial Load; D001706:Biopsy; D002353:Carrier State / Q000453:epidemiology / Q000382:microbiology*; D004269:DNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D005191:Family Characteristics; D005260:Female; D005500:Follow-Up Studies; D006017:Glycolipids / Q000276:immunology; D006801:Humans; D007918:Leprosy / Q000097:blood / Q000453:epidemiology / Q000382:microbiology* / Q000635:transmission*; D008297:Male; D008875:Middle Aged; D009166:Mycobacterium leprae / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D009297:Nasal Mucosa / Q000382:microbiology*; D009666:Nose / Q000382:microbiology; D016133:Polymerase Chain Reaction
chemical_list: D000336:Aerosols; D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D004269:DNA, Bacterial; D006017:Glycolipids; C045169:phenolic glycolipid I, Mycobacterium leprae
keywords: Epidemiology; Leprosy; Mycobacterium leprae; Quantitative Real-Time PCR; phenolic glycolipid I