M. tuberculosis DNA detection in nasopharyngeal mucosa can precede tuberculosis development in contacts.

BACKGROUND: The nasopharynx is a known gateway for some mycobacterial species such as Mycobacterium bovis and M. leprae. M. tuberculosis can cross lymphoepithelial barriers in vitro, but its ability to colonise the nasopharyngeal mucosa in vivo has not been established. OBJECTIVE: To determine if M. tuberculosis can be transiently detected in nasopharyngeal mucosa of tuberculosis (TB) contacts as a preliminary step in the development of tuberculous infection. DESIGN: Exploratory study conducted among asymptomatic household contacts of pulmonary TB cases. A chest X-ray, QuantiFERON(®) TB-Gold or tuberculin skin test and a bilateral nasopharyngeal swab for Xpert(®) MTB/RIF and mycobacterial culture were performed at baseline and repeated 8-12 weeks later. RESULTS: Eighty-nine contacts were enrolled a median of 9 days after the diagnosis of the index case. At baseline, 29.9% were positive for latent tuberculous infection and one subject (1.1%) had a positive Xpert in the nasopharyngeal swab with a normal chest X-ray, negative QuantiFERON and negative induced sputum. After 12 weeks' follow-up, this subject developed a new cough and upper lobe infiltrates and M. tuberculosis grew in sputum. No other cases of active TB were detected at follow-up. CONCLUSION: The detection of M. tuberculosis DNA in the nasopharyngeal mucosa of contacts is an infrequent event that in this instance preceded the development of pulmonary TB. Its pathogenic role requires further investigation.

Risk factors for developing leprosy--a population-based cohort study in Indonesia.

We identified risk factors associated with increased yearly incidence rates of leprosy in five island populations. Age, sex, household size and Mycobacterium leprae-specific antibodies as well as contact factors were studied. Of 94 index patients (patients diagnosed in 2000), 43 (46%) were classified as multibacillary (MB), 17 (19%) were seropositive for PGL-1 [corrected] antibodies and 6 (7%) had M. leprae DNA in nasal swabs as determined by polymerase chain reaction (PCR) testing. All PCR positive patients were also seropositive. Forty-four of 4903 initially symptom free persons developed leprosy within 4 years, giving an incidence rate of 298 per 1000 person-years. Men had a 22 times higher risk [95% confidence interval (CI): 1.2-4.1] of developing leprosy than women. People living in households with more than 7 members had a 3.1 times higher risk (95% CI: 1.3-7.3) than households of 1-4 members. Persons who were seropositive in 2000 had a 3.8 times higher risk (95% CI: 1.1-12.6) than seronegative persons. Household contacts of MB patients had an adjusted hazard ratio (aHR) of 4.6 (95% CI: 1.6-12.9) and household contacts of PCR positive patients an aHR of 9.36 (95% CI: 2.5-34.9) compared with non-contacts. Patients with PCR positive nasal swabs, suggesting nasal excretion of M. leprae, are probably the patients with the highest transmission potential. Since all index patients who were PCR positive were also seropositive, serology seems an adequate tool to identify these patients. Preventing seropositive persons from becoming seropositive and infectious patients might break the chain of transmission.