Molecular epidemiology of Mycobacterium tuberculosis in Madang, Papua New Guinea

Molecular epidemiology of Mycobacterium tuberculosis in Madang, Papua New Guinea
In 2010, TB was estimated to have caused 8.8 million incident cases and more than 1.4 million deaths worldwide. The TB-HIV co-epidemic and the development of drug resistances are major challenges for TB control programs. The long duration of anti-TB therapies and the limited treatment options led to the emergence of drug-resistant Mycobacterium tuberculosis strains in virtually all regions of the world. Estimates indicated that in 2009, about 3.3% of all new TB patients worldwide had MDR-TB.
PNG belongs to the seven countries in the Western Pacific region with the highest estimated TB burden. Yet, very scarce information is available about the characteristics of the circulating M. tuberculosis population in this country. On the basis of a tight collaboration between the Swiss TPH and the PNG IMR, this project was set up to initiate long term TB investigations in PNG.
M. tuberculosis isolates from pulmonary TB patients in Madang and surroundings were characterized with focus on drug resistance and strain genotypes. Apart from the molecular analyses conducted mainly in Switzerland, this project also aimed at transferring to PNG some technical knowledge necessary for the improvement of TB control in that region.
M. tuberculosis isolates were collected during a pilot study conducted in 2005-2007 and in the frame of an ongoing treatment cohort study initiated in 2009. DST indicated substantial rates of drug resistance, further confirmed by the presence of specific resistance-conferring mutations; in particular, 5.2% MDR-TB was observed. SNP-based genotyping showed that out of the six M. tuberculosis lineages described worldwide, the strains from Madang and surroundings predominantly belonged to the Euro-American and East-Asian lineages (Lineage 4 and Lineage 2, respectively). Furthermore, Lineage 2 strains were significantly associated with drug resistance. Molecularly clustered strains were identified using a combination of two discriminatory genotyping methods and suggested evidence for patient-to-patient M. tuberculosis transmission, including transmission of drug-resistant strains.
This study provides the first molecular description of the M. tuberculosis strains circulating in the Madang area of PNG. Nevertheless, to elucidate the burden of TB at the country-level, further studies taking into account several locations throughout PNG are needed.