Molecular epidemiology of tuberculosis in selected sites across Papua New Guinea

With an estimated one third of the global population being infected with latent tuberculosis (TB) and 8.6 million people developing active TB in 2012, this infectious disease remains a major global health concern. Increasing drug resistance (DR) and the HIV pandemic are further challenges to the control of the disease. Mycobacterium tuberculosis (Mtb) is responsible for most of the TB cases in humans. For a long time it was thought that only environmental factors and the host immune status are the driving forces of TB transmission. Recently, evidence of the influence of the bacterial genetic background on transmission and disease outcome is increasing. Clinical samples from around the globe are required to further analyze the impact of the complex interactions of drug resistance, bacterial and host genetics, as well as environmental and social factors on TB epidemiology and individual patient management. Even though Papua New Guinea (PNG) is one of the high TB burden countries in the South Pacific, not much data on the local epidemiology of TB exists. Apart from the urgent need to fill such evidence gaps, the country also provides an interesting platform for TB research, considering its population genetic diversity and its isolation in the past. The presented project aimed at providing baseline data about the molecular epidemiology of tuberculosis from specific sites in PNG, including drug resistance and the population structure of Mtb. Between July and December 2010, active TB case detection surveys were conducted in the catchment area of two health centres in PNG: around Sausi health centre in Madang Province and around East-Cape health centre in Milne Bay Province. Each household in the catchment area was screened for people with chronic productive cough aged 15 years and above. Of household members with chronic productive cough not having received TB treatment yet, three sputum samples were collected. Subsequently, samples were analysed by light microscopy to diagnose pulmonary TB by detecting the presence of acid fast bacilli. Around Sausi, 24 so far undetected pulmonary TB cases were identified, whereas in East-Cape only one additional case was found, reflecting the differences in the performance of the control program between different sites in PNG. Active case detection as a complementary case detection approach turned out to be a useful tool to increase the case detection rate in certain areas, but appeared unsuitable to investigating the prevalence of drug resistance and the genetic background of Mtb. However, operational limitations did not allow obtaining better estimates on the real burden of TB in the country in the frame of our study. From November 2010 to July 2012, passive case detection was conducted in three provincial hospitals of PNG: Modilon General Hospital in Madang Province, Goroka General Hospital in Eastern Highlands Province and Alotau Provincial Hospital in Milne Bay Province. Three sputum samples were collected from TB suspects aged 15 years and above and subsequently analysed by light and fluorescent microscopy. Furthermore, the level of drug resistance as well as the genetic background of M. tuberculosis strains was determined and findings compared between sites. Of 225 passive case detection samples grown in culture, 212 samples could successfully be tested for drug susceptibility. Overall, 10.8% (23/212) strains were found to be resistant to at least one of the first-line drugs streptomycin, rifampicin, isoniazid, pyrazinamide or ethambutol. Differences between study sites in any type of DR were marginal and ranged from 10% to 12%. Multi-drug resistant (MDR) TB was found in 2.8% (6/212) of cases, the highest percentage of MDR TB being found in Alotau (4.6% compared to 2.2% in Madang and 1.8% in Goroka). These results show a significant amount of DR TB being present in all three sites investigated. It is therefore crucial to make diagnosis of DR TB and second-line treatment more widely available in the country to decrease the delay of diagnosing DR TB as well as the duration of possible transmission and to avoid further DR development. Genotyping of Mtb could successfully be conducted of 147 samples. These strains could be classified into three of the so far seven known lineages of Mtb: 75/147 (51.0%) of samples belonged to lineage 4 (European-American lineage), 67/147 (45.6%) to lineage 2 (East-Asian lineage) and 5/147 (3.4%) to lineage 1 (Indo-Oceanic lineage). All three lineages were detected in all three sites, but the individual lineage compositions varied significantly between sites (p