Among isolates with complete patterns, 72/162 (44.4%) were clustered. Despite potential fitness costs associated with resistance-conferring mutations [25], the proportion of clustered

Tariquidar datasheet strains was not significantly different among drug-sensitive (60/137, 43.8%) and drug-resistant (12/25, 48.0%) isolates of M. tuberculosis. To distinguish between primary resistance and acquired resistance, clustered isolates sharing identical drug resistance-conferring mutations were considered. Five of the 12 (41.7%) drug-resistant isolates involved in molecular clusters shared their drug resistance-conferring mutations with other isolates in the same cluster, thus strongly suggesting patient-to-patient transmission. Conclusions This study provides so far missing data about drug resistance-conferring mutations in M. tuberculosis isolates

from Madang in PNG. Monitoring drug resistance is essential to prevent the spread of resistant bacteria, especially in diseases requiring lengthy treatments such as TB. Our data suggests that not all present Akt activator drug resistance associated mutations may be detected by molecular tests, which mainly focus on a subset of polymorphisms only. However, given the complex implementation of culture-based DST in resource-constrained settings, PNG may be well suited for an accelerated roll-out of molecular drug resistance testing in order to better tackle the emergence and the transmission of drug-resistant M. tuberculosis strains. Methods Study site and patient characteristics In 2005-2007, a pilot study was conducted in Madang (PNG) at the Modillion Hospital, which is the main point of care in Madang province. In April 2009, a cohort study was initiated in the same hospital and two smaller health centers in close vicinity to Madang town. Patients above 14 years were included if having microscopically confirmed pulmonary TB or other clinical evidence suggesting smear-negative TB. Treatment and

follow-up were planed according to the directly observed treatment, short-course (DOTS) program. Demographic and clinical data were available for all Fossariinae patients, except those recruited during the 2005-2007 pilot study. Sample processing Sputum samples were examined by light microscopy after Ziehl-Neelsen staining. Decontamination was conducted according to Petroff’s method [26]. DST was performed by proportion method [27] at the Queensland Mycobacterial Reference Laboratory in Australia using BACTEC™ MGIT™ 960 (Beckton Dickinson, USA) and the following drug concentrations: RIF (1.0 μg/mL), INH (0.1 and 0.4 μg/mL), Ethambutol (5.0 μg/mL), Pyrazinamide (100 μg/mL), Streptomycin (1.0 μg/mL), Amikacin (1.0 μg/mL), Kanamycin (5.0 μg/mL), Ofloxacin (2.0 μg/mL), Capreomycin (2.5 μg/mL), ETH (5.0 μg/mL), p-Aminosalicylic acid (4.0 μg/mL), and Cycloserine (50.0 μg/mL).