Identificazione molecolare di mutazioni conferenti resistenza a rifampicina ed isoniazide in M. tuberculosis in campioni clinici diretti mediante Genotype MTBDR (Hain Lifescience)

The widespread of multi-drug resistant (MDR) Mycobacterium tuberculosis, resistant at least to rifampin (RIF) and isoniazid (INH), represents serious threats to the control of tuberculosis (TB) and increases the public health challenge worldwide. Surveillance program and rapid identification of drug-resistance strains are key-elements for an early and appropriate TB management. The aim is to evaluate the Genotype MTBDR (Hain Lifescience, Nehren, Germany), a reverse hybridization-based assay, as a rapid tool to identify mutations in the rpoB and katG genes associated to RIF-/INH-resistance directly in clinical specimens.We also evaluate the performance of a paper based device (Genocard – Hain Lifescience, Nehren, Germany) to collect and transport inactivated biological material. The test was evaluated retrospectively on 68 respiratory samples with positive cultures for M. tuberculosis. Considering the smear-positive samples only, the Genotype MTBDR gave interpretable results in 56 out of 57 samples (98.2%). The main limitations of the Genotype MTBDR are the difficulties in the amplification from smear-negative samples and the low sensitivity for the INH-resistance. The inclusion of probes targeting other regions involved in INH-resistance will increase the sensitivity of the test. The GenoCard, with its easy- and rapid-to use features, represents a functional tool for the sample collection with cost-effective and bio-safety benefits.The possibility to use the GenoCard directly in amplification reactions facilitates the gathering of data by molecular approaches.