Detection of rifampin resistance in Mycobacterium tuberculosis by double gradient-denaturing gradient gel electrophoresis.

We applied double gradient-denaturing gradient gel electrophoresis (DG-DGGE) for the rapid detection of rifampin (RMP) resistance from rpoB PCR products of Mycobacterium tuberculosis isolates and clinical samples. The results of this method were fully concordant with those of DNA sequencing and susceptibility testing analyses. DG-DGGE is a valid alternative to the other methods of detecting mutations for predicting RMP resistance.

Study on mutations and antiretroviral therapy (SMART): preliminary results.

Resistance to antiretroviral drugs is believed to be an important cause of treatment failure in human immunodeficiency virus (HIV)-infected patients, however, the role of susceptibility assays in the management of these individuals needs to be defined. SMART (study on mutations and antiretroviral therapy) is an ongoing study on mutations and antiretroviral therapy focused particularly on HIV-infected patients treated with two nucleoside analogue reverse transcriptase inhibitors (NRTIs). Plasma HIV-1 RNA was assessed by NASBA (nucleic acid sequence-based amplifications) (Organon Teknika, Boxtel, The Netherlands) with a detection limit of 80 copies/ml, whereas resistance was assessed by direct sequencing of the RT pol gene in patients with detectable viraemia, and by Antivirogram (Virco) in non-responder patients. The preliminary results of this study show that both genotypic and phenotypic assays identify mutated viral strains in the majority of patients failing a dual regimen. Furthermore, the data indicate a high rate of genotypic resistance to lamivudine in both responders and non-responders, a high rate of phenotypic resistance to lamivudine in non-responders, no genotypic resistance to didanosine and stavudine in responders, and a very low rate of both genotypic and phenotypic resistance to didanosine and stavudine in non-responders.