Rapid detection of multidrug-resistant Mycobacterium tuberculosis using the malachite green decolourisation assay

Early detection of drug resistance in Mycobacterium tuberculosis isolates allows for earlier and more effective treatment of patients. The aim of this study was to investigate the performance of the malachite green decolourisation assay (MGDA) in detecting isoniazid (INH) and rifampicin (RIF) resistance in M. tuberculosis clinical isolates. Fifty M. tuberculosis isolates, including 19 multidrug-resistant, eight INH-resistant and 23 INH and RIF-susceptible samples, were tested. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and agreement of the assay for INH were 92.5%, 91.3%, 92.5%, 91.3% and 92%, respectively. Similarly, the sensitivity, specificity, PPV, NPV and agreement of the assay for RIF were 94.7%, 100%, 100%, 96.8% and 98%, respectively. There was a major discrepancy in the tests of two isolates, as they were sensitive to INH by the MGDA test, but resistant by the reference method. There was a minor discrepancy in the tests of two additional isolates, as they were sensitive to INH by the reference method, but resistant by the MGDA test. The drug susceptibility test results were obtained within eight-nine days. In conclusion, the MGDA test is a reliable and accurate method for the rapid detection of INH and RIF resistance compared with the reference method and the MGDA test additionally requires less time to obtain results.

Effect of metanil yellow and malachite green on DNA synthesis in N-nitrosodiethylamine induced preneoplastic rat livers.

Metanil yellow (MY) and malachite green (MG) are textile dyes, which, despite the ban occurs unsrupulously as food colouring agents. Accordingly they constitute a serious public health hazard and are of sufficient environmental concern. We have earlier reported that both MY and MG have tumor enhancing effects on the development of hepatic preneoplastic lesions induced by N-nitrosodiethylamine in rats. In order to understand the possible mechanisms by which MY and MG enhance tumor development, in this study we have tested the effects of MY and MG on DNA synthesis and PCNA expression in preneoplastic hepatic lesions during N-nitrosodiethylamine (DEN) induced hepatocarcinogenesis in male Wistar (WR) rats. Rats were administered 200 ppm DEN through drinking water for a period of one month. Administration of DEN for a period of one month showed an upregulation of cell cycle regulatory proteins namely cyclin D1, CDK4, cyclin E and CDK2. Accordingly, in other experiments, the animals were further administered MY and MG for a period of one month following one month DEN treatment. The effects of MY and MG were monitored on the basis of cell proliferation markers--DNA synthesis and PCNA expression both by immunohistochemical and immunoblotting. Following DEN administration, MY, MG and PB showed stimulation of DNA synthesis and increased PCNA expression when compared with either the corresponding controls or only DEN treated animals. In the present study, enhancing effect of MY, MG and PB on the cell proliferation markers during DEN-induced hepatic preneoplasia in rats was observed.

Antinociceptive effect of purine nucleotides

The antinociceptive effect of purine nucleotides administered systemically (sc) was determined using the formalin and writhing tests in adult male albino mice. The mechanisms underlying nucleotide-induced antinociception were investigated by preinjecting the animals (sc) with specific antagonists for opioid (naloxone, 1 mg/kg), purinergic P1 (caffeine, 5, 10 or 30 mg/kg); theophylline, 10 mg/kg) or purinergic P2 receptors (suramin, 100 mg/kg; Coomassie blue, 30-300 mg/kg; quinidine, 10 mg/kg). Adenosine, adenosine monophosphate (AMP), diphosphate (ADP) and triphosphate (ATP) caused a reduction in the number of writhes and in the time of licking the formalin-injected paw. Naloxone had no effect on adenosine- or adenine nucleotide-induced antinociception. Caffeine (30 mg/kg) and theophylline (10 mg/kg) reversed the antinociceptive action of adenosine and adenine nucleotide derivatives in both tests. P2 antagonists did not reverse adenine nucleotide-induced antinociception. These results suggest that the antinociceptive effect of adenine nucleotides is mediated by adenosine.