Only 21% were known human immunodeficiency virus (HIV) status. Among these, 52% were HIV-positive. PZA susceptibility testing Pyrazinamide susceptibility testing was performed using the BACTEC MGIT 960 PZA system (Becton Dickinson) as recommended by the manufacturer. The medium used was modified Middlebrook 7H9 broth (pH 5.9)
containing 100 μg/ml PZA. Mycobacterium bovis BCG ATCC 34540 and Mycobacterium tuberculosis H37Rv ATCC 27294 were used as pyrazinamide resistant and susceptible controls, respectively. 8-Bromo-cAMP The control strains were included in all test sets. Pyrazinamidase assay Pyrazinamidase activity was determined by Wayne’s check details method . This method is based on the detection of POA, which forms a compound with ferrous ammonium sulphate
to produce a brownish or pink colour. Briefly, a heavy loopful BAY 63-2521 datasheet of M. tuberculosis colonies was obtained from cultures that were actively growing in LJ medium and inoculated onto the surfaces of two agar butt tubes, each containing 5 ml of Wayne’s medium supplemented with 100 μg/ml of PZA (Sigma-Aldrich, USA). The tubes were incubated at 37°C. Four days after incubation, 1 ml of freshly prepared 1% ferrous ammonium sulphate was added to the first tube. The tube was left at room temperature for 30 minutes and examined. The assay was positive if a pink or brownish band was present on the surface of the agar. If the test was negative, the test was repeated with a second tube and examined after 7 days of incubation. The results were blindly read by two independent observers. M. bovis BCG and M. tuberculosis H37Rv
were used as negative and positive controls, respectively. DNA extraction Mycobacterial DNAs were extracted by the boiling method . Briefly, one loopful of M. tuberculosis colonies obtained from LJ medium was suspended in 200 μl of TE buffer (10 mM Tris-HCl, 1 mM EDTA, pH 8.0) and boiled for 20 minutes. The supernatant was collected by centrifugation at 12,000 rpm for 5 min and used as the DNA template for amplification. Amplification and sequencing of the amplified pncA gene The pncA forward primer, pncAF1, (5′-GCGGCGTCATGGACCCTATATC-3′) was located 82 bp Dichloromethane dehalogenase upstream of the start codon, and the reverse primer, pncAR1, (5′-CTTGCGGCGAGCG CTCCA -3′) was located 54 bp downstream of the stop codon of M. tuberculosis pncA (Rv2043c). The expected size of the PCR products was 696 bp. PCR was performed in a total volume of 50 μl, and the PCR reaction mixture consisted of 0.25 mM dNTP (Fermentas, CA, USA), 10 mM Tris-HCl (pH 8.3), 50 mM KCl, 2.0 mM MgCl2, 20 pmol of each primer, 1 unit of Taq DNA polymerase (Fermentas, CA, USA) and 5 μl of crude DNA. The PCR reactions were performed under the following conditions: initial denaturation at 94°C for 5 min; 40 cycles of denaturation at 94°C for 1 min, annealing at 62°C for 1 min and extension at 72°C for 1 min; and 1 final cycle of extension at 72°C for 10 min.