Sample decontamination
Sputum samples were decontaminated through sodium hydroxide-N-acetyl-Lcystein (NaOH-NALC) method. For this purpose, sputum samples (5-10 ml) were taken into a follicle tube, an equal volume of NaOH and sodium citrate solution was added. After vortexes for 15-30 seconds samples were kept at 20-25°C for 15 minutes for decontamination. The tube was filled 2 cm from top with phosphate buffer. Vortexes and Centrifuge at 3000 xg for 15-20 minutes. Supernatant was discarded and 2-2.5ml Phosphate buffer (pH6.8) was added [13].