Comparison of two different dectontamination procedures applied before the mycobacterium tuberculosis isolation

The aim of this study is to compare the homogenization and decontamination efficiency of two methods, namely n-acetyl-l-cysteine-sodium hydroxide (nalc-naoh) decontamination method and decomics decontamination kit, in sputum samples spiked with Mycobacterium tuberculosis H37 Ra, by using staining, culture and pcr methods. Two series of spiked bacterial suspensions were prepared from M. tuberculosis H37Ra strain. Serial dilutions were made in three ml sputum containing sterile tubes, by adding 0.5 ml bacteria to the concentrations of 10¹/ml-10⁸/ml. One of the series was used for decontamination with NALC-NaOH method and the other for Decomics decontamination kit. The study was carried out 37 times. After decontamination, samples were stained; inoculated in Löwenstein Jensen (LJ) medium and Middlebrook (MB) 7H10 medium and PCR was performed. There was no significant difference between the results of the NALC-NaOH method and Decomics method in acid-fast bacilli (AFB) staining and PCR examinations at 10⁸, 10⁷, 10⁶, 10³, 10² and 10¹/ml. However, in the rest of the concentrations, significant differences were found between the NALC-NaOH method and the Decomics method. (AFB staining (10⁵/ml) p=0.016 and PCR (10⁵/ml) p=0.5, AFB staining (10⁴/ml) p=0.012 and PCR (10⁴/ml) p=0.016). There was no significant difference between the results of NALC-NaOH method and Decomics method at 10⁸, 10⁷, 10⁶, 10⁵,10³, 10² and 10¹/ml in cultures on MB and LJ media. However, a significant difference was found between the NALC-NaOH method and the Decomics method in cultures with 10⁴/ml bacteria. As a result, it can be said that, Decomics efficiently decontaminates sputum and bacilli can be detected in the concentrations of approximately 105-108/ml. Usage of Decomics decontamination kit can be helpful where tuberculosis is endemic and in areas where the laboratory facilities are inadequate since Decomics kit does not require centrifugation. Keywords: Mycobacterium tuberculosis complex, homogenization decontamination, isolation