**4. Lysis-centrifugation blood culture system**

**3. Culture and drug resistance testing**

144 Tuberculosis - Current Issues in Diagnosis and Management

Significant effort has been invested into further development of simple, alternative pheno‐ typic methods such as the nitrate reductase assay (NRA), thin-layer agar (TLA), colour test (Color Test), the microscopic observation drug susceptibility assay (MODS), the colorimetric redox indicator (CRI) method and phage-based assays, most of which can be set up directly on specimens [6,7,8]. These methods can detect MTB and resistance to INH and RMP. While MODS, NRA and CRI have been endorsed by the WHO, current evidence was considered to

MODS is an extensively validated method that has almost perfect agreement with conven‐ tional DST for INH, RMP and MDR-TB (100%, 97% and 99%). The results are available with‐ in a median of 7 days; the method is cheap, non-commercial and works well on all types of primary specimens as well as on isolates. However, it requires relatively long, detailed staff

TLA recently demonstrated a good performance of the MDR-/XDR-TB colour test for the identification of MTB complex and detection of resistance to INH, RMP and ciprofloxacin in

Molecular techniques are aimed at the nucleic acid of the mycobacterium as the analyte. Ri‐ bosomal rRNA is useful genetic target for the identification of organisms, since it often con‐ tains spesific sequences and is present in the cells and media in high quantity due to the growth of the mycobacteria. There are various applications of molecular tecniques for the

PCR is the common format of nucleic acid amplification tests (NAAT); other methodologies include ligase chain reaction, strain displacement amplification, loop-mediated isothermal amplifi cation (LAMP) and transcription mediated amplification. More recently, real-time (RT) PCR technologies based on fluorescent- probe detection or melting-curve analysis have

These molecular techniques also aimed detecting resistance genes. Example includes; DNA probe and DNA sequencing of MTB gene such as catalase (katG) or RNA polymerase (rpoB). Mutations in these genes have been associated with resistance to isoniazid and ri‐ fampicin respectively. The using of molecular primers in real- time PCR reaction can differ‐ entiate between the presence of the wild- type sequence and mutated sequence associated with drug resistance. Molecular tests are rapid (within few hours), highly sensitive and spe‐ cific, but expensive, requires expertise and may not differentiate active infection as DNA from a dead organism during antibiotic treatment can be detected and amplified by PCR [17]. Genotypic methods are not routinely used in the mycobacterium laboratory; they are

be insufficient for recommending the use of TLA or phage-based assays [8].

**3.1. Phenotypic methods**

training. [6,7,9,10]

**3.2. Genotypic methods**

been developed [12-16].

detection and identification of MTB.

essentially for research purposes [18,19].

cultures [11].

The recovery of mycobacterium from peripheral blood and bone marrow samples may be improved by lyses- centrifugation blood culture method. In this method, blood is put into a tube containing an anticoagulant and an agent to effect rupture of both erythrocytes and neutrophils. Following centrifugation of the tube, the sediment is inoculated into the appro‐ priate culture media. This method has increased both the yield and shortened the time of recovery of mycobacteria from blood cultures [21].
