Use of blood agar along with Lowenstein-Jensen media for rapid isolation of Mycobacterium tuberculosis for early drug susceptibility testing

Abstract

Aims: Tuberculosis diagnosis is still a challenge in resource-limited settings due to poor sensitivity of available tests, long time to reporting and costs. Lowenstein-Jensen (LJ) medium is the most commonly used semisolid medium for culture of Mycobacterium species. However, the growth is very slow which delays the reporting. Hence, there is a need of other better medium for obtaining rapid growth of Mycobacterium species, where advanced automated systems are not available. The aim of the present study was to assess the use of blood agar for primary isolation of Mycobacterium as well as to compare the time required for growth on blood agar and LJ medium. Materials and Methods: All clinical specimens were processed by N-acetyl-L-cysteine-sodium hydroxide decontamination method and inoculated on blood agar slants and LJ medium. These slants were observed daily for any growth. Ziehl-Neelsen stain and auramine phenol stain were used to identify acid-fast bacilli. Time taken for any visible growth on both media were recorded and compared. Results: Totally 94 samples were examined, 13.8% showed acid-fast bacilli in smears. The combined culture positivity with blood agar and LJ media was 12.7%. Mean time to detect macroscopic colonies of Mycobacterium species on blood agar was 20 ΁ 6 days when compared to 30 ΁ 5 days on LJ medium. Conclusion: Blood agar slants can be used as a good supportive media to LJ medium for rapid growth of Mycobacterium species, especially in small laboratories of developing countries where automated systems are not available.