Exploitation of Culture Medium forMycobacterium tuberculosis

Abstract

The culture media for Mycobacterium tuberculosis (MTB) were contrived from both egg-based and agar based ingredients. In 1903, Dorset introduced the first egg-based medium. It was followed by the invention of Lowenstein-Jensen and Ogawa media that contain whole eggs as nutrient and malachite green to inhibit the growth of contaminants. These media have been used worldwide for their usefulness and inexpensiveness. However they have a fundamental disadvantage that the cultivation time for mycobacterial growth takes more than 4 weeks. In 1947, Dubos introduced the first agar medium and followed by the invention of the 7H10 by Middlebrook and Cohn. A powder base of these media contains agar, combination of seven salts, L-glutamic acid, pyridoxine, biotin, and malachite green. This requires the addition of the oleic acid, albumin, dextrose, and catalase (OADC) growth supplement. BACTEC MGIT960 has recently been introduced for rapid cultivation of MTB, which is fully automated liquid culture system with modified 7H9 broth. Agar-based medium developed by Middlebrook has a number of advantages over egg-based medium. One of them is transparency, which enables earlier detection of growing colonies. The major disadvantages of agar media are the high cost of OADC and the need for a CO 2 incubator. In conclusion, there is a need for a new agar medium, which can be produced at a lower cost and earlier growth detection. In this review, we introduced the growth promoting factors which can be used as an alternative new growth supplement, cAMP and resuscitation-promoting factor (Rpf). These factors may abrogate a lag in adaption of the bacilli in culture media.