The effect of changes in nutritional components and environmental factors on growth pattern and biofilm formation by Mycobacterium marinum CCUG 20998

Mycobacterium marinum is a slow growing nontuberculosis mycobacterium. This organism can cause disseminated granulomatous infections in fish, called ‘fish tuberculosis’. Changes in nutritional components in culture medium and environmental conditions may lead to some changes in growth patterns and biofilm formation having new characteristics. The aim of this study was the evaluation of changes in medium components and environmental factors on the growth pattern and biofilm formation of M. marinum CCUG 20998. M. marinum CCUG 20998 was grown in 7H9 broth medium containing different concentrations of Tween 80 (0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 % v/v), Oleic Albumin Dextrose Catalase supplement (OADC), (4, 8, 12, and 16 % v/v) and glycerol (30, 35, 40, 45, and 50 % v/v). The changes in growth patterns and biofilm formation were determined by using measurement of optical density and staining by crystal violet. The obtained results showed that maximum growth was at 0.4 % of Tween 80. Oleic Albumin Dextrose Catalase supplement at different concentrations did not show any significant effect on the growth pattern. Decreasing the glycerol concentration significantly decreased the growth rate. The maximum biofilm formation was obtained in 35 % glycerol without Tween 80 and OADC in culture medium. Discussion and According to the obtained results, Tween 80 and glycerol in the formulation of Middlebrook 7H9 Broth are very critical for M. marinum CCUG 20998 growth. In contrast, Oleic Albumin Dextrose Catalase supplement can be omitted from the medium formulation due to showing no significant effect on the growth pattern.