EVALUATION OF DEFINED MEDIA SUITABLE FOR ISOLATION OF AUXOTROPHIC MUTANTS OF MYCOBACTERIA

In order to investigate the production of auxotrophs of slow growing m ycobacterial pathogens, an evaluation of defined liquid and solid medi a suitable for Mycobacterium tuberculosis, Mycobacterium bovis and Myc obacterium paratuberculosis was undertaken. Five defined liquid media were evaluated. A number of solid support matrices was added to the li quid media to produce solid media for evaluation. Tween 80 was added t o all media to produce diffuse homogeneous growth. Although satisfacto ry growth in defined liquid media was achieved with all strains tested , poor growth was generally observed in the equivalent defined solid m edium for strains belonging to the tuberculosis complex. Only M. parat uberculosis produced satisfactory growth on defined solid media, espec ially on Middlebrook 7H9. The inhibitory effect of Tween 80 and the pr esence of inhibitory factor(s) in agar were confirmed. Partial removal or inactivation of these factors by the addition of absorbents to the media was achieved.