A comparative study of special agar medium (Redmond) and simple agar medium for the phage-typing of mycobacteria.

Phage-typing is an important technique for classifying mycobacteria and optimum conditions for growth are required to bring the organisms into the logarithmic phase of growth needed for their exposure to phages. The quality of the media used for growing the strains selected for typing is therefore important.Comparative trials on the propagation of 3 different mycobacterial phages (MyF(1)-P/58; MyF(2)-P/59, both isolated in Prague, and GS4E, supplied by W. B. Redmond, Atlanta, Ga., USA) on ATCC 607 and S(1)P (scotochromogen) mycobacterial strains grown on RVA (Redmond) medium and on simple N-1 agar, with and without albumin, were undertaken. The results showed that the Redmond medium is very sensitive for growing atypical strains but not for multiplying phages. The lytic plaques were less developed on this medium and the metabolic activity of the phages-as shown by the absence of a positive tellurite phenomenon-was impaired. Further comparative trials with slowly growing mycobacteria are in progress.