WHO cooperative studies on the phage-typing of mycobacteria. 1. Phage lysis of Czechoslovak and Italian strains of Mycobacterium tuberculosis.

Although phage-typing of some pathogenic microbes-e.g., Escherichia coli and the genera Salmonella, Staphylococcus, and Streptomyces-is in routine use, little progress has yet been made in the phage-typing of mycobacteria, chiefly because mycobacteriophages possess a polyvalence that prevents the reliable identification of individual species of mycobacterium. Furthermore, laboratories cannot compare their results because they employ different methods and culture media and also because the phages used cannot be accurately identified. It has been shown that internationally reproducible results can be obtained for M. tuberculosis by selecting suitable mycobacteriophages and sensitive culture media, and by using a standardized technique of phage-typing. Under these conditions, phage lysis may be utilized to classify strains of M. tuberculosis.

Media and methods for phage-typing mycobacteria.

Media widely used for primary isolation, for drug-sensitivity tests and for type differentiation of mycobacteria have been tested for use in phage studies on the tubercle bacilli. Modifications of each of these media provided some improvement in phage activity on some strains of mycobacteria but not on others. During these studies it was observed that certain substances augmented phage activity, while other substances were found to have the opposite effect. On the basis of these results, a new medium has been formulated. This medium can be used without agar as a liquid medium for growth of the mycobacteria or with agar as a solid medium for isolated plaques and routine test dilution (RTD) spots. An outline of a pilot phage-typing test on three species of Mycobacterium is included.