Preservation of mycobacteria at -70 degrees C: survival of unfrozen suspensions in transit

Mycobacteria stored at -70 degrees C retain 100% viability and maintain their definitive taxonomic, serologic, immunologic, and pathogenic properties. When shipped at ambient temperatures, however, suspensions of all mycobacteria lose viability in transit, with those species having a narrow temperature range for growth (Mycobacterium tuberculosis and M. bovis) being most severely affected. In spite of these losses, all strains retain their definitive taxonomic properties. If care is taken in pre-testing and post-testing the microbial populations being preserved, mycobacteria are probably best shipped in the lyophilized state, and this procedure has been successfully used for several international studies.