Preservation of mycobacteria st -70 degrees C: persistence of key differential features

The advantages of long-term preservation of suspensions of mycobacteria by storage at -70 degrees C established in earlier studies are reinforced by present evidence that freezer storage does not alter key taxonomic features used to identify mycobacteria. Occasional discrepancies in biochemical test characteristics of mycobacteria that have been stored in the freezer and reconstituted at 37 degrees C reflect only sluggish metabolic activity, which is restored to normal on repeat testing.