The effect of freezing and storage at -60 degrees C on the viability of Mycobacterium leprae

Suspensions of M. leprae in 10% glycerol and 0.1% bovine serum albumin were quick-frozen and stored for various periods of time at −60 °C. Viability of the bacterial suspensions, measured by means of Shepard's mouse footpad technique, did not decrease progressively during prolonged storage, suggesting that the observed decreases in viability resulted from the freezing process rather than from storage. Considerable variability was noted in the loss of viability which resulted from freezing.