The Heat Inactivation of Antistaphylococcus Bacteriophage

Early work on bacteriophage included several studies of the effect of heat on the lytic principle. For example, d'Herelle (1) found Shiga bacteriophage survived exposure to 65°C. for 1⁄2 hour. Kabeshima (2) working with the same phage observed activity after 1⁄2 hour at 70°C. and set the inactivation temperature at 75°C. , using a like period of exposure. Others, particularly Weinberg and Aznar (3) and Tchang Kouo Ngen and Wagemans (4) reported that 80°C. was required for complete destruction of phage. Bumet and McKie (5) diluted phage suspensions with salts of sodium, potassium, and ammonium and found that such preparations were very easily inactivated by moderate heat (60°C.). Small amounts of calcium, magnesium or barium inhibited this effect, d'Herelle (6) summarizes his experience as follows: " . . . . I have never yet found a bacteriophage, even of maximum virulence, which was not rendered totally avimlent (or destroyed?) at a temperature in the neighborhood of 75°C. nor have I found one which was rendered avirulent at temperatures below 65°C. '' The concept of rate of inactivation as an important factor contributing to the experimental results appears to have been neglected except for contributions by Tomaselli (7) and Nanavutty (8). Tomaselli exposed a Shiga lysate to various temperatures and estimated the active fraction surviving after 10, 20, and 30 minutes. His data are unique in indicating that the degree of inactivation at any temperature is a function of temperature alone, being quite independent of the period of exposure. Nanavutty (8) plotted "survivor" curves for Shiga lysates suspended in various menstrua and exposed to different temperatures. He found the curves of logarithms of surviving phage particles plotted against time to be constantly concave, 363