Section 1
Review
The thermal death time for a suspension of Bacillus subtilis endospores is 30 minutes in dry heat and less than 10 minutes in an autoclave. Which type of heat is more effective? Why?
If pasteurization does not achieve sterilization, why is pasteurization used to treat food?
Thermal death point is not considered an accurate measure of the effectiveness of heat sterilization. List three factors that can alter thermal death point.
The antimicrobial effect of gamma radiation is due to (a)_______ The antimicrobial effect of ultraviolet radiation is due to (b)_______
A bacterial culture was in log phase in the following figure. At time $x$, an antibacterial compound was added to the culture. Draw the lines indicating addition of a bactericidal compound and a bacteriostatic compound. Explain why the viable count does not immediately drop to zero at $x$.GRAPH CAN'T COPY.
How do autoclaving, hot air, and pasteurization illustrate the concept of equivalent treatments?
How do salts and sugars preserve foods? Why are these considered physical rather than chemical methods of microbial control? Name one food that is preserved with sugar and one preserved with salt. How do you account for the occasional growth of Penicillium mold in jelly, which is $50 \%$ sucrose?
The use-dilution values for two disinfectants tested under the same conditions are as follows: Disinfectant A-1:2; Disinfectant $\mathrm{B}-1: 10,000$. If both disinfectants are designed for the same purpose, which would you select?
A large hospital washes burn patients in a stainless steel tub. After each patient, the tub is cleaned with a quat. It was noticed that 14 of 20 burn patients acquired Pseudomonas infections after being bathed. Provide an explanation for this high rate of infection.
What bacterium has porins, is resistant to triclosan, and survives and may grow in quats?