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02:37How 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?
You and your classmates are trying to determine how a disinfectant might kill cells. You observe that when you spill the disinfectant in a tube of reduced litmus milk, the litmus turns blue again. You suggest to your classmates that:
a. The disinfectant might inhibit cell wall synthesis
b. The disinfectant might oxidize molecules
c. The disinfectant might inhibit protein synthesis
d. The disinfectant might denature proteins
e. The disinfectant might damage DNA
How do autoclaving, hot air, and ultra-high-temperature pasteurization illustrate the concept of equivalent treatments?
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.
The use-dilution values for two disinfectants tested under the same conditions are as follows:
Disinfectant A—1:2
Disinfectant B—1:10,000.
If both disinfectants are designed for the same purpose, which would you select?
Use the following information to answer questions 6 and 7. The data were obtained from a use-dilution test comparing four disinfectants against Salmonella Choleraesuis.
G = growth, NG = no growth
Which disinfectant(s) is (are) bactericidal?
a. A,B,C, and D
b. A,C, and D
c. A only
d. B only
e. None of the above
