10. Dynamics of Microbial Growth

The temperature of a human body is anywhere from 35-40C. What type of pathogen can infect humans?

By deep-freezing, bacteria can be stored without harm for extended periods. Why do refrigeration and freezing preserve foods?

Which of the following is true about the optimum growth temperature of most mesophiles?

a) They can grow well at 37^0C.

b) They are more likely to grow at refrigerator temperatures.

c) They can strive well in extremely high temperatures.

d) All of the above.

Which one of the following temperatures would most likely kill a mesophile?

a. -50℃

b. 0℃

c. 9℃

d. 37℃

e. 60℃

The thermal death time for a suspension of Bacillus subtilis endospores is in dry heat and less than 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.

Label each statement that follows as true or false, and correct the false statements so they are true:

a. Most pathogens would be considered mesophilic alkaliphiles.

b. Sterilization is a form of decontamination.

c. Disinfection is a form of decontamination.

d. High-level germicides achieve sterilization.

e. Ionizing radiation is a form of chemical microbial control.

f. Standard pasteurization is a way to sterilize milk.

You have a patient who is suffering from a Clostridioides difficile infection. Which of the following would most likely be recommended to decontaminate small heat-stable equipment used for the patient?

a. Autoclave all equipment at 121°C for 15 minutes.

b. Boil equipment for 3 minutes.

c. Place the equipment in a hot-air oven at 121°C for 15 minutes.

d. Treat all equipment with a detergent solution.

e. None of the above.

The _____________ is the time needed to kill 90 percent of a given microbial population at a set temperature. The _____________ is the lowest temperature needed to kill all microbes in a sample within 10 minutes.

Organisms that preferentially may thrive in icy waters are described as:

a. Barophiles

b. Thermophiles

c. Mesophiles

d. Psychrophiles

The lowest temperature at which a microbe continues to metabolize is called its ___________ .

High temperature affects the shape of particular molecules. How does this affect the life of a microbe?

Why are Gram-negative bacteria more susceptible to heat than Gram-positive bacteria?

Calculate the decimal reduction time (D) for the two temperatures in the following graph.