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Exam 7: The Control of Microbial Growth

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Question 21

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Which of the following best describes the pattern of microbial death?

A) The pattern varies depending on the species.
B) The pattern varies depending on the antimicrobial agent.
C) The cells in a population die at a constant rate.
D) All of the cells in a culture are never killed.
E) All the cells in a culture die at once.

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Question 22

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Which of the following substances is the least effective antimicrobial agent?

A) Cationic detergents
B) Phenolics
C) Iodine
D) Soap
E) Alcohol

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Question 23

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Table 7.3 The following data were obtained by incubating the bacteria in nutrient medium + disinfectant for 24 hr, then transferring one loopful to nutrient medium (subculturing.) $\quad\quad\quad\quad\quad\quad\quad\quad \underline{\text { Doom} } \quad \quad\quad\quad\quad\quad\quad\underline{K O}$ $\begin{array}{rrrrr}\text { Dilution } & \text { Initial } & \text { Subculture } & \text { Initial } & \text { Subculture } \\1: 16 & - & + & + & + \\1: 32 & - & + & + & + \\1: 64 & - & + & + & + \\1: 128 & + & + & + & +\end{array}$ $\quad\quad\quad\quad\quad\quad\quad\quad \underline{\text { Mortum }} \quad\quad\quad\quad\quad\quad \underline{\text { Sterl }}$ $\begin{array}{rrrrrr}\text { Dilution } & \text { Initial } & \text { Subculture } & \text { Initial } & \text { Subculture } \\1: 16 & - & - & - & + \\1: 32 & - & + & + & + \\1: 64 & + & + & + & + \\1: 128 & + & + & + & +\end{array}$ -In Table 7.3, which disinfectant was bactericidal?

Which of the following treatments is the most effective for controlling microbial growth?

Which of the following pairs is not correctly matched?

Which of the following could be used to sterilize plastic Petri plates in a plastic wrapper?

Figure 7.3 Assume 109 E. coli cells/ml are in a flask. -Which graph in Figure 7.3 best depicts the effect of placing the culture in an autoclave for 15 min. at time x?

Which of the following does not achieve sterilization?

Bacterial death will result from damage to which of the following structures?

Table 7.1 A disk- diffusion test using Staphylococcus gave the following results: $\begin{array}{cc} \underline{\text { Disinfectant }}& \underline{\text { Zone of inhibition (mm) }}\\\text { A } & 0 \\\text { B } & 2.5 \\\text { C } & 10 \\\text { D } & 5\end{array}$ -In Table 7.1, which compound was the most effective against E. coli?

Figure 7.1 -In Figure 7.1, what is the thermal death time for culture a?

Glutaraldehyde is considered one of the most effective disinfectants for hospital use. Which of the following would not be true about glutaraldehyde?

Which of these is not an oxidizing agent?

Which of the following substances can sterilize?

Which of the following is not a direct result of heat?

Foods are preserved with all of the following except

Which one of the following is most useful for disinfecting medical instruments?

Which of the following is best to sterilize heat- labile solutions?

Which of the following is not effective against nonenveloped viruses?

Iodophors differ from iodine (I2) in that iodophors