Exam 7: The Control of Microbial Growth

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 at 7°C at time x?

Figure 7.2 A suspension of 106 Bacillus cereus endospores was put in a hot- air oven at 170°C. Plate counts were used to determine the number of endospores surviving at the time intervals shown. -In Figure 7.2, the thermal death time for this culture is

Place the following surfactants in order from the most effective to the least effective antimicrobial a 1- Soap; 2- Anionic detergent; 3- Cationic detergent.

Table 7.2 The fate of E. coli O157:H7 in apple cider held at 8°C for 2 weeks, with and without preservatives, is shown below: Cider only 2.2 Cider with potassium sorbate 2.0 Sodium benzoate 0 Sorbate + benzoate 0 -In Table 7.2, which preservative is most effective?

Which concentration of ethyl alcohol is the most effective bactericide?

Which of the following affects the elimination of bacteria from an object?

Which of the following is a limitation of the autoclave?

Which one of the following does not belong with the others?

Phenolics differ from phenol in that phenolics are all of the following except

Figure 7.2 A suspension of 106 Bacillus cereus endospores was put in a hot- air oven at 170°C. Plate counts were used to determine the number of endospores surviving at the time intervals shown. -In Figure 7.2, the thermal death point for this culture is

Which one of the following is most resistant to chemical biocides?

Which of the following is not a heavy metal?

All of the following contribute to hospital- acquired infections except

Figure 7.1 -Assume that one culture is a freshly opened package of dried yeast with 0.1% moisture, another culture is the same yeast with 7.5% moisture, and the third culture is a package of yeast mixed with water. Each culture was exposed to 130°C in a hot- air oven. Which graph in Figure 7.1 most likely shows the yeast with 0.1% moisture?

Which of the following is used for surgical hand scrubs?

Table 7.1 A disk- diffusion test using Staphylococcus gave the following results: A 0 B 2.5 C 10 D 5 -In Table 7.1, which compound was bactericidal?

Which of the following is not used for the disinfection of water?

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.) $\quad\quad\quad\quad\quad\quad\quad\quad \underline{\text { Doom }} \quad \quad\quad\quad\quad\quad\quad\underline{K O}$ Dilution Initial Subculture Initial Subculture 1:16 - + + + 1:32 - + + + 1:64 - + + + 1:128 + + + + $\quad\quad\quad\quad\quad\quad\quad\quad \underline{\text { Mortum } }\quad\quad\quad\quad\quad\quad \underline{\text { Sterl }}$ Dilution Initial Subculture Initial Subculture 1:16 - - - + 1:32 - + + + 1:64 + + + + 1:128 + + + + -In Table 7.3, which disinfectant is the most effective at stopping bacterial growth?

The antimicrobial activity of chlorine is due to which of the following?

Which of the following treatments does not yield a sterile product?