Chapter 7 MULTIPLE CHOICE Choose the one alternative that best completes the statement or answers the question Figure 7 1 A suspension of 10 6 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 1 In Figure 7 1 the thermal death point for this culture is A 15 minutes B 170 C C 30 minutes D 50 C E The answer cannot be determined based on the information provided Answer E Figure 7 2 9 Assume 10 E coli cells ml are in a flask 2 Which graph in Figure 7 2 best depicts the effect of placing the culture at 7 C at time x A a B b C c D d Answer D 1 E e 3 Which of the following results in lethal damage to nucleic acids A heat B radiation C certain chemicals D heat and radiation E heat radiation and some chemicals Answer E 4 Which of the following is the best method to sterilize heat labile solutions A autoclave B membrane filtration C freezing D pasteurization E dry heat Answer B 5 Which one of the following is most resistant to chemical biocides A gram positive bacteria B protozoan cysts C viruses with lipid envelopes D gram negative bacteria E mycobacteria Answer D 6 An iodophor is a n A agent that reduces oxygen B phenol C form of formaldehyde D quaternary ammonium compound E iodine mixed with a surfactant Answer E 2 Figure 7 1 6 A suspension of 10 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 7 In Figure 7 1 what is the thermal death time A 60 minutes B 150 C C 120 minutes D 100 C E The answer cannot be determined based on the information provided Answer A 8 All of the following substances are used to preserve foods EXCEPT A calcium propionate B potassium sorbate C biguanides D sodium nitrite E nisin Answer C 9 All of the following factors contribute to hospital acquired infections EXCEPT A gram negative bacteria are often resistant to disinfectants B bacteria may be present in commercial products such as mouthwash C invasive procedures can provide a portal of entry for bacteria D some bacteria metabolize disinfectants E None of the answers is correct all of these factors may contribute to hospital acquired infection Answer E 3 Table 7 3 The following data were obtained by incubating gram positive bacteria in nutrient medium disinfectant for 24 hr then transferring one loopful to nutrient medium subculturing growth no growth 10 In Table 7 3 which disinfectant was most effective against Salmonella A K O B Mortum C Sterl D Doom E The answer cannot be determined based on the information provided Answer E 11 All of the following are methods of food preservation EXCEPT A osmotic pressure B desiccation C high pressure D ionizing radiation E microwaves Answer E 4 Table 7 3 The following data were obtained by incubating gram positive bacteria in nutrient medium disinfectant for 24 hr then transferring one loopful to nutrient medium subculturing growth no growth 12 In Table 7 3 which disinfectant is the most effective at stopping bacterial growth A Doom B K O C Mortum D Sterl E The answer cannot be determined based on the information provided Answer A 13 Application of heat to living cells can result in all of the following EXCEPT A damage to nucleic acids B denaturation of enzymes C breaking of hydrogen bonds D alteration of membrane permeability E decreased thermal death time Answer E 14 Which of the following treatments is the most effective for controlling microbial growth A 63 C for 30 minutes B 72 C for 15 seconds C 140 C for 4 seconds D They are equivalent treatments E None of the answers is correct Answer D 15 Disinfection of water is achieved by all of the following EXCEPT A chlorine B peracetic acid C UV radiation D copper sulfate E ozone Answer B 5 Figure 7 1 6 A suspension of 10 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 16 In Figure 7 1 the decimal reduction time D value for the culture is approximately A 0 minutes B 10 minutes C 30 minutes D 40 minutes E 60 minutes Answer B 17 Which of the following pairs is mismatched A alcohols open wounds B organic acids food preservation C CuSO4 algicide D H2O2 open wounds E Ag wound dressings Answer A 18 If you were preparing nutrient agar at home and did not have an autoclave what could you use to sterilize the nutrient agar A bleach B hydrogen peroxide C boiling for one hour D pressure cooker at 121 C for 15 minutes E oven at 121 C for one hour Answer D 19 Which concentration of ethanol is the most effective bactericide A 100 percent B 70 percent C 50 percent D 40 percent E 30 percent Answer B 20 The preservation of beef jerky from microbial growth relies on which method of microbial control A filtration B ionizing radiation C desiccation D lyophilization E supercritical CO2 Answer C 6 21 Which of the following could be used to sterilize plastic Petri plates in a plastic wrapper A ultraviolet radiation B microwaves C autoclave D sunlight E gamma radiation Answer E 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 Bacteria ml Cider only 2 2 Cider with potassium sorbate 2 0 Sodium benzoate 0 Potassium sorbate sodium benzoate 0 22 In Table 7 2 which preservative is most effective A potassium sorbate C potassium sorbate sodium benzoate B sodium benzoate D no preservative Answer B 23 All of the following substances are effective against nonenveloped viruses EXCEPT A chlorine B ethylene oxide C alcohol D ozone E None of the answers is correct all of these are equally effective against nonenveloped viruses Answer C 7 Table 7 3 The following data were obtained by incubating gram positive bacteria in nutrient medium disinfectant for 24 hr then transferring one loopful to nutrient medium subculturing growth no growth 24 In Table 7 3 which disinfectant was bactericidal A K O B Sterl C Doom D Mortum E The answer cannot be determined based on the information provided Answer D Table 7 1 A disk diffusion test using Staphylococcus gave the following results Disinfectant A B C D Zone of inhibition mm 0 2 5 10 5 25 In Table 7 1 which compound was the most effective against Staphylococcus A A B B C C D D E The answer cannot be determined based on the information provided Answer C 8 Figure 7 2 9 Assume 10 E coli cells ml are in a flask 26 Which graph