Chapter 7: The Control of Microbial Growth*

The minimum sterilizing conditions in a steam autoclave are A) 121o C at 15 psi for 15 minutes. B) 63o C for 30 minutes. C) 160o C for 2 hours. D) 71.6o C for 15 seconds. E) 100o C for 30 minutes.

A) 121o C at 15 psi for 15 minutes.

In Table 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.

A) Doom

Which of the following best describes the pattern (or rate) of microbial (bacterial) death? A) The cells in a population die at a constant rate. B) All the cells in a culture die at once. C) Not all of the cells in a culture are killed. D) The pattern varies depending on the antimicrobial agent. E) The pattern varies depending on the species.

A) The cells in a population die at a constant rate.

Which of the following pairs of terms is mismatched? A) bacteriostatic — kills vegetative bacterial cells B) germicide ‐ kills microbes C) virucide ‐ inactivates viruses D) sterilant — destroys all living microorganisms E) fungicide — kills yeasts and molds

A) bacteriostatic — kills vegetative bacterial cells

Some microbial control agents are able to _____ cell proteins by breaking bonds that maintain the native state (three‐dimensional configuration) of the proteins. A) denature B) bind C) dissolve D) activate E) All of the choices are correct.

A) denature

An agent used to reduce the number of bacteria on a toilet seat would most accurately be called a(n) A) disinfectant. B) antiseptic. C) aseptic. D) fungicide. E) virucide.

A) disinfectant.

Disinfection of beverages such as apple juice, milk and wine is optimally achieved by A) pasteurization. B) chlorination. C) moist heat autoclave. D) filtration. E) boiling water.

A) pasteurization.

The lowest temperature needed to kill all microbes in 10 minutes is the A) thermal death point (TDP). B) thermal death time (TDT). C) sporicidal time. D) death phase point. E) None of the choices is correct

A) thermal death point (TDP).

Which control method would not be a suitable choice for killing Mycobacterium in a capped culture tube? A) ultraviolet (germicidal) light B) gamma rays C) 121o C at 15 psi for 15 minutes D) 200o C for 2 hours E) All of the choices are correct.

A) ultraviolet (germicidal) light

In Figure 1, what is the thermal death of B. cereus? A) 150°C B) 60 minutes C) 120 minutes D) 100°C E) The answer cannot be determined based on the information provided.

B) 60 minutes

Which concentration of ethanol is the most effective usable bactericide? A) 100 percent B) 70 percent C) 50 percent D) 40 percent E) 30 percent

B) 70 percent

_____ radiation excites atoms to a higher energy state within molecules such as DNA that then leads to the formation of pyrimidine dimers. A) Infrared B) Ultraviolet C) Gamma D) Particle E) Ionizing

B) Ultraviolet

Which graph in Figure 2 best depicts the effect of placing the E. coli culture in an autoclave for 15 minutes at time x? A) a B) b C) c D) d E) e

B) b

Placing organisms at 4o C is A) bacteriocidal. B) bacteriostatic. C) decontamination. D) sterilization. E) None of the choices is correct.

B) bacteriostatic.

The compound that is an organic base containing chlorine and two phenolic rings, and is used increasingly for wound degerming, neonatal washes, hand scrubbing, and prepping surgical skin sites is A) carbolic acid. B) chlorhexidine. C) triclosan. D) formalin. E) quarternary ammonium compounds.

B) chlorhexidine.

The method of removing vegetative microbial life forms from inanimate objects is termed A) antisepsis. B) disinfection. C) sterilization. D) decontamination. E) degerming.

B) disinfection.

Which of the following methods will not achieve sterilization? A) dry heat B) pasteurization C) autoclave D) moist heat E) ethylene oxide

B) pasteurization

What does Pasteurization do to microbes? A) kills all vegetative forms. B) reduces the number of vegetative forms. C) reduces the number of endospores. D) increases food nutrient value. E) None of the choices is correct.

B) reduces the number of vegetative forms. ???????????

Data showing the fate of E. coli O157:H7 in apple cider held at 8°C for 2 weeks, with and without preservatives: Bacteria/ml Cider only 2.2 Cider with potassium sorbate 2.0 Cider with Sodium benzoate 0 Cider with Potassium sorbate + sodium benzoate 0

B) sodium benzoate

The process that destroys or removes all microorganisms and microbial forms including bacterial endospores on inanimate objects is A) disinfection. B) sterilization. C) antisepsis. D) sanitization. E.) degermation.

B) sterilization.

The shortest time required to kill all the microbes in a sample at a specified temperature is called the A) thermal death point (TDP). B) thermal death time (TDT). C) sporicidal time. D) death phase point. E) None of the choices is correct.

B) thermal death time (TDT).

The easiest microbial forms to kill or inhibit are A) naked viruses. B) vegetative bacteria and fungi. C) endospores. D) protozoan cysts. E) mycobacteria and staphylococci.

B) vegetative bacteria and fungi

A disk‐diffusion test for disinfectants using Staphylococcus aureus gave the following results: Disinfectant Zone of inhibition around disk (mm) A 0 B 2.5 C 10 D 5 In Table 1, which compound was the most effective against S. aureus? A) A B) B C) C D) D E) The answer cannot be determined based on the information provided.

C) C

Which is correct regarding the rate of microbial death? A) Cells die at increasingly greater rates. B) Only older cells die in a culture. C) Cells in a culture die at a constant rate. D) Upon contact with the control agent, all cells die at one time. E) Cells become metabolically inactive, but are never killed.

C) Cells in a culture die at a constant rate.

In Table 3, which disinfectant was bactericidal? A) Doom B) K.O. C) Mortum D) Sterl E) The answer cannot be determined based on the information provided

C) Mortum

The use of chemical agents directly on exposed body surfaces to destroy or inhibit vegetative pathogens is known as: A) disinfection. B) sterilization. C) antisepsis. D) sanitization. E) ionization

C) antisepsis.

Which of the following substances is used for surgical hand scrubs? A) phenol B) chlorine bleach C) chlorhexidine D) soap E) glutaraldehyde

C) chlorhexidine

The preservation of beef jerky from microbial growth relies on which method of microbial control? A) filtration B) lyophilization C) desiccation D) ionizing radiation E) supercritical CO2

C) desiccation

Which of the following chemical agents is used for sterilization? A) alcohol B) phenolics C) ethylene oxide D) chlorine E) soap

C) ethylene oxide

Which of the following methods is used to preserve food by slowing the metabolic processes of foodborne microbes? A) lyophilization B) nonionizing radiation C) freezing D) ionizing radiation E) pasteurization

C) freezing

Which of the following is the best method to sterilize heat‐labile (sensitive) solutions? A) dry heat B) autoclave C) membrane filtration D) pasteurization E) freezing

C) membrane filtration

Which one of the following is most resistant to chemical disinfectants? A) Clostridium tetani endospores B) gram‐positive bacteria C) mycobacteria D) protozoan cysts E) viruses with lipid envelopes

C) mycobacteria

Which of the following is a limitation of the autoclave? A) It requires an excessively long time to achieve sterilization. B) It cannot inactivate viruses. C) It cannot kill endospores. D) It cannot be used with heat‐labile materials. E) It cannot be used with glassware.

D) It cannot be used with heat‐labile materials.Add... Add...

Which of the following microbial forms have the highest resistance to physical and chemical controls? A) naked viruses B) protozoan cysts C) fungal spores D) bacterial endospores E) yeast

D) bacterial endospores

Which graph in Figure 2 best depicts the effect of placing the E. coli culture at 4°C at time x? A) a B) b C) c D) d E) e

D) d

Application of heat to living cells can result in all of the following EXCEPT A) breaking of hydrogen bonds. B) alteration of membrane permeability. C) denaturation of enzymes. D) decreased thermal death time. E) damage to nucleic acids.

D) decreased thermal death time.

Ethylene oxide A) is a good antiseptic. B) is not sporicidal. C) requires high heat to be effective. D) is a sterilizing agent. E) is the active chemical in household bleach.

D) is a sterilizing agent.

Hydrogen peroxide can be A) sporicidal. B) fungicidal. C) bactericidal. D) virucidal. E) All of the choices are correct.

E) All of the choices are correct.

Which of the following factors will influence the action of microbial agents? A) the number of microorganisms B) the kind of microorganisms C) temperature and pH D) mode and dosage of the agent E) All of these will influence the action.

E) All of these will influence the action.

Which of the following statements regarding antimicrobial control agents is FALSE? A) Contaminating organic debris such as blood or sputum decrease effectiveness. B) Some agents kill by denaturing microbial cell proteins. C) Some agents affect microbial cell membranes by disrupting lipids. D) Silver can be used for treating antibiotic‐resistant bacteria. E) Some agents inactivate prions by inactivating their DNA.

E) Some agents inactivate prions by inactivating their DNA.

In Figure 1, the thermal death point for this culture is A) 15 minutes. B) 50°C. C) 30 minutes. D) 170°C. E) The answer cannot be determined based on the information provided

E) The answer cannot be determined based on the information provided

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 1, what is the thermal death of Escherchia coli ? A) 150°C B) 60 minutes C) 120 minutes D) 100°C E) The answer cannot be determined based on the information provided.

E) The answer cannot be determined based on the information provided.

In Table 1, which compound was bactericidal? A) A B) B C) C D) D E) The answer cannot be determined based on the information provided.

E) The answer cannot be determined based on the information provided.

In Table 1, which compound was the most effective against E. coli? A) A B) B C) C D) D E) The answer cannot be determined based on the information provided.

E) The answer cannot be determined based on the information provided.

In Table 3, which disinfectant was most effective against Salmonella? A) Doom B) K.O. C) Mortum D) Sterl E) The answer cannot be determined based on the information provided.

E) The answer cannot be determined based on the information provided.

Electrons are ejected from atoms in cells when organisms are exposed to A) desiccation. B) ultraviolet light. C) ethyl alcohol. D) hydrogen peroxide. E) X rays.

E) X rays.

Each of the following is a common target of antimicrobial agents except A) cell walls. B) cell membranes. C) ribosomes. D) cellular proteins. E) cytoplasm.

E) cytoplasm.

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

E) heat, radiation, and some chemicals

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) boiling for one hour C) hydrogen peroxide D) oven at 121°C for one hour E) pressure cooker at 121°C for 15 minutes

E) pressure cooker at 121°C for 15 minutes