Ch 7 Multiple Choice

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

70%

Which one of the following is most resistant to chemical biocides? A) Gram-negative bacteria B) Gram-positive bacteria C) Mycobacteria D) Protozoan cysts E) Viruses with lipid envelopes

Mycobacteria

If you were preparing nutrient agar at home and didn't have an autoclave, what could you use to sterilize the nutrient agar? A) Bleach B) Boiling for 1 hour C) Hydrogen peroxide D) Oven at 121°C for 1 hour E) Pressure cooker at 121°C for 15 minutes

Pressure cooker (at 121°C for 15 minutes)

The antimicrobial activity of chlorine is due to which of the following? A) The formation of hypochlorous acid B) The formation of hydrochloric acid C) The formation of ozone D) The formation of free O E) Disruption of the plasma membrane

The formation of hypochlorous acid

A classmate is trying to determine how a disinfectant might kill cells. You observed that when he spilled the disinfectant in your reduced litmus milk, the litmus turned blue again. You suggest to your classmate that a. the disinfectant might inhibit cell wall synthesis. b. the disinfectant might oxidize molecules. c. the disinfectant might inhibit protein synthesis. d. the disinfectant might denature proteins. e. he take his work away from yours.

b

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? Figure 7.3 A) a B) b C) c D) d E) e

b

Which disinfectant(s) is (are) bactericidal? a. A, B, C, and D b. A, C, and D c. A only d. B only e. none of the above

b

Which of the following is most effective for sterilizing mattresses and plastic Petri dishes? a. chlorine b. ethylene oxide c. glutaraldehyde d. autoclaving e. nonionizing radiation

b

Which of the following is most likely to be bactericidal? a. membrane filtration b. ionizing radiation c. lyophilization (freeze-drying) d. deep-freezing e. all of the above

b

Which of the following is not a characteristic of quaternary ammonium compounds? a. bactericidal against gram-positive bacteria b. sporicidal c. amoebicidal d. fungicidal e. kills enveloped viruses

b

Which of the following could be used to sterilize plastic Petri plates in a plastic wrapper? A) Autoclave B) Gamma radiation C) Microwaves D) Sunlight E) Ultraviolet radiation

gamma radiation

Which of the following is NOT used to disinfect water? A) Ozone B) Gamma radiation C) Chlorine D) Copper sulfate E) Heat

heat

Which of the following will NOT inactivate endospores? A) Autoclave B) Chlorine dioxide C) High pressure D) Plasma E) Supercritical CO2

high pressure

Glutaraldehyde is considered one of the most effective disinfectants for hospital use. Which of the following statements about glutaraldehyde is false? A) Stains and corrodes B) Is safe to transport C) Acts rapidly D) Is not hampered by organic material E) Attacks all microorganisms

stains and corrodes

Which of these disinfectants acts by denaturing proteins? A) Alcohols B) Aldehydes C) Bisphenols D) Halogens E) Phenolics

bisphenols

Which of the following will NOT destroy prions? A) Boiling B) Incineration C) NaOH + autoclaving at 134°C D) Proteases E) All of the above destroy prions.

boiling

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? A) a B) b C) c D) a and b E) b and c

c

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. 23) In Figure 7.2, the thermal death point for this culture is A) 15 min. B) 50°C. C) 30 min. D) 170°C. E) Can't tell

can't tell

Which of the following is a limitation of the autoclave? A) Requires a long time to achieve sterilization B) Cannot inactivate viruses C) Cannot kill endospores D) Cannot be used with heat-labile materials E) Cannot be used with glassware

cannot be used with heat-labile materials

Which of the following does NOT directly result from application of heat? A) Breaking of hydrogen bonds B) Breaking of sulfhydryl bonds C) Denaturing of enzymes D) Cell lysis E) Damage to nucleic acids

cell lysis

Which of the following substances is used for surgical hand scrubs? A) Phenol B) Chlorine bleach C) Chlorhexidine D) Soap E) Glutaraldehyde

chlorhexidine

Which of the following substances can sterilize? A) Alcohol B) Phenolics C) Ethylene oxide D) Chlorine E) Soap

ethylene oxide

In Figure 7.2, the decimal reduction time (D value) for the culture is approximately A) 0 min. B) 15 min. C) 30 min. D) 45 min. E) 60 min.

15 min.

Place the following surfactants in order from the most effective to the least effective antimicrobial activity: 1-Soap 2-Acid-anionic detergent 3-Quats A) 1, 2, 3 B) 1, 3, 2 C) 2, 1, 3 D) 3, 2, 1 E) 3, 1, 2

3, 2, 1

In Figure 7.1, what is the thermal death time for culture (a)? A) 150°C B) 60 min C) 120 min D) 100°C E) Can't tell

60 min

In Figure 7.2, the thermal death time for this culture is A) 0 min. B) 10 min. C) 20 min. D) 40 min. E) 60 min.

60 min.

Which one of the following does NOT belong with the others? A) Acid-anionic detergents B) Benzoic acid C) Supercritical CO2 D) Pasteurization E) Peracetic acid

Acid-anionic detergents

The following data Table 7.3 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) Doom K.O. Dilution Initial Subculture Initial Subculture 1:16 - + + + 1:32 - + + + 1:64 - + + + 1:128 + + + + Mortum Sterl Dilution Initial Subculture Initial Subculture 1:16 - - - + 1:32 - + + + 1:64 + + + + 1:128 + + + + 36) In Table 7.3, which disinfectant is the most effective at stopping bacterial growth? A) Doom B) K.O. C) Mortum D) Sterl E) Can't tell

Answer: A

The fate of E. coli O157:H7 in apple cider held at 8°C for 2 weeks, with and without preservatives, is shown below: Table 7.2 Bacteria/ml Cider only 2.2 Cider with potassium sorbate 2.0 Sodium benzoate 0 Sorbate + benzoate 0 32) In Table 7.2, which preservative is most effective? A) Sorbate B) Benzoate C) Sorbate + benzoate D) No preservative

Answer: B

A disk-diffusion test using Staphylococcus gave the following results: Table 7.1 Disinfectant Zone of inhibition (mm) A 0 B 2.5 C 10 D 5 29) In Table 7.1, which compound was the most effective against Staphylococcus? A) A B) B C) C D) D E) Can't tell

Answer: C

The following data Table 7.3 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) Doom K.O. Dilution Initial Subculture Initial Subculture 1:16 - + + + 1:32 - + + + 1:64 - + + + 1:128 + + + + Mortum Sterl Dilution Initial Subculture Initial Subculture 1:16 - - - + 1:32 - + + + 1:64 + + + + 1:128 + + + + In Table 7.3, which disinfectant was bactericidal? A) Doom B) K.O. C) Mortum D) Sterl E) Can't tell

Answer: C

A disk-diffusion test using Staphylococcus gave the following results: Table 7.1 Disinfectant Zone of inhibition (mm) A 0 B 2.5 C 10 D 5 In Table 7.1, which compound was bactericidal? A) A B) B C) C D) D E) Can't tell

Answer: E

A disk-diffusion test using Staphylococcus gave the following results: Table 7.1 Disinfectant Zone of inhibition (mm) A 0 B 2.5 C 10 D 5 In Table 7.1, which compound was the most effective against E. coli? A) A B) B C) C D) D E) Can't tell

Answer: E

The following data Table 7.3 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) Doom K.O. Dilution Initial Subculture Initial Subculture 1:16 - + + + 1:32 - + + + 1:64 - + + + 1:128 + + + + Mortum Sterl Dilution Initial Subculture Initial Subculture 1:16 - - - + 1:32 - + + + 1:64 + + + + 1:128 + + + + In Table 7.3, which disinfectant was most effective against Salmonella? A) Doom B) K.O. C) Mortum D) Sterl E) Can't tell

Answer: E

Which of the following substances is NOT used to preserve foods? A) Biguanides B) Nisin C) Potassium sorbate D) Sodium nitrite E) Sodium propionate

Biguanides

Which graph in Figure 7.3 best depicts the effect of placing the culture at 7°C at time x? A) a B) b C) c D) d E) e

D

Which of the following substances is NOT an oxidizing agent? A) Chlorine B) Glutaraldehyde C) Hydrogen peroxide D) Iodine E) Ozone

Glutaraldehyde

Which one of the following does NOT belong with the others? A) Beta-propiolactone B) Glutaraldehyde C) Ethylene oxide D) Hydrogen peroxide E) Propylene oxide

Hydrogen peroxide

Bone and tendons for transplant are decontaminated by A) Ethylene oxide. B) Glutaraldehyde. C) Peroxygens. D) Plasma sterilization. E) Supercritical fluids.

Supercritical fluids

Which of the following best describes the pattern of microbial 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.

The cells in a population die at a constant rate

Which one of the following pairs is mismatched? A) Ionizing radiation - hydroxyl radicals B) Ozone - takes electrons from substances C) Plasma sterilization - free radicals D) Supercritical fluids - CO2 E) Ultraviolet radiation - desiccation

Ultraviolet radiation - desiccation

Which disinfectant is the most effective?

a

Which of the following is used to control microbial growth in foods? a. organic acids b. alcohols c. aldehydes d. heavy metals e. all of the above

a

Which of the following substances is NOT effective against nonenveloped viruses? A) Alcohol B) Chlorine C) Ethylene oxide D) Ozone E) All are equally effective.

alcohol

Which of the following pairs is mismatched? A) Ag - burns B) Alcohols - open wounds C) CuSO4 - algicide D) H2O2 - open wounds E) Organic acids - food preservation

alcohols - open wounds

Which of the following treatments is the most effective for controlling microbial growth? A) 63°C for 30 min. B) 72°C for 15 sec. C) 140°C for 4 sec. D) all 3 are equivalent E) None is effective.

all 3 are equivalent

Iodophors differ from iodine (I2) in that iodophors A) Don't stain. B) Are less irritating. C) Are longer lasting. D) Are combined with a nonionic detergent. E) All of the above.

all of the above

Which of the following affects the elimination of bacteria from an object? A) Number of bacteria present B) Temperature C) pH D) Presence of organic matter E) All of the above

all of the above

Which of the following is NOT a factor contributing to hospital-acquired infections? A) Some bacteria metabolize disinfectants. B) Gram-negative bacteria are often resistant to disinfectants. C) Invasive procedures can provide a portal of entry for bacteria. D) Bacteria may be present in commercial products such as mouthwash. E) All of the above

all of the above

Which of the following cannot be used to sterilize a heat-labile solution stored in a plastic container? a. gamma radiation b. ethylene oxide c. supercritical f luids d. autoclaving e. short-wavelength radiation

d

Which of the following does not kill endospores? a. autoclaving b. incineration c. hot-air sterilization d. pasteurization e. All of the above kill endospores.

d

Which of these disinfectants does not act by disrupting the plasma membrane? a. phenolics b. phenol c. quats d. halogens e. biguanides

d

Which of the following is the best method to sterilize heat-labile solutions? A) Dry heat B) Autoclave C) Membrane filtration D) Pasteurization E) Freezing

membrane filtration

Which of the following will NOT preserve foods? A) Desiccation B) High pressure C) Ionizing radiation D) Microwaves E) Osmotic pressure

microwaves

Which of the following does NOT achieve sterilization? A) Dry heat B) Pasteurization C) Autoclave D) Formaldehyde E) Ethylene oxide

pasteurization