Ch. 7 Flashcards


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1

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

C

2

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.

A

3

Which of the following chemical agents is used for sterilization?

A) alcohol

B) phenolics

C) ethylene oxide

D) chlorine

E) soap

C

4

Which of the following substances is used for surgical hand scrubs?

A) phenol
B) chlorine bleach

C) chlorhexidine

D) soap
E) glutaraldehyde

C

5

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

A

6

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 a hypochlorite ion E) disruption of the plasma membrane

A

7

Which of the following 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 dissolving lipids.

D) Silver is used for treating antibiotic-resistant bacteria.

E) Alcohols effectively inactivate nonenveloped viruses by attacking lipids.

E

8

Which of the following does NOT achieve sterilization?
A) dry heat
B) pasteurization
C) autoclave
D) supercritical fluids
E) ethylene oxide

B

9

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

10

An agent used to reduce the number of bacteria on a toilet would most accurately be called a(n)

Disinfectant

11

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

12

Which of the following disinfectants acts by disrupting the plasma membrane?

A) soaps
B) aldehydes
C) bisphenols
D) halogens
E) heavy metals

C

13

Oxidizing agents include all of the following EXCEPT A) chlorine.
B) glutaraldehyde.
C) hydrogen peroxide.
D) iodine.
E) ozone.

B

14

Disinfection of water is achieved by all of the following EXCEPT

A) ozone.

B) UV radiation.

C) chlorine.

D) copper sulfate.

E) peracetic acid.

E

15

All of the following substances are effective against nonenveloped viruses EXCEPT

Alcohol

16

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

17

Which concentration of ethanol is the most effective bactericide?

A) 100 percent

B) 70 percent

C) 50 percent

D) 40 percent

E) 30 percent

B

18

All of the following factors contribute to hospital-acquired infections EXCEPT

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) None of the answers is correct; all of these factors may contribute to hospital-acquired infection.

E

19

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

A) 63C for 30 minutes
B) 72C for 15 seconds
C) 140C for 4 seconds
D) They are equivalent treatments. E) None of the answers is correct.

D

20

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

B

21

Which of the following regarding antimicrobial control agents is FALSE?

A) Contaminating organic debris such as blood or sputum will

decrease effectiveness.
B) Some agents kill by denaturing microbial cell proteins.

C) Some agents affect microbial cell membranes by dissolving lipids.

D) Some agents are utilized as both an antiseptic and a disinfectant.

E) A true antimicrobial control agent is equally effective against both bacteria and viruses.

E

22

A suspension of 106 Bacillus cereus endospores was put in a hot- air oven at 170C. Plate counts were used to determine the number of endospores surviving at the time intervals shown.

22) In Figure 7.1, what is the thermal death time? A) 150C
B) 60 minutes
C) 120 minutes

D) 100C

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

B

23

In Figure 7.1, the decimal reduction time (D value) for the culture, which is defined as the time to reduce a population by one log, is approximately

A) 0 minutes.

B) 10 minutes.

C) 30 minutes.

D) 40 minutes.

E) 60 minutes.

B

24

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

25

An iodophor is a(n)

A) phenol.

B) agent that reduces oxygen.

C) quaternary ammonium compound.

D) form of formaldehyde.

E) iodine mixed with a surfactant.

E

26

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

27

All of the following substances are used to preserve foods EXCEPT

A) biguanides.

B) nisin.

C) potassium sorbate.

D) sodium nitrite.
E) calcium propionate.

A

28

All of the following are effective for destroying prions EXCEPT

A) boiling.
B) incineration.
C) NaOH + autoclaving at 134C.

D) proteases.

E) None of the answers are correct; each of these will destroy prions.

A

29

Which 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

E

30

All of the following are methods of food preservation EXCEPT

A) desiccation.
B) high pressure.
C) ionizing radiation. D) microwaves.
E) osmotic pressure.

D

31

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

32

Bone and tendons for transplant are decontaminated by A) ethylene oxide.
B) glutaraldehyde.
C) peroxygens.

D) plasma sterilization.

E) supercritical fluids.

E

33

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

A) gram-negative bacteria

B) gram-positive bacteria

C) mycobacteria
D) protozoan cysts

A

34

The following is true of quarternary ammonium compounds EXCEPT

A) they are non-toxic at lower concentrations.

B) they are tasteless.
C) they are effective when combined with soaps.

D) they are stable.

E) they may be an ingredient in mouthwash.

C

35

Any process that destroys the non-spore forming contaminants on inanimate objects is sterilization.

False

36

Desiccation is a reliable form of sterilization.

false

37

The thermal death time is the time needed to kill all the bacteria in a particular culture at a certain temperature.

True

38

Pseudomonas has been found growing in quaternary ammonium compounds (quats).

true

39

Moist heat destroys organisms by denaturing proteins.

true

40

Some antimicrobial chemicals are considered to be disinfectants and antiseptics.

true

41

The pH of the medium has no effect on the activity of the disinfectant being applied.

false

42

Ultraviolet light (UV) causes irreversible breaks in DNA strands.

false

43

Autoclaving is the most effective method of moist heat sterilization.

true

44

Microorganisms placed in high concentrations of salts and sugars undergo lysis.

false

45

Ethylene oxide is commonly used for the sterilisation of

A. fibre-optic endoscopes
B. glassware
C. rubber tubings and catheters

D. prosthetic cardiac valves

E. respiratory ventilators

D

46

The time between inoculation and the beginning of growth is usually called the

a) death phase

b) lag phase

c) log phase
d) dormant phase

B

47

Which of the following structures contains genes for enzymes and antibiotic resistance?

A. Plasmid

B. Pilus
C. Capsule
D. Plasma Membrane

A

48

Ultraviolet rays are used for sterilizing:

a. Operation rooms b. Beds
c. Hospital waste d. All of the above

D

49

Which of the following is the most widespread method of genetic transfer among bacteria
a. Transformation
b. Transduction

c. Lysogenic conversion

d. Conjugation

D

50

Which activity is an example of biotechnology?

A. bacteria in the soil secreting an antibiotic to kill competitors B. a microbiologist using the microscope to study bacteria
C. Egyptians using moldy bread on wounds
D. Eschericia coli producing human insulin

E. Public health officials monitoring diseases in a community

D

51

A microbiologist inoculates Staphylococcus epidermidis and Escherichia coli into a culture medium. Following incubation, only the E. coli grows in culture. What is the most likely explanation?
A. the microbiologist used too much inoculum
B. the culture is contaminated
C. the incubation temperature was incorrect
D. the culture medium must be selective
E. the culture medium must be differential

D

52

Which of the following best describes a plasmid?

a. A gene within the chromosome

b. Small circular piece of DNA outside the chromosome

c. The genetic material of a bacteriophage d. Part of bacterial ribosomes
e. A single, linear strand of DNA

B

53

If you were asked to sterilize a heat sensitive item which of the following would be most suitable?

  1. Steam autoclave
  2. Pasteurization
  3. Ethylene oxide
  4. Ethyl alcohol
  5. Hot air oven

C

54

A useful method or compound for sterilizing foods such as fresh vegetables: a. Ionizing radiation
b. Ultraviolet light
c. Steam autoclave

d. Phenols
e. Formaldehyde

A

55

Which of the following is commonly used to prepare incision sites for surgery and as a surgical scrub?
a. Ethyl alcohol
b. Hydrogen peroxide

c. Iodophor

d. Glutaraldehyde

e. Lysol

D

56

A chemical or physical agent that kills disease-causing microorganisms. Generally used on inanimate objects

a. disinfectant

b. antiseptic c. alcohol
d. sterilant

A

57

The process of completely removing or destroying all life forms or their products on or in a substance.
a. disinfection
b. antisepsis

c. sterilization

d. scrubbing

C

58

Which of the following infectious agents challenge the current sterilization strategies that have been accepted and in use for decades?

A) HIV

B) prions

C) endospores

D) mycobacteria

B

59

Major targets for action of antimicrobials:

A) enzymes

B) proteins

C) cell membranes

D) nucleic acids

E) all of the above

E

60

Pasteurized milk in an unopened container spoils in the refrigerator. A sample reveals the presence of microorganisms. The most likely explanation is __________.

A) pasteurization-resistant mutants developed after pasteurization

B) the pasteurization process was ineffective

C) the microbes are pathogens

D) the microbes that survived pasteurization were able to grow at 4°C.

D

61

Which of the following is LEAST likely to be damaged by exposure to gamma radiation?

A) prions

B) viruses

C) bacteria

D) fungi

A

62

The DRT for a particular bacterial species at 60°C is 30 minutes. How long would it take at this temperature to remove 99.9% of this bacterial population?

A) 10 minutes

B) 30 minutes

C) 60 minutes

D) 90 minutes

D

63

__________ is a compound found in antimicrobial soaps that targets gram-positive bacteria.

A) Formaldehyde

B) Hydrogen Peroxide

C) Triclosan

D) Sodium nitrate

C

64

You discover a compound that you suspect reduces spoilage in fruit. You treat apples with your compound and inoculate them with Botrytis, a common spoilage fungus. After 7 days, the dry weight of fungi is 5 mg on the treated apples and 10 mg on the untreated apples. You conclude from these results that __________.

A) apple spoilage is caused by fungi

B) compound is fungisatic

C) fungus probably will have no effect on the apples

D) the compound kills fungi

B

65

The presence of organic matter, such as blood or saliva, may impair the action of antimicrobial chemicals.

True

66

_______ bacteria may survive pasteurization

A) Thermoduric

B) Endospore-forming

C) Heat-resistant

D) Endospore forming

E) all of the above

E

67

Which one of these substances is effective against bacterial endospores?

A) mercury

B) hexachlorphene

C) biguanide

D) chlorine bleach

D

68

Which of the following represents a chemical that is NOT an oxidizing agent and also would NOT be effective in killing the organism paired with it?

A) hypochlorite; cysts of protozoa

B) chlorine; Mycobacterium tuberculosis

C) triclosan; E. coli

D) hydrogen peroxide; Clostridium endospores

C

69

Ethylene oxide gas is used to sterilize medical equipment that might be damaged by exposure to the heat of autoclaving.

True

70

Iodine is one of the LEAST effective antimicrobial chemicals, effective only against certain very sensitive strains of bacteria.

False

71

Most viruses are highly resistant to disinfectants and antiseptics.

False

72

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

A

73

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

D

74

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

C

75
  1. 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

A

76
  1. Which of the following is NOT used to disinfect water? A) Ozone B) Gamma radiation C) ChlorineD) Copper sulfateE) Heat

E

77
  1. Which of the following substances is NOT an oxidizing agent? A) Chlorine B) GlutaraldehydeC) Hydrogen peroxide D) IodineE) Ozone

B

78

Which of the following is not a possible reason why cells enter stationary phase?
a. they are running out of an essential nutrient
b. they are running out of oxygen
c. the accumulation of toxic waste products
d. the population has reached a critical size limit
e. actually all of these are possible reasons

E

79

Superoxide dismutase is an enzyme that catalyzes the conversion of oxygen radicals to peroxides. Which groups of organisms do not have this enzyme?

A. aerobes
B. facultative anaerobes

C. oxyduric anaerobes

D. oxylabile anaerobes

C

80

Identify the correct statement(s). In prokaryotes:
A. Translation begins before transcription is finished.
B. Messanger RNA is not co-linear with the DNA template.
C. 5s, 16s, and 28s ribosomal RNA's are present.
D. 50s and 30s ribosomal subunits are necessary for protein synthesis.
E. mRNA is monocistronic

A

81

Agar is an excellent solidifying agent for microbiological media because

A. it is not degraded by most microorganisms.

B. solid agar remains solid until the temperature is raised to 90C, and liquid agar remains liquid if the temperature is lowered to 45C.

C. it is not degraded by most microorganisms and solid agar remains solid until the temperature is raised to 90C, and liquid agar remains liquid if the temperature is lowered to 45C are correct.

D. agar provides an excellent source of nutrition for a variety of different microorganisms

C

82

Which of the following can be used to isolate pure cultures of bacteria from mixtures?

A. spread plates

B. streak plates

C. pour plates

D. all of the choices

D

83

Clostridium rubrum is an obligate anaerobe and E. coli is a facultative anaerobe. Which of the following statements is true? a) E. coli would be less likely than Clostridium to have the enzyme superoxide dismutase

b) E. coli would be less likely than Clostridium to grow in a candle jar

c) E. coli would grow at the bottom of a thioglycollate tube while Clostridium would grow at the top

d) E. coli would be more likely to reduce nitrate to nitrite than Clostridium

e) E. coli would be typically found under deep sediment layers under bodies of water while Clostridium would be typically found in surface wate

D

84

When antiseptics and disinfectants are compared, antiseptics are generally ________.
A) less toxic
B) more toxic
C) equally as toxic
D) unpredictable in toxicity

A

85

All germicides are capable of killing all pathogenic organisms and endospores. True or false.

false

86

The prevention of infection caused by microorganisms is called ________.
A) disinfection
B) antisepsis
C) sterilization
D) sanitization

B

87

The time required to kill 90% of the microorganisms or spores in a sample at a specified temperature is the ________.
A) thermal death time (TDT)
B) thermal death point (TDP)
C) decimal reduction time (D value)
D) z value

C

88

Which of the following influence(s) the efficiency of an antimicrobial agent?
A) Concentration of the agent
B) Duration of exposure
C) Temperature
D) All of the choices are correct.

D

89

Which of the following environmental factors generally do(es) not have an impact on the efficiency of an antimicrobial agent?
A) pH
B) Presence or absence of a biofilm
C) Concentration of organic matter
D) Refractive index

D

90

Which of the following is MOST effective against resistant endospores?
A) Autoclaving
B) Boiling
C) Pasteurization
D) All of these are equally effective against resistant endospores.

A

91

Moist heat sterilization at 100°C kills all of the following EXCEPT ________.
A) bacterial endospores
B) fungal spores
C) viruses
D) protists

C

92

When comparing dry heat and moist heat sterilization, dry heat is ________.
A) faster
B) slower
C) equally as fast
D) sometimes faster but sometimes slower

B

93

Which kind of sterilization procedure takes advantage of the size of microorganisms?
A) Autoclaving
B) Open flame
C) Use of chemicals
D) Filtration

D

94

Dry heat methods usually require lower temperatures and shorter exposure times than moist heat methods to achieve the same degree of killing because of the drying effects of this form of heat. True or false.

false

95

Which of the following is a function of pasteurization?
A) Killing pathogenic microorganisms
B) Reducing the total microbial population
C) Increasing the shelf life of the product
D) All of the choices are correct.

D

96

Which of these is an agent that is used to sterilize the plastic tubing of heart-lung machines?
A) Phenol
B) Mercaptoethanol
C) Ethylene oxide
D) 70% ethanol

C

97

Heavy metals may inactivate proteins by reacting with their sulfhydryl groups. True or false.

true

98

Alcohols are widely used as antiseptics and disinfectants because they are effective against endospores as well as vegetative cells. True or false.

false

99

Heavy metals are effective antimicrobial agents but are not widely used because of their high toxicity to humans. True or false.

true

100

The disinfecting properties of Lysol, a common household disinfectant, depend upon the presence of ________.

phenolics

101

The disinfectant of choice for municipal water supplies is ________.
A) fluorine
B) chlorine
C) either fluorine or chlorine
D) ultraviolet light

B

102

Several new materials have been developed for use in the microbiology lab. These materials must be sterilized before use, but cannot withstand a temperature over 60oC and can't be exposed to water. Which method of sterilization would be applicable?
A) Steam autoclave
B) Oven-dry heat
C) UV radiation
D) Ionizing radiation

D

103

Which of the following would be most effective and practical for routine home disinfection of a toothbrush between uses?
A) 70% Isopropyl alcohol
B) Glutaraldehyde
C) Bleach
D) Hydrogen peroxide

D