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Exam 3, Chapter 7

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The Control Of Microbial Growth

updated 3 years ago by Tish

Grade levels:
College: First year, College: Second year, College: Third year, College: Fourth year

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1

THE TERMINOLOGY OF MICROBIAL CONTROL

Aseptic Surgery

Techniques used in surgery to prevent microbial contamination from the instruments, operating personnel, and the patient.

2

THE TERMINOLOGY OF MICROBIAL CONTROL

Sterilization

The destruction or removal of all microbial life, including endospores.

3

THE TERMINOLOGY OF MICROBIAL CONTROL

How do you sterilize liquids or gases?

By using filtration.

4

THE TERMINOLOGY OF MICROBIAL CONTROL

Sterilant

Is a sterilizing agent.

5

THE TERMINOLOGY OF MICROBIAL CONTROL

Commercial Sterilization

The process of treating canned goods aimed at destroying the endospores of Clostridium botulinum (a kind of food poisoning).

6

THE TERMINOLOGY OF MICROBIAL CONTROL

Why is commercial sterilization important?

Clostridium botulinum produces a deadly toxin. More-resistant endospores of thermophilic (heat-loving) bacteria are capable of causing food spoilage but not human disease, and they will not germinate and grow at normal food storage temperatures.

7

THE TERMINOLOGY OF MICROBIAL CONTROL

Disinfection

Any treatment used on inanimate objects to kill or inhibit the growth of microorganisms; removing pathogens.

8

THE TERMINOLOGY OF MICROBIAL CONTROL

Antisepsis

A chemical method for disinfection of the skin and mucous membranes; removing pathogens from living tissues.

9

THE TERMINOLOGY OF MICROBIAL CONTROL

Antiseptic

Is the chemical used to perform the antisepsis technique.

10

THE TERMINOLOGY OF MICROBIAL CONTROL

Sepsis

The presence of a toxin or pathogenic organism in blood and tissue; refers to microbial contamination.

11

THE TERMINOLOGY OF MICROBIAL CONTROL

Asepsis

The absence of contamination by unwanted organisms.

12

THE TERMINOLOGY OF MICROBIAL CONTROL

Degerming

The mechanical removal of microorganisms in an area or injection site, rather than killing them; also called degermation.

13

THE TERMINOLOGY OF MICROBIAL CONTROL

Sanitization

The removal of microorganisms from eating utensils and food preparation areas.

14

Biocide, or Germicide

A substance capable of killing microorganisms (except endospores).

15

THE TERMINOLOGY OF MICROBIAL CONTROL

Suffix -cide

Names of treatments that cause the outright death of microbes; meaning kill.

16

Bacteriostasis

A treatment capable of inhibiting bacterial growth.

17

EFFECTIVENESS OF TREATMENT

Depends on:

1. The number of microbes.

2. Environment (organic matter, temperature,
biofilms).

3. The time of exposure.

4. Microbial characteristics.

18

ACTION OF MICROBIAL CONTROL AGENTS

1. Alterations of membrane permeability.

2. Damage to proteins.

3. Damage to nucleic acids.

19

HEAT

Thermal death point (TDP)

The temperature required to kill all the bacteria in a liquid culture in 10 minutes.

20

HEAT

Thermal death time (TDT)

The length of time required to kill all bacteria in a liquid culture at a given temperature.

21

HEAT

Decimal reduction time (DRT)

The time (in minutes) required to kill 90% of a bacterial population at a given temperature; also called D value.

22

MOIST HEAT STERILIZATION

Moist heat denatures proteins.

23

MOIST HEAT STERILIZATION

Autoclave

Equipment for sterilization by steam under pressure; usually operated at 15 psi and 121°C to kill all organisms (except prions)and their endospores in about 15 minutes; guaranteed complete sterilization.

24

Pasteurization

The process of mild heating to kill particular spoilage microorganism or pathogens; normal pasteurization is 63°C for 30 minutes; does not achieve complete sterilization only reduces microbes.

25

PASTEURIZATION

1. Reduces spoilage organisms and pathogens.

2. EQUIVALENT TREATMENTS:
a) 63°C for 30 min
b) High-temperature short-time
c) Ultra-high-temperature
d) Thermoduric organisms survive

26

PASTEURIZATION

High-temperature short-time (HTST) pasteurization

Pasteurization at 72°C for 15 seconds.

27

PASTEURIZATION

Ultra-high-temperature (UHT)treatments

A method of treating food with high temperatures (140-150°C for 4 seconds) for very short times to make food sterile so that it can be stored at room temperature.

28

What are the differences between HTST and UHT?

1. HTST is pasteurization and has to be
refrigerated for a certain amount of time
(usually 2 weeks) before it spoils.

2. UHT is sterilized and can be stored for several
months without refrigeration; an example is
the small coffee creamers found in restaurants.

29

Thermoduric bacteria

Heat resistant; survive pasteurization; unlikely to cause disease or cause refrigerated milk to spoil.

30

DRY HEAT STERILIZATION

Kills by:

1. Dry heat

2. Flaming

3. Incineration

4. Hot-air sterilization

31

DRY HEAT STERILIZATION

Dry heat

Kills by oxidation effects.

32

DRY HEAT STERILIZATION

Flaming

The process of sterilizing an inoculating loop by holding it in an open flame.

33

DRY HEAT STERILIZATION

Incineration

Burning to ashes.

34

DRY HEAT STERILIZATION

Hot-air sterilization

Sterilization by the use of an oven at 170°C for approximately 2 hours.

35

DRY HEAT STERILIZATION

Equivalent treatments

Different methods that have the same effect on controlling microbial growth.

36

FILTRATION

The passage of a liquid or gas through a screenlike material; a 0.45µm filter removes most bacteria; heat labile (sensitive)substances should be sterilized by filtration and not heat.

37

FILTRATION

High-efficiency particulate air (HEPA) filters

A screenlike material that removes particles greater than 0.3µm from air.

38

FILTRATION

Membrane filters

A screen-like material with pores small enough to remove microbes greater than 0.22µm from air; a 0.45µm filter retains most bacteria; used for liquids.

39

FILTRATION

Filterable viruses

Unseen pathogens that passed through the filters (causing such disease as rabies) made of unglazed porcelain in the early days of microbiology.

40

PHYSICAL METHODS OF MICROBIAL CONTROL

Kills by:

1. Low temperature

2. High pressure

3. Desiccation

4. Osmotic pressure

41

PHYSICAL METHODS OF MICROBIAL CONTROL

Low temperature

1. Creates a bacteriostatic effect at temperatures of ordinary refrigerators (0-7°C) because it reduces the metabolic rate of most microbes so that they cannot reproduce or synthesize toxins; rapidly attained subfreezing temperatures tend to render microbes dormant but do not necessarily kill them.

2. INHIBITS MICROBIAL GROWTH:
a) Refrigeration
b) Deep-freezing
c) Lyophilization

42

PHYSICAL METHODS OF MICROBIAL CONTROL

Lyophilization

In the absence of water (desiccation) microorganisms cannot grow or reproduce but can remain viable for years and then resume their growth and division once water is made available to them; also called freeze-drying, which is a laboratory process for preserving microbes.

43

PHYSICAL METHODS OF MICROBIAL CONTROL

High pressure

Denatures proteins

44

PHYSICAL METHODS OF MICROBIAL CONTROL

Desiccation

The removal of water; drying; prevents metabolism.

45

PHYSICAL METHODS OF MICROBIAL CONTROL

Osmotic pressure

High concentrations of salt and sugars causes PLASMOLYSIS which is the loss of water from a cell in a hypertonic environment; can't metabolize but inhibits their growth

46

RADIATION

Types:

1. Ionizing radiation

2. Nonionizing radiation

3. Microwaves

47

RADIATION

Ionizing radiation

1.Gamma rays, X rays, or High-energy electron
beams, has a wavelength shorter than that of
nonionizing radiation less than about 1nm.

2. Ionizes water to release OH.

3. Damages DNA.

48

RADIATION

Non-ionizing radiation

1. Short-wavelength radiation that does not cause
ionization; radiation is not very penetrating;
ultraviolet (UV) radiation (260nm) is an
example.

2. Damages DNA.

49

RADIATION

Microwaves

1. Electromagnetic radiation.

2. Kill by radiation; not especially antimicrobial.

50

PRINCIPLES OF EFFECTIVE DISINFECTION

1. Concentration

2. Organic matter

3. pH

4. Time

51

USE-DILUTION TEST

1. A method of determining the effectiveness of a
disinfectant using serial dilutions.

2. Metal rings dipped in test bacteria are dried.

3. Dried cultures are placed in disinfectant for 10 min at 20°C.

4. Rings are transferred to culture media to
determine whether bacteria survived treatment.

52

DISK-DIFFUSION METHOD

An agar-diffusion test to determine microbial susceptibility to chemotherapeutic agents; also called Kirby-Bauer test.

53

Phenol

Also called carbolic acid; first used by Lister to control surgical infections in the operating room.

54

Phenolics

A derivative of phenol used as a disinfectant.

55

PHENOL & PHENOLICS

Disrupt plasma membranes

56

Cresol

Phenolic derived from coal tar; are very good surface disinfectants.

57

Why are phenolics useful as disinfectants?

1. They remain active in the presence of organic
compounds.
2. They are stable.
3. They persist for long periods after
application.

58

Bisphenols

1. A derivative of phenol that contains two phenol
groups connected by a bridge (bis indicates
two).

2. HEXACHOLORPHENE, TRICLOSAN:
disrupt plasma membrane

59

Hexachlorophene

A type of bisphenol used to control infections in nurseries; excessive use on infants can lead to nerve damage.

60

Triclosan

A bisphenol used in antibacterial soaps, at least one toothpaste, and kitchen cutting boards and plastics; it inhibits an enzyme needed for the biosynthesis of fatty acids (lipids), which mainly affects the plasma membrane; effective againt gram positive bacteria and also works well against gram-negative bacteria.

61

Biguanides

CHLORHEXIDINE:
disrupt Plasma membrane

62

Chlorhexidine

A Biguanide used for microbial control on skin and mucous membranes.

63

Fungicide

A substance capable of killing fungi.

64

Virucide

A substance capable of inactivating viruses.

65

Suffix -stat or -stasis

Names of treatments that inhibit the growth and multiplication of bacteria; meaning to stop or to steady.

66

Several factors influence the effectiveness of antimicrobial treatments:

1. The number of microbes
2. Environmental influences:
a. Organic matter
b. Microbes in surface biofilms
c. Suspended medium
3. Time of exposure
4. Microbial characteristics

67

The number of microbes

The more microbes there are to begin with, the longer it takes to eliminate the entire population.

68

Environmental influences

Organic matter

Inhibits the action of chemical antimicrobials.

69

Environmental influences

Microbes in surface biofilms

Are difficult for biocides to reach effectively. Because their activity is due to temperature-dependent chemical reactions, disinfectants work somewhat better under warm conditions.

70

Environmental influences

Suspended in medium

Fats and proteins are especially protective, and a medium rich in these substances protect microbes, which will then have a higher survival rate.

71

Time of exposure

Chemical antimicrobials often require extended exposure to affect more-resistant microbes or endospores.

72

Microbial characteristics

Affect the choice of chemical and physical control methods.

73

Cell membrane permeability

This membrane actively regulates the passage of nutrients into the cell and the elimination of waste from the cell.

74

Functional properties of proteins

Are the result of their three-dimensional shape.

75

What physical methods are used as heat techniques?

1. Moist heat:
a) Boiling or flowing stream
b) Autoclaving

2. Pasteurization

3. Dry heat:
a) Direct flaming
b) Incineration
c) Hot-air sterilization

76

Retorts

A device for commercially sterilizing canned food by using steam under pressure; operates on the same principle as an autoclave but is much larger.

77

Boiling or flowing stream

Kills vegetative forms of bacterial pathogens, almost all viruses, and fungi and their spores within about 10 minutes; 100°C is considered boiling; does not kill endospores so it is not considered a complete sterilization.

78

What does the phosphate test, test for?

**phosphatase is an enzyme naturally present in milk**

To determine whether products have been pasteurized; phosphatase products will be inactived if the product has been pasteurized.

79

What types of bacteria and what types of virus can resist boiling? And for how long?

1. Some hepatitis viruses, can resist up to 30
minutes of boiling.

2. Some bacterial endospores, can resist boiling
for more than 20 hours.

80

Sterilization in an autoclave is most effective when?

1. The organisms are contacted by the steam
directly.

2. Or contained in a small volume of aqueous
(primarily water) liquid.

81

What physical methods are used as cold techniques?

1. Refrigeration

2. Deep-freezing

3. Lyophilization

82

Halogens

One of the following elements: fluorine, chlorine, bromine, iodine, or astatine.

83

HALOGENS-IODINE

Tincture

A solution in aqueous alcohol and is an iodophor.

84

HALOGENS-IODINE

Iodophors

A combination of iodine and an organic molecule, from which the iodine is released slowly; have the antimicrobial activity of iodine, but they do not stain and are less irritating.

85

HALOGENS

Chlorine

1. BLEACH:
Hypochlorous acid (HOCI)

2. CHLORAMINE:
Chlorine + ammonia

3. Oxidizing agents

86

Alcohols

1. An organic molecule with the functional group-
OH.

2. ETHANOL, ISOPROPANOL:
a) denature proteins, dissolve lipids
b) require water

87

Pseudomonas aeruginosa

A gram-negative bacteria that is very resistant to triclosan, and many other antibiotics and disinfectants.

88

HEAVY METALS

Ag, Hg, Cu

1. Silver Nitrate may be used to prevent
gonorrheal opthalmia neonatorum.

2. Silver Sulfadiazine used as a topical cream on
burns.

3. Copper Sulfate is an algicide.

89

HEAVY METALS

Oligodynamic action

The ability of small amounts of a heavy metal compound to exert antimicrobial activity; oligo means few; denatures proteins.

90

SURFACE-ACTIVE AGENTS, OR SURFACTANTS

Surface-active agents

Any compound that decreases the tension between molecules lying on the surface of a liquid; also called surfactant.

91

SURFACE-ACTIVE AGENTS, OR SURFACTANTS

Soap

Degerming

92

SURFACE-ACTIVE AGENTS, OR SURFACTANTS

Acid-anionic detergents

Sanitizing

93

SURFACE-ACTIVE AGENTS, OR SURFACTANTS

Quaternary ammonium compounds (cationic detergents)

Bactericidal, denature proteins, disrupt plasma membrane.

94

Quaternary ammonium compounds (quats)

A cationic detergent with four organic groups attached to a central nitrogen atom; used as a disinfectant; are less effective against gram-negative bacteria and more effective against gram positive bacteria.

95

Sulfar dioxide ( SO‚₂)

Disinfectant used in wine-making.

96

Sorbic acid, potassium sorbate, sodium benzoate

Prevent molds from growing on acidic foods, such as cheese and soft drinks.

97

Calcium propionate

An effective fungistat used in bread, prevents the growth of surface molds and the Bacillus bacterium that causes ropy bread.

98

Sodium nitrate and Sodium nitrite

Are added to many meat products, such as ham, bacon, hot dogs, and sausage.

99

How do the bacteria in meats use nitrate?

As a substitute for oxygen under anaerobic conditions.

100

What are the 2 main functions of nitrite?

1) To preserve the red color of the meat by reacting with blood components in the meat.

2) To prevent the germination and growth of any botulism endospores that might be present.

101

Nitrosamines

A carcinogen formed by the combination of nitrite and amino acids.

102

ALDEHYDES

1. An organic molecule with the functional group-
CHO.

2. Inactivates proteins by cross-linking with
functional groups (-NH₂, -OH, -COOH, -SH)

3. USE: MEDICAL EQUIPMENT
a) Glutaraldehyde, formaldehyde, and ortho-
phthalaldehyde.

103

GASEOUS STERILANTS

1. Denature proteins

2. USE: HEAT-SENSITIVE MATERIAL
a) Ethylene oxide

104

PLASMA

1. The liquid portion of blood in which the formed
elements are suspended.

2. Exited gases used for sterilization.

3. Free radicals destroy microbes.

4. USE: TUBULAR INSTRUMENTS

105

SUPERCRITICAL FLUIDS

1. CO₂with gaseous and liquid properties.

2. USE: MEDICAL IMPLANTS

106

PEROXYGENS

1. A class of oxidizing-type sterilizing
disinfectants.

2. Oxidizing agents.

3. USE: CONTAMINATED SURFACES
a) O3, H₂O₂, peracetic acid

107

CHEMICAL FOOD PRESERVATIVES

ORGANIC ACID

1. Inhibits metabolism.

2. Sorbic acid, benzoic acid, and calcium
propionate.

3. Control molds and bacteria in foods and
cosmetics.

108

CHEMICAL FOOD PRESERVATIVES

Nitrite

Prevents endospore germination.

109

CHEMICAL FOOD PRESERVATIVES

Antibiotics

Nisin and Natamycin prevent spoilage of cheese.

110

Nisin

Is often added to cheese to prevent the growth of certain endospore-forming spoilage bacteria.

111

Natamycin (primaricin)

Is an antifungal antibiotic approved for use in foods, mostly cheese.

112

MICROBIAL CHARACTERISTICS

IN ORDER FROM MOST RESISTANT TO LEAST RESISTANT:

Prions

Endospores of bacteria

Mycobacteria

Cysts of protozoa

Vegetative protozoa

Gram-negative bacteria

Fungi, including most fungal spores

Viruses without envelopes

Gram-positive bacteria

Viruses with lipid envelopes

113

Sterilization is the:

A) same as sanitization.
B) destruction of all forms of microbial life
except endospores.
C) effective removal of all microbes on a
surface.
D) destruction of all life forms.
E) control of all microbial growth.

Destruction of all life forms.

114

An antiseptic is used when one needs to remove microbes from:

A) food preparation areas.
B) foods, prior to canning.
C) toilet surfaces.
D) restaurant glassware.
E) skin, prior to injection.

Skin, prior to injection.

115

Foods to be canned need not be sterile. However, all ______ of Clostridium botulinum must be killed.

A) LPS
B) capsules
C) flagellar proteins
D) cells
E) endospores

Endospores

116

Some antimicrobial treatments kill microbes; some inhibit growth. Which term refers to an agent that inhibits bacterial growth?

A) Germicidal.
B) Bacteriostatic.
C) Fungicidal.
D) Homeostatic.
E) Bacteriocidal.

Bacteriostatic.

117

Which of the following is not a major target for action of antimicrobials?

A) Flagella.
B) Enzymes
C) Nucleic acids.
D) Cell membranes.
E) Proteins.

Flagella.

118

Decimal reduction time is the time in minutes in which _______ of the population at a given temperature will be killed.

A) 75%
B) 100%
C) 10%
D) 80%
E) 90%

90%

119

Which is not a characteristic of the autoclave?

A) The ability to sterilize solutions with
endospores.
B) The use of high temperatures.
C) The use of moist heat.
D) The use of high pressures.
E) The requirement for long (hours) exposure
times.

The requirement for long (hours) exposure times.

120

Milk that you have never opened spoils in the refrigerator. A sample reveals the presence of microorganisms. The most likely explanation is:

A) the pasteurization process was ineffective.
B) the microbes are pathogens.
C) the microbes that survived pasteurization were
able to grow at 4 °C.
D) there was a leak in the milk carton that
allowed microbes to enter.
E) pasteurization resistant mutants developed
after pasteurization.

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

121

Pasteurization was first used by Pasteur to control spoilage of:

A) canned foods.
B) cheese.
C) wine.
D) milk.
E) yogurt.

Wine.

122

Choose the best method for the sterilization of an enzyme solution.

A) Filtration.
B) Freezing.
C) Autoclave
D) Pasteurization.
E) Dry heat.

Filtration.

123

The bactericidal effect of UV light is attributed to damage to:

A) plasma membranes.
B) proteins.
C) nuclei.
D) DNA.
E) ribosomes.

DNA.

124

Packages of milk and coffee creamers may be stored without refrigeration if they have been sterilized by:

A) autoclaving.
B) high-temperature short-time (HTST)
pasteurization.
C) boiling.
D) ultra-high-temperature (UHT) treatment.
E) treatment with phenol.

Ultra-high-temperature (UHT) treatment.

125

All of the following methods are used for food preservation except:

A) Direct flaming.
B) Dessication.
C) Osmotic pressure.
D) Commercial canning.
E) Deep freezing.

Direct flaming.

126

Some microbes are very resistant to antimicrobial chemicals. Which of the following would be the easiest to kill?

A) E. coli.
B) Cysts of protozoa
C) Pseudomonas aeruginosa
D) Mycobacterium tuberculosis
E) Clostridium endospores

E. coli.

127

Which type of radiation is least effective in killing microbes?

A) Microwaves
B) Gamma rays
C) Ultraviolet rays
D) High-energy electron beams
E) X rays

Microwaves

128

The first disinfectant used by Lister was ________.

A) iodine.
B) chlorine.
C) Listerine.
D) Betadine.
E) phenol.

Phenol.

129

Alcohol is most effective when used as a solution.

A) 70%
B) 60%
C) 25%
D) 95%
E) 100%

70%

130

All of the following are examples of microbial control using heavy metals except:

A) antiseptic solution containing mercurochrome.
B) benzoyl peroxide used for acne treatment.
C) algae control in swimming pools using copper
sulfate.
D) burn treatment using silver-sulfadiazine
ointment.
E) mouthwash solution containing zinc chloride.

Benzoyl peroxide used for acne treatment.

131

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

A) Formaldehyde
B) Hydrogen peroxide
C) Sodium nitrate
D) Triclosan
E) Mercuric chloride

Triclosan.

132

The following may be listed on the ingredients of your favorite snack food. Which of the following is not antimicrobial?

A) Xanthan.
B) Calcium propionate.
C) Potassium sorbate.
D) Sorbic acid.
E) Sodium benzoate.

Xanthan.

133

Microbes vary with respect to sensitivity to an antimicrobial agent.

True.

134

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

False.

135

All bacteria die at once when they are exposed to heat or chemical treatment.

True.

136

Times required for sterilization in an autoclave are shorter than those required in a dry oven because moist heat penetrates biological specimens more effectively than does dry heat.

True.

137

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

True.

138

UV radiation and X ray radiation are similar in that they damage DNA and have a high penetrating power.

False.

139

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

False.

140

Soap is ineffective in killing bacteria. Therefore, hand washing is a rather ineffective measure in preventing disease transmission.

False.

141

Most disinfectants can be used as antiseptics.

False.

142

70% ethyl alcohol is a more effective bactericide than 100% alcohol.

True.

143
card image

According to the figure, at what rate are the cells dying?

A) 1% each minute
B) 10% each minute
C) 50% each minute
D) 90% each minute
E) 99% each minute

90% each minute

144
card image

In the figure shown, what is the method of sterilization used?

A) Autoclave
B) High pressure
C) Osmotic pressure
D) Radiation
E) Filtration

Filtration

145
card image

In the photo shown, it can be concluded that the quaternary ammonium compound (Quat) was most effective against:

A) It is impossible to determine from the photo
B) Staphylococcus aureus
C) They are all equally affected by the quat
D) Escherichia coli
E) Pseudomonas aeruginosa

Staphylococcus aureus

146
card image

All of the following conclusions are correct regarding the photos of the disk-diffusion assay EXCEPT:

A) Gram-negative bacteria are the most sensitive
to the chemicals.
B) Only one of the four chemicals affected
pseudomonas.
C) Gram-positive bacteria are the most sensitive
to the chemicals.
D) Hexachlorophene was effective against gram-
positive bacteria only.
E) Chlorine was effective against all the test
bacteria.

Gram-negative bacteria are the most sensitive to the chemicals.

147
card image

All of the following conclusions are correct regarding the graph shown EXCEPT:

A) The tincture of iodine was the most effective
chemical agent.
B) Soap and water were shown to be the least
effective chemical agent.
C) By 2 minutes, 70% ethanol and 30% water had
killed 90% of the bacteria.
D) Aqueous Zephiran is more effective than the
tincture of Zephiran.

Aqueous Zephiran is more effective than the tincture of Zephiran.

148
card image

The clear zones around the coins on the plate in the photo are due which phenomenon?

A) The triclosan in the coins.
B) The oligodynamic action of the metals in the
coins.
C) The halogens present in the coins.
D) The surfactants in the coins.
E) The quaternary ammonium compounds in the coins.

The oligodynamic action of the metals in the coins.

149
card image

Which chemical shown is a common ingredient in antibacterial soaps and at least one toothpaste?

A) Benzalkonium chloriede (Zephiran)
B) Triclosan
C) Hexachlorophene
D) Phenol

Triclosan

150

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 seven days the dry weight of fungi on the treated apples is 5 mg and 10 mg on the untreated apples. You conclude from these results that:

A) the compound is toxic to humans.
B) the compound is fungistatic.
C) apple spoilage is caused by fungi.
D) the compound kills fungi.

The compound is fungistatic.

151

You contaminate kitchen counters with Salmonella enterica in chicken blood and expose it to a variety of treatments to study the survival of the bacteria on kitchen surfaces. The following DRT values were obtained: 2.0 min. at 52° C; 3.7 min. at pH 2.6; 13.3 min. with 10mM hydrogen peroxide; and >35 days without treatment. Which treatment is most effective against S. enterica?

A) acid
B) heat
C) a, b, and c are equivalent treatments
D) hydrogen peroxide

Heat.

152

The best definition of sterilization is the:

A) removal of all microorganisms.
B) elimination of bacteria.
C) removal of unwanted microorganisms.
D) removal of Clostridium botulinum endospores.

Removal of all microorganisms.

153

What is the difference between a disinfectant and an antiseptic?

A) Disinfectants kill some microorganisms;
antiseptics kill all microorganisms.
B) Disinfectants kill microorganisms; antiseptics
inhibit microbial growth.
C) Disinfectants are used on environmental
surfaces; antiseptics are used on living
tissue.
D) Disinfectants remove all microorganisms;
antiseptics remove some microorganisms.

Disinfectants are used on environmental surfaces; antiseptics are used on living tissue.

154

Which of the following treatments achieves sterilization?

A) pasteurization
B) boiling
C) autoclaving
D) commercial sterilization

Autoclaving.

155

Which one of the following is not an antiseptic?

A) iodine
B) alcohol
C) bispenol
D) soap

Soap.

156

Which one of the following kills cells by damaging DNA?

A) deep-freezing
B) ultraviolet light
C) alcohol
D) pasteurization

Ultraviolet light.

157

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

A) bisphenol
B) iodine
C) chlorine
D) phenolic

Chlorine.

158

Which one of the following is not an antiseptic?

A) mercurochrome
B) iodine
C) hydrogen peroxide
D) alcohol

Hydrogen peroxide.

159

Which one of the following methods is bactericidal?

A) deep-freezing
B) filtration
C) lyophilization
D) none of these are bactericidal

None of these are bactericidal.

160

Which one of the following is effective against bacterial endospores?

A) biguanide
B) hexachlorophene
C) chlorine bleach
D) mercury

Chlorine bleach.

161

Which one of the following concentrations of ethyl alcohol is the most effective disinfectant?

A) 50%
B) 25%
C) 75%
D) 100%

75%

162

Four compounds are tested for their disinfectant activity. Compound A kills pseudomonads, mycobacteria, endospores, lipophilic viruses, and hydrophilic viruses. Compound B kills pseudomonads, mycobacteria, and lipophilic viruses. Compound C kills pseudomonads and lipophilic viruses. Compound D does not kill any of the test organisms. Which compound is most likely a soap?

A) Compound C
B) Compound B
C) Compound A
D) Compound D

Compound D.

163

Which of the following is not an oxidizing agent?

A) chlorine
B) hydrogen peroxide
C) triclosan
D) ozone

Triclosan.

164

Which one of the following is most useful for disinfecting medical instruments?

A) iodine
B) mercurochrome
C) alcohols
D) glutaraldehyde

Glutaraldehyde.

165

Which one of the following is generally the easiest to kill?

A) lipophilic viruses
B) hydrophilic viruses
C) Pseudomonas
D) endospores

Lipophilic viruses.

166

The use-dilution values for three disinfectants tested under the same conditions are: Disinfectant X- 1:10; Disinfectant Y-1:100; Disinfectant Z- 1:1,000. If the disinfectants are non-toxic and designed for the same purpose, which would you select?

A) They are equivalent treatments; it doesn't
matter.
B) Y
C) X
D) Z

Z.

167

The disk-diffusion test is used to test disinfectants against Staphylococcus aureus. For Disinfectant A, a 1:10 dilution gives a 25 mm zone of inhibition; 1:100 has a 15 mm zone of inhibition; and 1:1000 gives a 0 mm zone of inhibition. For Disinfectant B, a 1:10 dilution gives a 50 mm zone of inhibition; 1:100 has a 25 mm zone of inhibition; and 1:1000 gives a 10 mm zone of inhibition. Which disinfectant is most effective?

A) they are equally effective
B) cannot tell from the information given
C) B
D) A

B.

168

The disk-diffusion test is used to test disinfectants against Staphylococcus aureus. For Disinfectant A, a 1:10 dilution gives a 25 mm zone of inhibition; 1:100 has a 15 mm zone of inhibition; and 1:1000 gives a 0 mm zone of inhibition. For Disinfectant B, 1:10 dilution gives a 50 mm zone of inhibition; 1:100 has a 25 mm zone of inhibition; and 1:1000 gives a 10 mm zone of inhibition. Which disinfectant is bactericidal?

A) they are equally effective
B) A
C) cannot tell from the information given
D) B

Cannot tell from the information given.

169

You inoculate a nutrient agar plate with your fingers after washing your hands with water. Then you wash your hands with bar soap, rinse, and inoculate another nutrient agar plate. You repeat the handwashing with liquid soap and inoculate a third nutrient agar plate. The bar soap and liquid soap have the same chemical formulas. After incubating the plates, you record the amount of bacterial growth on a scale of - (no growth) to 3+ (maximum growth). Your results are: Water alone, +; Bar soap and water, 3+; Liquid soap and water, +. From these data, you can conclude that:

A) bacteria persist on bar soap.
B) soap kills bacteria.
C) liquid soap kills bacteria.
D) water kills bacteria.

Bacteria persist on bar soap.


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