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Microbiology > 3 - Sterilization and Disinfection > Flashcards

3 - Sterilization and Disinfection Flashcards

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1
Q

TOTAL inactivation of ALL forms of microbial life. Renders pathogen the inability to reproduce.

A

Sterilization

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2
Q

Most resistant to sterilization

A

Spores

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3
Q

Least resistant to sterilization

A

Viruses

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4
Q

Destruction of microorganism capable of causing infection by means of a germicidal agent

A

Disinfection

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5
Q

Reduction in the number of pathogens to a level that is unlikely to cause infection

A

Disinfection

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6
Q

Disinfection is done on?

A

Inanimate objects and surfaces

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7
Q

Are disinfectants sporicidal or sporostatic?

A

Sporostatic

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8
Q

A germicidal agent that destroys or kills bacteria by an irreversible process.

A

Bactericidal

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9
Q

A germicidal agent that reversibly inhibits the growth of bacteria.

A

Bacteriostatic

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10
Q

TOPICAL chemical agent applied to a body surface or living tissue that kills or inhibits the growth of pathogenic microorganisms

A

Antiseptic

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11
Q

Use of disinfectant to lower microbial content of inanimate objects/utensils

A

Sanitization

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12
Q

Antiseptic is applied to?

A

Body surfaces

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13
Q

Compare antiseptic and disinfectant: action

A

Antiseptic: Bacteriostatic
Disinfectant: Bacteriocidal

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14
Q

Regarded as drug

A

Antiseptic

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15
Q

Regarded as environmental poison

A

Disinfectant

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16
Q

Used at the lowest concentration that results to desired effect

A

Antiseptic

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17
Q

Used at highest concentration

A

Disinfectant

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18
Q

Lowers microbial counts on eating and drinking utensils to safe public health levels

A

Sanitization

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19
Q

Prevention of multiplication of microorganisms in formulated objects (pharmaceuticals and foods

A

Preservation

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20
Q

Two methods of sterilization

A

Physical and Chemical

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21
Q

Most reliable; universally applicable; simplest method of sterilization

A

Heating

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22
Q

6 mechanisms of thermal injury caused by heating.

A
  1. Single strand breaks
  2. Membrane integrity
  3. Protein denaturation/coagulation
  4. Oxidative damage
  5. Elevated electrolytes
  6. Simulated environment for growth
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23
Q

The sterilization of a bacterial population by heat is a GRADUAL process. True or False?

A

True

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24
Q

How is the kinetics of death of pathogens described in heating?

A

Exponential

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25
Q

Preferred method of heating

A

Use of MOIST heat

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26
Q

Vegetative forms are destroyed in moist heat at ____ in ____ minutes

A

80C in 5-10 minutes

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27
Q

Spores are destroyed in moist heat at ____ in ____ minutes

A

120C in 4 minutes

100C in 5.5 hours

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28
Q

True or false. LOWER temperature = shorter time to kill.

A

False. Higher temperature = shorter time to kill

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29
Q

Moist heat basically kills microorganisms by ______.

A

Protein denaturation

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30
Q

4 forms of Moist Heat sterilization

A
  1. Steam under pressure (autoclaving)
  2. Boiling
  3. Fractional sterilization/Tyndallization
  4. Pasteurization
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31
Q

Used for sterilizing materials that would be damaged by autoclaving

A

Fractional sterilization/Tyndallization

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32
Q

Kills ALL VEGETATIVE forms of pathogenic organisms at 80-100 °C for 10-30 minutes but NOT bacterial ENDOSPORES

A

Boiling

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33
Q

Boiling kills all vegetative forms of pathogens at ____ C for ___ minutes.

A

80-100C for 10-30 minutes

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34
Q

Heating 80-100 °C x 30 minutes for 3 consecutive days with incubation periods in between

A

Fractional sterilization/Tyndallization

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35
Q

Most efficient method of moist heat sterilization

A

Steam under pressure (autoclaving)

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36
Q

Allows application of moist heat above the normal atmospheric boiling point of water

A

Steam under pressure (autoclaving)

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37
Q

Temp. at which autoclaving is done at 15 psi for 15-90 minutes

A

121C

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38
Q

Temp. at which autoclaving is done at 27 psi for 4-20 minutes

A

132C

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39
Q

Used to sterilize surgical bandages, instruments, media

and to decontaminate reusable supplies and equipment

A

Steam under pressure (autoclaving)

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40
Q

One disadvantage of steam under pressure

A

Damages heat-sensitive materials

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41
Q

This method of moist heat sterilizations is cumbersome/impractical for everyday use.

A

Boiling

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42
Q

One advantage of boiling

A

Minimal equipment is used

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43
Q

Used to sterilize HEAT-SENSITIVE MATERIALS, BACTERIOLOGIC MEDIA, SOLUTIONS OF CHEMICAL

A

Fractional sterilization or Tyndallization

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44
Q

Temp of pasteurization

A

Below boiling point (77C)

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45
Q

Used to sterilize milk and dairy products, food and beverages

A

Pasteurization

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46
Q

True or False. Relatively heat-resistant bacteria survive pastuerization but are unlikely to cause disease.

A

True

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47
Q

True or False. Pasteurization can be ised on heat sensitive liquids and medical devices.

A

True.

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48
Q

An unreliable sporicidal in moist heat sterilization

A

Pasteurization

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49
Q

This method of heat sterilization requires higher temperature and longer exposure to heat

A

Dry heat

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50
Q

Where does DRY HEATING depend upon to be effective?

A

Effectiveness of dry heat depends on penetration of heat through the material

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51
Q

How does DRY HEAT kill all microrganisms?

A

Through its OXIDATION effects

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52
Q

3 forms of Dry Heat Sterilization

A

Hot air oven
Red heat flame
Incineration

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53
Q

Most widely used Dry Heat method

A

Hot air oven

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54
Q

Temp of dry heat

A

160-180C for 2-4 hrs

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55
Q

Dry Heat method ised for anhydrous materials, oils and powder, lab glassware and instruments

A

Hot air oven

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56
Q

Sterilization via oxidation to ashes/burning

A

Red heat flame

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57
Q

Used in sterilization of inoculating loops, needles

A

Red Heat Flame

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58
Q

Sterilization via oxidation to ashes/burning at temp >1000C

A

Incineration

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59
Q

Sterilization technique in decontamination of waste items prior to disposal (hospital wastes)

A

Incineration

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60
Q

Penetrates water insoluble materials

A

Hot air oven

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61
Q

Disadvantages include slow diffusion and not suitable to reusable plastics

A

Hot air oven

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62
Q

Less corrosive to metals and sharp instruments

A

Hot air oven

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63
Q

Rapid heating method

A

Red heat flame

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64
Q

Initial contact with flame produces a viable aerosol

A

Red heat flame

65
Q

May lead to accidental fire

A

Red heat flame

66
Q

Reduces volume of waste by 95%

A

Incineration

67
Q

One disadvantage is this requires transport of infectious waste

A

Incineration

68
Q

Aside from pasteurization, this sterilization technique is not reliably sporicidal and is time consuming too

A

Fractional sterilization/tyndallization

69
Q

One disdavantage is shielding dirt must first be removed

A

Autoclave

70
Q

Most dependable heat sterilization technique

A

Autoclave

71
Q

Another physical method of sterilization in which it deprives bacteria of water, thus inhibiting its growth and reproduction

A

Dessication

72
Q

Resistant to drying or dessication

A

Bacterial spores

73
Q

Used in preservation of foods

A

Dessication

74
Q

Inhibiting bacterial metabolism and growth by exposing it to very low temperatures

A

Freezing

75
Q

True or False. Freezing destroys microorganisms

A

False

76
Q

In which bacteria is freezing ineffective

A

Psychrophiles/cryophiles

77
Q

When is freezing used?

A

Preservation of foods

78
Q

Similar to freezing but is done rapidly. Samples are stored in sealed ampules. Has longer shelf life.

A

Lyophilization

79
Q

Used in: laboratories, pharmaceuticals,cryogenic

A

Lyophilization

80
Q

2 forms of radiation

A

UVL

Ionizing Radiation

81
Q

Most effective bactericidal

A

Ultraviolet Light

82
Q

Wave length of UVL and optimum emitted by UV lamps

A

240-280nm; optimum 260nm

83
Q

Germicidal and reduces the number of microbes on exposed surfaces and in air

A

UVL

84
Q

Used normally in disinfecting air

A

UVL

85
Q

3 disadvantages of UVL

A

Poor penetrating power
Hazardous to skin and eyes
Damages DNA

86
Q

Has greater penetrating ability than UVL because it has shorter wavelength and carries MORE energy.

A

Ionizing Radiation

87
Q

One disadvantage of ionizing radiation

A

Potentially hazardous to human cells

88
Q

Mechanical sieving or physical separation of microorganism from the fluid

A

Filtration

89
Q

What is used in filtration

A

Cellulose ester membranes

90
Q

Size that allows passage through filtration

A

0.22 um

91
Q

Physical sterilization that makes use of salt addition

A

Osmotic pressure

92
Q

Method for vaccine preparation

A

Lyophilization

93
Q

Examples of organisms that can pass through filter paper

A

Viruses, chlamydia, rickettsia, mycoplasma

94
Q

Produces ions and other reactive molecular species from molecules with which the radiation particles collide

A

Ionizing Radiation

95
Q

Give example of sterilization by osmotic pressure

A

Used in dried fish

96
Q

Disrupts cells via bacterial cavitation causing disintegration and denaturation

A

Use of ultrasonic vibrations

97
Q

Formation of partial vacuum in a liquid medium

A

Bacterial cavitation

98
Q

Used for breaking open tissue cells and treating renal or gall stones

A

Ultrasonic vibration

99
Q

5 modes of actions of sterilants or disinfectants

A
  1. Damage to DNA
  2. Protein denaturation
  3. Cell membrane or wall disruption
  4. Removal of free sulfhydryl groups
  5. Chemical antagonism
100
Q

3 chemicals that damage the cell membrane

A
  1. Surface active disinfectants
  2. Phenolic compounds
  3. Alcohol
101
Q

Alters the energy relationships at interfaces causing reduction of surface tension

A

Surface Active Disinfectants or Surfactants

102
Q

How does a surface active disinfectant denature microbial enzymes and proteins?

A

By disrupting the hydrogen and sulfide bonds causing a block in metabolism

103
Q

Distorts cellular membrane and loss of membrane permeability causing leakage of N and P containing compounds

A

Cationic Compounds - Quaternary ammonium compounds

104
Q

Surface Active Disinfectant most effective at alkaline pH

A

Cationic Compounds - Quaternary ammonium compounds

105
Q

Are Cationic Compounds - Quaternary ammonium compounds sporicidal or sporostatic?

A

Sporostatic - inhibits the growth but not the actual germination process

106
Q

Mycobacteristatic

A

Cationic Compounds - Quaternary ammonium compounds

107
Q

Have an effect on enveloped but NOT LIPID-enveloped viruses

A

Cationic Compounds - Quaternary ammonium compounds

108
Q

Examples of Cationic Compounds - Quaternary ammonium compounds

A

Zephiran

Benzalkonium chloride

109
Q

Disrupts lipoprotein framework of the CM and most effective at acid pH

A

Anionic compunds - Soaps and detergents

110
Q

Causes leakage of cell contents and IRREVERSIBLE INACTIVATION of membrane bound oxidases and dehydrogenases

A

Phenolic Compounds

111
Q

Kill bacteria, most fungi & some viruses but are ineffective against endospores

A

Phenolic Compounds

112
Q

Rapid, broad-spectrum antimicrobial activity against vegetative bacteria, viruses, and fungi but are not sporicidal

A

Alcohols

113
Q

Activity is optimal when they are diluted to a concentration of 60-90% with water

A

Alcohols

114
Q

Most effective alcohol at 50 - 70% and is used as a skin disinfectant

A

Ethyl aclohol

115
Q

Alcohol that cannot destroy spores at normal temp

A

Ethyl acohol

116
Q

Less volatile alcohol, has greater bactericidal activity and toxic effect

A

Isopropyl alcohol

117
Q

2 chemicals for protein denaturation

A
  1. Acids and Alkalis

2. Alcohol and acetone

118
Q

Exert their action through free H and OH ions and alter the pH of the organism’s environment

A

Acids and alkalis

119
Q

4 chemicals for for functional group, proteins and Nucleic Acid Modification

A
  1. Heavy metals
  2. Oxidizing agents
  3. Dyes
  4. Alkylating agents
120
Q

How do heavy metals poison enzyme activity?

A

By forming mercaptides with the SH groups of cysteine residues

121
Q

Not reliable heavy metal disinfectants

A

Mercurials: merthiolate and mercurochrome antiseptics

122
Q

Prevents gonococcal ophthalmia

A

Silver nitrate 1%

123
Q

Used to combat fungal diseases of plants and is also a common algicide

A

Copper sulfate

124
Q

Inactivate enzymes converting functional SH groups to oxidized S-S for stronger agents; also attack amino groups, indole groups and phenolic hydroxyl groups of tyrosine

A

Oxidizing agents

125
Q

Oxidizing agent that is bactericidal; effective against sporulating org, Mycobacterium tuberculosis

A

Halogens

126
Q

Oxidizing agents that destroy the cellular activity of proteins; examples are chlorine and iodine

A

Halogens

127
Q

BEST antiseptic because it kills spores, viruses, fungi, some endospores; usually dissolved in an alcohol solution to produce a tincture

A

Iodine

128
Q

Combination of iodine and an anionic detergent that reduces surface tension and slowly releases the iodine

A

Iodophores

129
Q

Complexes of iodine and a solubilizing agent or carrier

A

Iodophores

130
Q

Example is povidone-iodine

A

Iodophore

131
Q

Liberates free chlorine and is used as WATER DISINFECTANT

A

Chlorine

132
Q

Sanitizes dairy and food processing equipment household and hospitals

A

Hypochlorite

133
Q

Active agent in household bleach

A

Sodium hypochlorite

134
Q

Weak antiseptic; has broad spectrum of activity however, it should be applied in higher concentrations of about 10-30% which is already very toxic to humans

A

Hydrogen peroxide

135
Q

Once used in cleaning wounds, disinfection of surgical devices and soft plastic contact lenses

A

Hydrogen peroxide (H2O2)

136
Q

Limited in treatment of dermatologic lesions; stain bacteria

A

Dyes

137
Q

o Brilliant green
o Malachite green
o Crystal violet

A

Triphenylmethane

138
Q

o Wound antiseptics

o Retain antimicrobial activity in the presence of serum

A

Acridines

139
Q

An alkylating agent that preserves specimens and used in preparation of vaccine ( whole-killed and toxoid)

A

Formaldehyde (formalin)

140
Q

Kill M. tuberculosis in sputum and fungus in athlete’s foot; destroys all org including spores

A

Formaldehyde (formalin)

141
Q

Sporicidal, virucidal and bactericidal; 10x more effective than formaldehyde and less toxic

A

Glutaraldehyde

142
Q

Cold sterilant for surgical instruments e.g. Cidex

A

Glutaraldehyde

143
Q

Gas sterilization of 50-1200 mg/L x 1-12 hrs

A

Ethylene oxide

144
Q

Penetrates packaging material (polyethylenes tubes, electronic and medical equipment, biological and drugs)

A

Ethylene oxide

145
Q

Sterilizes heart and lung machines

A

Ethylene oxide

146
Q

potentially mutagenic and carcinogenic in humans (vapors are toxic to skin, eyes and mucous membranes)

A

Ethylene oxide

147
Q

6 factors affecting disinfectant potency

A
  1. Concentration of chemical agent
  2. Time
  3. Temperature
  4. pH
  5. Nature of medium
  6. Nature of agent
148
Q

Higher concentration of chemical agent means the disinfectants is bacteriocidal or bacteriostatic?

A

Bacteriocidal

149
Q

True or False Increase in time of contact = increase killing of morgs

A

True

150
Q

Effect of excessive heat

A

Protein denaturation

151
Q

True or False.The H+ ion conc. influences both the organism and chemical agent

A

True

152
Q

Determines the degree of ionization of the chemical agent

A

pH

153
Q

presence of extraneous materials increases the efficiency of chemical agent. true or false.

A

False. Increases

154
Q

Standard reference material based on tube dilution procedure determine the ratio of the highest dilution that will kill the org within a specified time to the greatest dilution of phenol showing the same result

A

Phenol coefficient test

155
Q

2 organisms used in the phenol coefficient test

A
  1. Salmonella typhi

2. Staphylococcus aureus

156
Q

Another method of evaluating chemical disinfectant efficacy that utilizes an agar and a paper

A

Filter Paper method

157
Q

Most efficacious disinfectant that completely kills microbes at lowest dilutions

A

Use-dilution test

158
Q

Organism air dried onto a stainless steel surface&raquo_space; exposed to disinfectant : following sterile water rinsing the entire surface placed in broth&raquo_space; successful disinfection&raquo_space; no bacterial growth in the broth

A

Use-dilution test

Microbiology (7 decks)

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