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disinfectants Flashcards

1
Q

what is sterilisation

A

process that destroys or eliminates all forms of microbial life and is carried out in healthcare facilities by physical or chemical methods, sporicidal

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2
Q

what are chemical sterilants

A

chemicals that are used to destroy all forms of microbial life

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3
Q

can chemical sterilants kill spores

A

yes with prolonged exposure

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4
Q

what is disinfection

A

process that eliminates many or all pathogenic microorganisms, except bacterial spores on inanimate objects, non sporicidal

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5
Q

what is high level disinfection

A

chemical sterilants that are at similar conc that can kill spores over a prolonged exposure time but with shorter exposure periods can kill all microorganisms except large numbers of bacterial spores

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6
Q

what is low level disinfection

A

kills most vegetative bacteria, some fungi, some viruses in a practical amount of time

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7
Q

what is cleaning

A

cleaning is the removal of visible soil from objects or surfaces and is normally accomplished manually or mechanically using water with detergent or enzymatic products

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8
Q

what is decontamination

A

removal of pathogenic microorganisms from objects so they are safe to handle, use or discard

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9
Q

what processes constitutes as decontamination

A

disinfection, sterilisation, antisepsis

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10
Q

what is the difference between antiseptics and disinfectants

A

antiseptics are germicides applied only to skin while disinfectants are antimicrobials only applied to inanimate objects as it can injure skin and other tissues

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11
Q

what constitutes as biocides

A

antiseptics and disinfectants

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12
Q

what are the biocides used for

A

to fight microorganisms on human skin and on nonliving surfaces

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13
Q

what is the difference between biocides and abx

A

biocides have broader spectrum of activity than abx and may have multiple targets

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14
Q

what kind of activity does biocides have

A

-static: inhibit growth, -cidal: kill target microorganism

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15
Q

what are the different types of microorganisms

A

bacteria, fungi, spores, virus, prions

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16
Q

what defines as a bacteria

A

free living organisms often consisting of one biological cell

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17
Q

what defines as a fungi

A

eukaryotic organisms (contains nucleus)

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18
Q

what defines as a spore

A

unit of sexual or asexual reproduction adapted for dispersal

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19
Q

what defines as a virus

A

sub microscopic infectious microorganisms that replicate inside biological cell

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20
Q

what defines as a prion

A

misfolded proteins that may transmit their misfolded shape onto normal variants

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21
Q

what is a bacterial envelope

A

polysaccharide layer that lies outside the cell envelope

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22
Q

what is the difference between gram pos and gram neg

A

gram pos has no outer membrane while gram neg has a thin peptidoglycan layer with outer membrane

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23
Q

what is the difference between nonenveloped and enveloped virus

A

nonenveloped virus lacks lipid membrane while an enveloped virus has phospholipids and proteins with some viral glycoprotein

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24
Q

what is a capsid

A

oligomeric protomers between genome and envelop

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25
Q

what is the role of the capsid

A

acts as a protein shell of a virus, enclosing its genetic material

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26
Q

what is the activity of germicides dependent on

A

activity of germicides against microorganisms depends on intrinsic qualities of the organism, chemical and external physical environment

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27
Q

what are the factors that affect the efficacy of disinfection and sterilisation

A

number of microbes, innate resistance of organisms, conc and potency of disinfectants, chemical and physical factors, organic and inorganic matter, duration of exposure, biofilm

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28
Q

how does number of microbes affect efficacy of disinfection and sterilisation

A

more number of microbes = more killing required

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29
Q

what is the factor that determines the innate resistance of microorganisms

A

composition of outer layer

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30
Q

what are the main three types of microorganisms that can possess innate resistance and why

A

spores, mycobacteria and gram neg bacteria as they possess an outer layer

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31
Q

what are the different outer layers that spores, mycobacteria and gram neg bacteria have

A

spores have spore coat and cortex that act as barriers, mycobacteria has waxy cell wall that prevents entry and gram neg bacteria possess outer membrane that acts as barrier

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32
Q

how does conc and potency of disinfectants affect efficacy of disinfection and sterilisation

A

more conc and potent = greater efficacy and shorter time required but not linear r/s

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33
Q

what are the physical and chemical factors to consider when determining efficacy of disinfection and sterilisation

A

temp, pH, relative humidity, water hardness

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34
Q

hows does each physical and chemical factor affect efficacy of disinfection and sterilisation

A

i) temp incr = disinfection incr but may lead to degradation
ii) pH incr can incr or decr by antimicrobial activity by altering disinfectant molecule or cell surface (to make action more effective by destroying outer layer)
iii) relative humidity is single most important factor influencing activity of gaseous disinfectants as water may help disinfectant with direction and help transmit to microorganism to be more effective
iv) water hardness reduces rate of kill as divalent cations in hard water can interact with disinfectant to form insoluble precipitates

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35
Q

which chemical disinfectant has activity increased when pH increases

A

glutaraldehyde, QAC

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36
Q

which chemical disinfectant has activity decreased when pH increases

A

phenols, hypochlorites, iodine

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37
Q

what are examples of gaseous disinfectants that would be affected by relative humidity

A

ethanol, chlorine dioxide, formaldehyde

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38
Q

how does organic and inorganic matter affect efficacy of disinfection and sterilisation

A

organic material can interfere with activity through chemical reaction with germicide such that there is reduction in potency or full inactivation or through protection by occlusion in salt crystals (precipitation or inclusion so there is no direct contact between microorganism and disinfectant)

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39
Q

what are examples of organic material

A

blood, serum, pus, fecal

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40
Q

how does duration of exposure affect efficacy of disinfection and sterilisation

A

longer duration of exposure = more killing done

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41
Q

what are biofilms

A

microbial communities that are tightly attached to surfaces and cannot be easily removed

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42
Q

what are the mechanisms in which microbes within biofilms can be resistant to disinfectants by

A

layers of old biofilms, genotypic variation (like of the membrane), neutralizing enzymes, physiologic conditions

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43
Q

what are chemical disinfectants

A

disinfectants that are chemical agents applied to non living objects in order to destroy bacteria, viruses, fungi or mould with active ingredients that kill pathogens usually by disrupting or damaging their cells, aided by other ingredients like emollient or surfactant

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44
Q

what are examples of chemical disinfectants

A

alcohols, ammonia, aldehyde, biguanides, chlorine and chlorine compounds, iodine and iodophors, peroxygens, accelerated h2o2, peracetic acid, phenols, chloroxylenol, diamidines, Ag compounds, mercuric chloride, QAC

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45
Q

what is alcohol’s spectrum of activity

A

against vegetative bacteria, viruses and fungi, not sporicidal

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46
Q

what is the optimal conc of alcohol

A

60-90%

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47
Q

what type of activity does alcohol have

A

bactericidal but can be bacteriostatic

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48
Q

how can alcohol be bacteriostatic

A

by inhibition of production of metabolites essential for cell division

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49
Q

what are the uses of alcohol

A

used for hard surface disinfection and skin antisepsis

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50
Q

what is the mechanism of action of alcohol

A

denatures proteins and mechanism increased by water

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51
Q

what is the difference in efficacy between isopropyl and ethyl alcohol

A

isopropyl alcohol has greater lipophilic properties than ethyl alcohol thus its more efficacious against non enveloped

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52
Q

what are the uses of ammonia

A

general purpose cleaner for many surfaces

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53
Q

what is the mechanism of action of ammonia

A

works by saponifying lipids within the envelopes of the microorganism by making a salt complex which forms a precipitation

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54
Q

what happens when ammonia is in aq solution

A

ammonia deprotonates a small fraction of water to give ammonia and hydroxide with pH 11-12

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55
Q

what are the disadvantages of ammonia

A

irritant for eyes and gastric system, releases toxic chloramine if mixed with bleach

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56
Q

what is chloramine

A

a derivative of ammonia and organic amines where one or more NH bonds is replaced by NCl bonds

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57
Q

what are the uses of chloramine

A

disinfectant used to treat drinking water, mono most commonly used as it does not break down in water pipes easily so it provides long lasting protection

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58
Q

what is tri chloramine associated with

A

pool water

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59
Q

what type of activity does aldehyde have

A

biocidal

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60
Q

what is the mechanism of action of aldehyde

A

alkylation of sulfhydryl, hydroxyl, carboxyl and amino groups of microorganism alters RNA, DNA and protein synthesis

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61
Q

what are the uses of aldehyde

A

antisepsis, disinfection, preservation

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62
Q

what are the disadvantages of aldehyde

A

toxicity and odor

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63
Q

how does aldehyde interact with bacterial spores, mycobacteria, nonsporulating bacteria, fungi and viruses

A

bacterial spores: low conc inhibit germination, high conc sporicidal due to strong interaction with outer cell layers

mycobacteria: interaction with cell wall

nonsporulating bacteria: affect gram pos and gram neg by cross linking with amino groups in protein and inhibiting transport processes into cell

fungi: possible interaction with chitin in fungal cell wall

viruses: protein DNA cross links and capsid changes

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64
Q

what is an example of an aldehyde used

A

ortho-phthaldehyde (OPA)

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65
Q

what are the properties of OPA

A

clear pale blue liquid with pH 7.5, lipophilicity assist uptake by outer layer of mycobacteria and gram neg bacteria, excellent stability over a wide range of pH 3-9, not a known irritant to eye and nasal passage, no perceptible odor, excellent material compatibility, stains proteins grey including unprotected skin so handle with caution

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66
Q

what is the mechanism of action of OPA

A

cross linking agent that link irreversible with bacteria DNA to block and kill, block spore germination by interacting with protein, AA and microorganisms

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67
Q

what are some examples of biguanides

A

chlorhexidine, alexidine

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68
Q

what type of activity does chlorhexidine have

A

bactericidal

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69
Q

what are the uses of chlorhexidine

A

disinfectant and preservative

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70
Q

what type of salt is chlorhexidine in eyedrops as a preservative

A

0.01% of either acetate or gluconate salt

71
Q

at what conc can chlorhexidine gluconate salt be used as contact lens disinfectant

A

0.002-0.006%

72
Q

at what conc can chlorhexidine be used as skin disinfectant

A

0.5% in 70% ethanol

73
Q

at what conc can chlorhexidine be used as a surgical scrub disinfectant

A

4% with detergents

74
Q

what products are chlorhexidine found in

A

contact lens solution, surgical scrubs, skin disinfectant, topical antiseptic cream, mouthwash, dental gels, catheter sterilisation, bladder irrigation, constituents of medical dressings, dusting powders, sprays and creams

75
Q

what types of properties does chlorhexidine have

A

activity is pH dependent, activity greatly reduced in organic matter, cationic thus incompatible with anionic materials and soaps (compatible with cationic and nonionic surfactants)

76
Q

what happens if high conc of surfactants used with chlorhexidine

A

can cause micellar binding thus reducing activity

77
Q

what is the mechanism of action of chlorhexidine

A

damages outer cell membrane and crosses by passive diffusion, followed by attacking bacterial cytoplasmic through coagulation or gelling

78
Q

what is the difference in structure between alexidine and chlorhexidine

A

alexidine possesses ethylhexyl end groups

79
Q

what is the mechanism of action of alexidine

A

apoptosis via destruction of bacterial cell membrane, faster onset of bactericidal activity and produces a significantly faster alteration in bactericidal permeability, produces lipid phase separation

80
Q

what are examples of chlorine and chlorine compounds

A

hypochlorites, chloramine, sodium dichloroisocyanurate

81
Q

what are the forms of hypochlorite

A

liquid form as sodium hypochlorite, solid form as calcium hypochlorite

82
Q

what is the activity of hypochlorite attributed to

A

undissociated hypochlorous acid (HOCl)

83
Q

what is the dissociation of hypochlorous acid into hypochlorite ion affected by

A

dissociation of HOCl into OCl- affected by pH

84
Q

what happens to dissociation of hypochlorous acid into hypochlorite ion if pH increases

A

pH increases causes more dissociation into OCl- which decreases efficacy

85
Q

what are the properties of hypochlorites

A

do not leave toxic residues and low incidence of serious toxicity, unaffected by water hardness, inexpensive and fast acting, remove dried or fixed organisms and biofilms from surfaces

86
Q

what are the mechanisms of hypochlorites

A

oxidation of sulfyhydryl enzymes and AA, ring chlorination of AA, inhibition of protein synthesis, DNA disruption, loss of intracellular contents

87
Q

what are the disadvantages of hypochlorites

A

ocular irritation, burns mouth/throat/stomach, corrosiveness to metals in high conc, inactivation by organic matter, release of toxic chlorine gas

88
Q

what is the advantage of chloramines over hypochlorites

A

more prolonged bactericidal effect as retains chlorine longer

89
Q

what is the advantage of sodium dichloroisocyanurate over hypochlorites

A

more prolonged bactericidal effect as retains chlorine longer

90
Q

what is the composition of sodium dichloroisocyanurate

A

50% of total available chlorine is free as HOCl and OCl- while remainder is combined to form mono/di-chloroisocyanurate

91
Q

what are the uses of iodine

A

antiseptics on skin or tissue

92
Q

what are the uses of iodine compounds

A

disinfectant and antiseptics

93
Q

what is the mechanism of action of iodine

A

iodine can penetrate through cell wall of microorganisms and disrupt protein and nucleic acid structure and synthesis

94
Q

what is the composition of iodophor

A

iodine and a solubilising agent

95
Q

what is the mechanism of action of iodophor

A

since iodophor is iodine and a solubilising agent, the resulting complex has a sustained release reservoir or iodine and releases small amounts of free iodine in aq solution -> free iodine contributes to bactericidal activity

96
Q

what effect does dilution of iodophor have

A

more rapid action due to increased release of free iodine

97
Q

what is the benefit of slow release of iodine in iodine compounds

A

keep conc minimum for substance to be effective for longer (same as chlorine compounds)

98
Q

what are examples of peroxygens

A

h2o2, accelerated h2o2, peracetic acid

99
Q

what are the uses of h2o2

A

disinfection, sterilisation, antisepsis

100
Q

what are the properties of h2o2

A

clear colourless liquid available in conc 3-90% (commonly 20%), most contain stabilisers like sodium citrate or malonate to prevent decomposition, presence of catalase or other peroxidases can increase tolerance in presence of lower conc, greater activity against gram pos than gram neg

101
Q

what is the mechanism of action of h2o2

A

act as an oxidant by producing hydroxyl free radicals which induces oxidation and attacks essential cell components including lipids, proteins and DNA, and disrupts outer cell membrane and lead to cell death

102
Q

what is the mechanism of resistance to h2o2

A

development of specific enzymes that inactivates some of the radicals formed so less act on cell and thus less effective (more for biofilms)

103
Q

what is the conc required for h2o2 to have sporicidal activity

A

10-30% and longer contact time

104
Q

what is the disadvantage of h2o2

A

can be irritant at high conc if used as antiseptic

105
Q

what is the difference between h2o2 and accelerated h2o2

A

enhanced antimicrobial efficacy from surfactant, organic acid and emulsifier

106
Q

what are the surfactants that can be used for accelerated h2o2

A

alkali metal and ammonium salts or alkyl sulfate

107
Q

what is the benefit of having a surfactant to make accelerated h2o2

A

makes it more effective against outer layer of cell and can penetrate more easily, acts on DNA as well

108
Q

what is the benefit of having organic acid to make accelerated h2o2

A

chelating agent that forms complexes with salts which can activate or inactivate activity of radical

109
Q

what are organic acids that can be used for accelerated h2o2

A

phosphoric acid or phosphonate

110
Q

what are the emulsifiers that can be used for accelerated h2o2

A

salt of an alkylated diphenyl oxide

111
Q

what is the benefit of having emulsifiers to make accelerated h2o2

A

size dispersion of product increases stability

112
Q

what are the properties of accelerated h2o2

A

relatively short half life due to decomposition

113
Q

what are the disadvantages of accelerated h2o2

A

irritant for eyes

114
Q

what is the advantage of peracetic acid

A

more potent than h2o2

115
Q

at what conc does peracetic acid have activity

A

0.3%

116
Q

what is the mechanism of action of peracetic acid

A
117
Q

what are the advantages of peracetic acid

A

decomposes into safe byproducts like acetic acid and oxygen, free from decomposition by peroxidases unlike h2o2, active in presence of organic load, generally safe and can be used at low conc and low temp, mild odor

118
Q

what is peracetic acid commonly used for

A

low temp liquid sterilant for medical devices and environmental surfaces

119
Q

what are the uses of phenol

A

disinfectant, antiseptic, preservative (but less common now)

120
Q

what is the mechanism of action of phenol

A

disrupts outer layer and induces progressive leakage of cell constituents including K+ which is usually the first index of membrane damage as it is difficult to pump it back in to maintain equilibrium

121
Q

what are the uses of chloroxylenol and at what conc

A

antiseptic (0.5%), antimicrobial (0.1-0.8%), disinfectant (2.5-5%)

122
Q

what is the mechanism of action of chloroxylenol

A

disrupts microbial cell wall and inactivates cellular enzymes

123
Q

what is chloroxylenol commonly used with

A

edetic acid

124
Q

what are the common uses of edetic acid

A

chelating agents in food and cosmetics to form water-soluble complexes with alkaline metal ions

125
Q

what is the metal-edetate complex stability dependent on

A

metal ion involved and pH

126
Q

what are the uses of diamidines

A

antiseptic and disinfectants

127
Q

what is the mechanism of action of diamidines

A

inhibits oxygen uptake and leakage of AA

128
Q

what are examples of diamidine

A

isethionate salts of propamidine and dibromomidine

129
Q

what are examples of Ag compounds

A

silver nitrate, silver sulfadiazine

130
Q

what is the mechanism of action of silver nitrate

A

interaction with thiol (sulfydryl -SH) groups in enzymes and proteins

131
Q

what is the composition of silver sulfadiazine and what is its significance

A

silver and sulfazine which are two antibacterial agents

132
Q

what is the difference between silver nitrate and silver sulfadiazine

A

silber sulfadiazine has broader spectrum

133
Q

what is the mechanism of action of silver sulfadiazine

A

induces membrane blebs in susceptible bacteria

134
Q

what are the uses of mercuric chloride (HgCl2)

A

broad range disinfectant

135
Q

what is the mechanism of action of mercuric chloride

A

affect microbial peptide synthesis

136
Q

what is the disadvantage of mercuric chloride

A

highly toxic both acutely and as a cumulative poison, toxic and corrosive, tends to accumulate in kidneys and cause severe corrosive damage which can lead to acute kidney failure

137
Q

what is an example of QAC

A

benzalkonium chloride

138
Q

what is the structure of QAC

A

R1-4 are alkyl or heterocyclic radicles, A- is halide, sulfate or similar radical

139
Q

what are QAC known as

A

cationic detergents

140
Q

what are the uses of QAC

A

preoperative disinfection of unbroken skin, application to mucus membranes, disinfection of noncritical surfaces (floors, furniture and walls)

141
Q

what type of activity does QAC have

A

fungicidal, bactericidal, virucidal against lipophilic viruses, not sporicidal

142
Q

what is the mechanism of action of QAC

A

adsorption and penetration into cell wall -> interact with cytoplasmic membrane followed by membrane degradation -> leakage of intracellular low Mr material -> degradation of protein and nucleic acids -> wall lysis caused by autolytic enzymes at higher conc

143
Q

why cant QAC be used in open wounds

A

can cause autolysis of cells

144
Q

what is benzalkonium chloride often in combination with and why

A

surfactant to disrupt outer layer as main activity is within cell

145
Q

what are the properties of benzalkonium chloride

A

more activity against gram pos than gram neg, minimal against bacterial endospores and acid-fast bacteria, non irritating, non sensitising and well tolerated

146
Q

what is activity of benzalkonium chloride dependent on

A

alkyl composition of homolog mixture (R)

147
Q

what are examples of plant based disinfectant

A

eucalyptus

148
Q

what are the uses of plant based disinfectant

A

against e coli and s. aureus, disinfectant during mining

149
Q

how are plant based disinfectant produced

A

essential oils obtained by steam distillation method

150
Q

what are examples of vapor phase sterilants

A

ethylene oxide, formaldehyde, h2o2, peracetic oxide

151
Q

what are the uses of vapor phase sterilants

A

disinfect/ sterilise heat sensitive medical devices and surgical supplies

152
Q

what is the mechanism of action of ethylene oxide

A

broad spectrum alkylating agents that attack proteins, nucleic acids and other organic compounds, particularly reative with sulfhydryl and other enzyme reactive groups

153
Q

what is the mechanism of action of formaldehyde

A

broad spectrum alkylating agents that attacks proteins, nucleic acids and other organic compounds, particularly reactive with sulfhydryl and other enzyme reactive groups

154
Q

what is the effect of ethylene gas

A

mutagenic and explosive but not generally harsh on sensitive equipment, toxic residuals from sterilisation procedure can be routinely eliminated by correct aeration

155
Q

what is produced during sterilisation using ethylene oxide

A

production of ethylene gas

156
Q

what is the advantage of formaldehyde

A

non explosive

157
Q

what are UV lamps and how do they work

A

uses short wavelength UV light to kill or inactivate microorganisms by destroying nucleic acids and disrupting their DNA

158
Q

what are the uses of UV lamps

A

not used as main sterilising agent but supplement current hospital or lab cleaning and disinfection of contaminated surfaces, may also be used for water treatment (coupled with ion sequestration and chlorine disinfection)

159
Q

what are the factors that determine efficacy of UV lamps

A

exposure time, intensity and wavelength of UV radiation, presence of interfering particles, microorganism’s UV innate resistance

160
Q

what are the bacteria found in nosocomial type infections

A

VRE, c. difficle, acinetobacter, MRSA, norovirus, e coli, klebsiella

161
Q

what is the survival time and infectious dose of VRE

A

5d-4m, <10^3 CFU

162
Q

what is the survival time and infectious dose of c. difficle

A

> 5m, 5 spores

163
Q

what is the survival time and infectious dose of acinetobacter

A

3d-5m, 250 CFU

164
Q

what is the survival time and infectious dose of MRSA

A

7d-7m, 4 CFU

165
Q

what is the survival time and infectious dose of norovirus

A

8h-7d, <20 virons

166
Q

what is the survival time and infectious dose of e coli

A

2h-16m, 10^2-5 CFU

167
Q

what is the survival time and infectious dose of klebsiella

A

2h-30m, 10^2 CFU

168
Q

what are the disinfectants affecting nucleus and its moa

A

acridines - intercalation of RNA/ DNA
halogens - inhibition of DNA
peroxides, silver - DNA breakage

169
Q

what are the disinfectants affecting cell wall/ cytoplasmic membrane and its moa

A

QAC, chlorhexidine - membrane damage or cytoplasm congealing at high conc
diamines - leakage of AA
alexidine, biguanides - lipid phase separation
phenols - leakage

170
Q

what are the disinfectants affecting proteins and its moa

A

aldehydes - cross linking of proteins and RNA/DNA
silver - interaction with thiol groups of proteins
halogens, peroxides - oxidation of thiol groups of protein to sulfoxides

171
Q

what are the disinfectants affecting the capsule and its moa

A

glutaraldehyde, EDTA - cross linking of proteins, removal of Mg+ and LPS (for gram neg)

172
Q

what are acridines

A

dye that gives colour but is also an intercalating agent that disrupts RNA and DNA

173
Q

what is EDTA

A

anticoagulating agent to keep blood by removing Ca2+ ions

174
Q

summary of activity of disinfectants

A

alcohols - vegetative yes, spores no, lipovirus yes, HIV yes, TB no
aldehydes - vegetative yes, spores yes, lipovirus yes, nonlipid yes, HIV yes, HBV yes, TB yes
chlorine compounds - vegetative yes, spores yes, lipovirus yes, nonlipid yes, HIV yes, HBV yes, TB yes
iodophors - vegetative yes, spores no, lipovirus yes, nonlipid virus, yes, HIV yes, TB yes
phenolics - vegetative yes, spores no, lipovirus yes, HIV yes, TB yes
QAC - vegetative yes, spores, yes, lipovirus yes, nonlipid no, HIV yes, HBV no

pr3151 (12 decks)

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