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disinfect Flashcards

1
Q

Sterilisation

A

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

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2
Q

chemical sterilants can _

A

destroy all forms of microbiologic life

Sporicidal at shorter exposure period

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3
Q

Disinfection

A

process that eliminates many/ all pathogenic microorgnism except bacterial spores on inanimate objects

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4
Q

8 factors that affect efficacy of both disinfection and sterilisation

A
  • Prior cleaning of object
  • Organic and inorganic load present
  • Type, level of microbial contamination
  • Conc and exposure time to germicide
  • Physical nature of object
  • Presence of biofilms
  • physical and chem factors (temp, pH, humid, water hardness)
  • innate resistance of microorg
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5
Q

Antiseptics

A

germicides applied to living tissue and skin

  • Used onto skin and not for surface disinfection
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6
Q

Antimicrobials

A

applied only to INANIMATE OBJECTS

NOT used for skin antiseptics – injure skin and other tissues

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7
Q

HIGH LVL disinfectant

A

kill all microorg but large number of bact spores
kill spores at shorter exposure periods (<3-12hrs)

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8
Q

Low level

A

kill vegetative bact, some fungi, some viruses

In PRACTICAL PERIOD OF TIME

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9
Q

biocides

A

Antiseptics, disinfectants

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10
Q

sterilisation vs disinfectant

A

disinfectant not sporicidal

may kill at prolonged 3-12hr exposure

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11
Q

cleaning

A

removal of visible soil from objects and surfaces

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12
Q

how to clean

A
  • Manually or mechanically using water w/ detergents or enzymatic pdts
  • Thorough cleaning” because inorganic and organic material remain on surfaces of instruments○ Interfere with effectiveness of sterilsiation/ disinfection
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13
Q

Decontamination

A

removes pathogenic microorg from objects so they are safe to handle, use, discard (gloves etc)

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14
Q

range of activity for biocides

A
  • Fight microorg on non-living surfaces and human skin
  • Broader spectrum of activity than AB
  • May have multiple targets
  • Range in antimicrobial activity

□ -static: agents that inhibit growth
□ -cidal: agents which kill the target organism

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15
Q

Bacteria

A

a. Free-living org, often consist of 1 biological cell
b. Bact envelope: polysacc layer, lie outside cell envelope

i. Gram -ve: thin peptidoglycan layer + outer mem

Gram +ve: THICK peptidoglycan layer + no outer mem

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16
Q

Fungi (mold)

A

Eukaryotic org that includes microorg: yeasts, molds

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17
Q

Spores (fungal spores)

A

Unit of sexual or asexual reproduction adapted for dispersal

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18
Q

Virus

A

a. Sub-microscopic infectious organisms that replicate inside biological cell

b. Non-enveloped virus

c. Enveloped virus: phospholipids and proteins with some viral glycoproteins

d. Capsid: oligomeric protomers between genome and envelope

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19
Q

Prions

A

Misfolded proteins that may transmit their misfolded shape onto normal variants

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20
Q

Number of microbes

A
  • Larger number of microbes, more time germicide need to destroy all
  • Preliminary cleaning – soap
    • Incr margin of safety
    • Shorten exposure time required to kill entire microbial load
      ○ Decr number of microorg
      ○ Physically remove them
  • Location of microorg also must be considered when factors affecting efficacy of germicide are assessed (nooks, cranny?)
    Direct contact is necessary
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21
Q

innate resistance of microorg

Microorg vary greatly in resistance to chemical germicides and sterilisation processes:

A
  • Spores:
    ○ are resistant to disinfectants
    ○ because spore coat and cortex = Acts as a barrier
  • Mycobacteria:
    ○ Waxy cell wall prevents disinfectant entry
  • Gram neg bact
    Possess outer mem + thin peptidoglycan act as barrier to uptake of disinfectants
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22
Q

Conc and potency of disinfectant

A
  • More conc disinfectant = greater efficacy
  • More conc = shorter duration to achieve disinfestation
    • But not LINEAR
  • Duration is impt!: PRACTICAL amt of time
    Fast to achieve results
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23
Q

Physical and chemical factors – TEMP

A
  • Most disinfectant incr as temp incr
    ○ Stable: Quaternary ammonium compound
  • But can have degradation too
    Unstable: ethanol volatile
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24
Q

pH

A

Alter antimicrobial activity by altering disinfectant mole or the microog cell surface

  • Incr pH improve antimicrobial activity of:
    ○ (basic conditions) glutaraldehyde, quaternary ammonium compound
    § Allow disinfectant to be more effective
  • Decr pH (acidic) Acidic destroys, weaken outer mem of bact, virus
    ○ Phenols, hypochlorites, iodine
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25
Q

relative humidity

A
  • Influence activity of gaseous disinfectant:
    ○ ethanol, chlorine dioxide, formaldehyde

Gas disinfectant + stabiliser + water: dissolves, more effec

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26
Q

water hardness

A

Reduce rate of kill of certain disinfectants because divalent cations (Ca, Mg) in the hard water interact with disinfectant to form insoluble ppt

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27
Q

Organic and inorganic matte

A

Organic matter (serum, blood, pus, fecal) interfere with antimicrobial activity of disinfectants in 2 ways ** clean before

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28
Q

Chemical reaction between germicide and organic matter

A

Reduction in potency

Full chemical inactivation

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29
Q

Protection by occlusion in salt crystals

(presence of inorganic matter)

A

a. Ppt or inclusion (rare)

Disinfectant is shielded by salts

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30
Q

Duration of exposure

A
  • Items or surfaces must be exposed to germicide for appropriate minimum contact time
  • Time depends on potency and conc of disinfectant

○ Some take 2min, other microorg take 25mins
= 25mins for effective killing

  • Set on the most resistant microorg
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31
Q

biofilm

A

Biofilms = microbial community that are tightly attached to surfaces, cannot be easily removed

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32
Q

biofilm mechanism

A
  • Microbes within them can be resistant to disinfectants by multiple mechanism:
    ○ Layer of older biofilm
    ○ Genotypic variation – mutation
    ○ Neutralising enzymes – affect mem
    ○ Physiologic conditions – (inside)
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33
Q

CHEMICAL DISINFECTANTS

contains:

A
  • Active ingredient: in disinfectant to kill pathogens
    ○ Disrupt/ damage cell
  • Excipient: emollient or surfactant
    ○ Aid by other ingredients, used in combi to help penetration of disinfectant
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34
Q

1) alochol MOA

A
  1. bacteriostatic
  2. Lead to denaturation of proteins
    a. Mechanism incr by water
    b. Penetrate proteins faster
  • Optimal in 60-90% range
    >95% not effective as water needed to denature proteins
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35
Q

alcohol antimicrobial effect

A
  • Against vegetative bacteria
    ○ Mycobacteria
    ○ No TB
  • Virus
    ○ (not definitive for lipo/ non-lipid virus)
    ○ Non enveloped (not isopropanol)
  • Fungi
  • NOT SPORICIDAL
  • Hard-surface disinfection and skin antisepsis
  • combi with other excipients/ biocides
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36
Q

diff alcohols

A

ISOPROPYL (lipo)
- bacteria and virus (non-enveloped)

ETHYL ALCOHOL
- enveloped virus

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37
Q

pros vs cons of alcohol

A
  • evaporative, no residue
  • limit activity to presence of organic matter
  • flammable
  • damage to rubber, plastic
  • irritates injured skin
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38
Q

2) ammonia MOA

A
  • Saponifying lipids
    1. Same as soap, surfactant
      ○ pH 11-12
  • In aq sol: NH3 deprotonates a small fraction of water to give ammonium and hydroxide
  • NH3 + H2O <–> NH4+ + OH-
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39
Q

ammonia effect

A
  • Envelopes of microorg

General purpose cleaner for many surfaces: glass, stainless steel

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40
Q

ammonia cons

A

Irritant for eyes
GIT

-mixed with bleach
Release toxic chloramine

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41
Q

3) aldehyde MOA

A
  • Biocidal activity of aldehydes
  1. Biocidal by alkylation of
    a. Sulfhydryl
    b. Hydroxyl
    c. Carboxyl
    d. Amino grp of microorg
  2. Alter RNA, DNA, protein synthesis
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42
Q

aldehyde effect

A

spores = high conc, int w/ outer cell layer

mycobact = int w/ mycobact cell wall

+/- bact = cross link aa grps. inhibit transport process into cell

fungi = int w/ chitin

virus = DNA crosslink, caspid changes

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43
Q

eg of aldehydes

A

FORMALDEHYDE (depends on humidity, temp)

GLUTERALDEHYDE (pH, temp, organic matter – endoscope)

Paraformaldehyde
- solid of formaldehyde (to be vapourised by heat)

Ortho-phthalaldehyde (OPA)

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44
Q

OPA

  • Solution clear, pale blue lq pH 7.5
A

○ Stable over wide range pH
○ NON-IRRITANT (eye, nose, no odour)
○ Good compatibility
* Cross-link agent
* Block spore germination
○ Interact w/ aa, prot, microorg
○ Lipophilicity assist uptake across outer layers
§ of mycobact
Gram =ve

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45
Q

pros and cons of aldehydes

A
  • non-corrosive to metal, rubber, plastic
  • highly irritating, toxic w/ contact or inhalation (PPE)
    -odor
  • OPA = stain proteins grey
46
Q

4) Biguanides consist of

have 2 biguanide moieties

A

chlorhexidine + alexidine

47
Q

chlorhexidine MOA

A
  • pH dependent (5-7)
  • Inactivate by soap, detergent
    1) Damage mem
    2) Cross cell outer mem - passive diffusion
    3) Attack bact cytoplasmic
    a. Coagulation/ gelling
    b. Inner mem
    c. Yeast, plasma mem
    4) Yeast: partition into cell wall, plasma mem, cytoplasm of cells
48
Q

chlorhexidine and alexidine effect

A
  • Broad spectrum bactericidal agent
  • cationic in sol not compaitable with ORGANIC MATTER, anionic materials
  • compaitable with cationic, nonionic surfactants
  • pH dependent (5-7)

○ react w/ -ve charge grp on cell mem, alter permeability
○ Effect on bacterial, yeast
○ Not sporicidal
○ Not fungi
○ Not mycobactericidal

49
Q

chlorhexidine uses

A
  • antimicrobial preservative (eye drop)
  • skin disinfectant
  • antiseptic creams, mouthwash, bladder irrigation, sprays, medicated dressings
50
Q

chlorhexidine uses

A
  • antimicrobial preservative (eye drop)
  • skin disinfectant
  • antiseptic creams, mouthwash, bladder irrigation, sprays, medicated dressings
51
Q

alexidine differs from chlorhexidine by:
- MOA

A
  • Contain ethylhexyl end grp
  • Faster onset of bactericidal activity
  • Produce faster alteration in bactericidal permeability
    1) Produce lipid phase separation
    2) Destruction of bacterial mem
52
Q

5) chlorine compounds eg

A

hypochlorite (lq – Na) (solid – Ca hypochlorite)

chloramine
sodium dichloroisocyanurate tabs

53
Q

Hypochlorite dissociation

A

undissociated hypochlorous acid (HOCl), electroneg, more microbicidal activity

HOCL –> H+ + OCL-

(OCL-: less activity)
more dissociation when incr pH, less efficacy

54
Q

hypochlorite MOA

A

1) Oxidation of sulfhydryl enzymes and aa
2) Ring chlorination of aa
3) Inhibit protein synthesis
4) DNA disruption
5) Loss of intracell contents

55
Q

hypochlorite effect

A
  • vegetative bacteria
  • Mycobacteria
    • TB
  • Virus
    • (lipo/ non-lipid virus)
  • Fungi
  • SPORICIDAL
  • Remove dried or fixed org and biofilms from surfaces
56
Q

hypochlorite pros and cons

A
  • Broad spectrum antimicrobial activity
    *biofilm activity
  • Do not leave toxic residues
  • Unaffected by water hardness
  • Inexpensive
  • Fast acting
  • corrodes metal
    -do not mix with ammonia (release toxic Cl gas)
  • inactivated by light
  • affected by pH
  • occular irritation, burns (GIT)
  • inactivated by organic matter
57
Q

alternative compounds that release chlorine

+ advantage

A

○ Retain Cl longer
○ Exert prolonged bactericidal effect

1) Sodium dichloroisocyanurate tablets

2) chloramine

58
Q

Sodium dichloroisocyanurate tablets effects

A

○ Retain Cl longer
○ Exert prolonged bactericidal effect
§ Tablets stable, long release
§ Microbicidal activity of sol < tablet
□ Greater than just sol

○ 50% of toal HOCL, OCl- (freee cl) avail
§ Remainder combined mono/di-chloroisocyanurate
§Free Cl used up, released to restore eqm

59
Q

SE of chlorine

A
  • Ocular irritation
  • Burns (mouth, throat, stomach)
  • Corrosiveness to metals (in high conc)
  • Inactivate by organic matter
  • Release toxic Cl gas
    • PPE needed
  • Irritate mucous mem, eye, skin
60
Q

6) iodine MOA

A
  1. Penetrate cell wall of microorg quickly
  2. Lead to disruption of protein
  3. Disruption of nucleic acid structure & synthesis
61
Q

iodophor MOA

(povidone-iodine)/ polyvinylpyrrolidone w/ iodine

A
  • Combi of iodine + solubilising agent/ carrier
    ○ Complex provides sustained release reservoir of iodine
    ○ Release small amt free I in aq sol
62
Q

bactericidal effect of I2

A
  • Dilution of iodophors adds rapid bactericidal action
    *Weaken iodine linkage to CARRIER polymer, incr free I2 in sol
63
Q

pros and cons of Iodine

A

*for general use

  • affected by pH, other chemicals (QAC inactivates)
  • inactivate in organic debris
64
Q

7) peroxygens MOA

A
  1. Acts as oxidant
    a. Produce free radicals OH*
  2. Attack essential cell components
    i. Lipids, proteins, DNA
    ii. Disrupt bact cell mem
65
Q

peroxygens formulation

A
  • Stabiliser added (but is stable)
    ○ Sodium citrate
    ○ Sodium malonate
    ○Prevent decomposition
  • Clear colourless lq
    3-90%
66
Q

eg of oxidising agents

A

1) hydrogen peroxide
2) accelerated hydrogen peroxide
3) peracetic acid

67
Q

effect of peroxygens

A

Broad-spectrum efficacy against

  • Virus
  • Bacteria
    ○ Gram +ve > -ve
    ○ But if have Catalase, peroxidase
    § Tolerance to inactivate radicals
  • Yeast
  • Bacterial spores
    ○ Higher conc 10-30%
    ○ Longer contact time
68
Q

accelerated hydrogen peroxide enhanced effect

A

1) Surfactant
i. Alkali metal, ammonium salts, alkyl sulphate
ii. Disrupt bact cell, to act on cell mem/ DNA

2) Organic acid (chelating agent)
i. Phosphoric acid, phosphonate
ii. Inactivate radicals

3) Emulsifier
i. Like salt of an alkylated diphenyl oxide
ii. Prevent dispersion, pdt keep tgt

69
Q

pros and cons of accelerated hydrogen peroxide

A
  • Disinfectant/ cleaning agent that stabilises hydrogen peroxide
    ○ Used for extended periods of time
    Medical/ veterinary device
  • short shelf life
    (decompose to H2O)
  • irritant for eyes
70
Q

peracetic acid (CH3COOOH) MOA

= hydrogen peroxide + acetic acid

A
  1. Denature proteins, enzymes
    1. Incr cell wall permeability
    2. Disrupt sulfhydryl -SH
      Sulfur S-S bonds
71
Q

peracetic acid benefits

A
  • Decomposes safe by pdts
    • Acetic acid + O2
      ○ Protein ppt, destroys nucleic acid bonds
  • More stable
    • Free from decomp by Peroxidases (in resistant bact)
    • Active in presence of organic loads
72
Q

peracetic acid effect

A

More potent biocide (low conc 0.3%) than H2O2

* Sporicidal
* Bactericidal
* Virucidal
*  fungicidal  * Low temp lq sterilant
* Medical devices
 	*environmental surface sterilant
73
Q

why use peracetic acid with salt

A

-acetic acid (vinegar) used with salts,
* lead to protein ppt

-Destroy nucleic acids bond

74
Q

8) phenols MOA

A

1) Induce leak of intracellular constituents
2) Release of K+
3) Mem damage
Make it hard to pump back K+ for eqm

75
Q

phenols effect

A
  • vegetative bacteria
  • Mycobacteria
    • TB
  • Virus
    • (lipo), HIV, enveloped
    • maybe non-lipid virus)
    • Maybe HBV
  • Fungi

Antifungal (damage plasma mem)
Antiviral properties

NOT SPORICIDAL

76
Q

eg of phenols

A

cresol
chloroxylenol

77
Q

pros and cons of phenol

A
  • residual activity in presence of organic material
  • use with soaps to incr penetration
  • water hardness reduce effectiveness
    -pH affects
78
Q

chloroxylenol

A
  • Antiseptic/ disinfectant formulation as bactericidal
  • Disrupt microbial cell wall
  • Inactivate cell enzyme
    ○ Non toxic, non irritant
    ○ Excipient for TOP pdt

Toxic if taken PO, EYE

79
Q

9) diamidines MOA

A

1) Inhibit oxygen uptake
2) Leakage of aa

bacteriostatic agent, top treatment of wound

80
Q

diamidines is from

A

Isethionate salts of 2 compounds
* Propamidine (4,4-diaminodiphenoxypropane) +
* Dibromopropamidine (2,2-dibromo-4,4-diamino

81
Q

10) silver (Ag+) compounds eg

A

1) silver sulfadiazine
2) silver metal
3) silver acetate
4) silver nitrate

82
Q

silver nitrate MOA

A

1) Interaction with thiol (sulfydryl -SH grp) in enzymes, prot
2) Affect:
a. microbial plasma
b. Cytoplasmic mem
c. Nucleic acids

83
Q

Silver sulfadiazine MOA

  • Antiseptic to 1st/ 2nd degree burn
    Prevents infection
A
  • Combi of 2 antibact:
    ○ Silver + sulfadiazine (Ab)
    1) Induce mem blebs (in susceptible bact)
    2) Broader spectrum > nitrate
84
Q

11) mercuric chloride (HgCl2) MOA

A

1) Affect microbial peptide synthesis

Used to treat syphilis but risk > benefit

broad range disinfectant

85
Q

risk of mercuric

A
  • Highly toxic
  • Accumulate in kidney (Hg)
    • AK failure
    • corrosive
86
Q

12) quaternary ammonium compounds (QAC) eg

A

benzalkonium chloride
cetrimide (also acts as cationic surfactant)

87
Q

12) quaternary ammonium compounds (QAC) structure

A
  • Cationic detergents, better ar neut~ alkaline pH
    • Inactive by organic matter, detergent, soap
  • Organically sub ammonium compounds
    • N atom have valence of 5

○ 4 sub radicals: R1-4
§ Alkyl or heterocyclic radicals
§ Given size or chain length

○ 5th: A-
halide, sulfate, similar radical

88
Q

QAC action

A

1) Adsorption and penetrate agent into cell wall

2) Reaction w/ cytoplasmic mem (lipid/ prot) phospholipids
a. Followed by mem disorganization

3) Leak intracellular low-Mr material

4) Degradation of proteins, nucleic acids
Wall lysis caused by autolytic enzymes
- impair permeability

89
Q

QAC uses

A
  • Pre-op disinfections of unbroken skin
  • Application to mucous mem
  • Disinfection of noncritical surfaces
    Floor, furniture, walls
90
Q

QAC effect

A
  • Fungicidal
  • Bactericidal
  • Virucidal – lipo, enveloped virus
  • vegetative bacteria
  • Mycobacteria
    • Maybe TB
    • Gram +ve
  • Virus
    • (lipo), HIV, enveloped virus
      ○ No non-lipid virus)
      ○ No HBV
      ○ no mycobact
  • Fungi
  • But sporistaticNOT sporicidal
91
Q

QAC pros and cons

A
  • residual effect (bacterostatic surface for brief time)
  • active at neut/ alkaline pH (9-10) (not acidc <3.5)
  • stable in storage
  • inactivate by water hardness
  • inact by organic matter, detergents, soap, hard water
92
Q

benzalkonium chloride (QAC) uses

A
  • Antimicrobial preservative
    ○ COMBI w/ similar cationic surfactants
    § Cetrimide
  • Active against:
    ○ Bact (gram +ve), yeast, fungi
    ○ Minimal against:
    § bact endospores
    § acid-fast bact
93
Q

Benzalkonium chloride activity depends on

A
  • Sig dependent upon: alkyl composition of homolog mixture
94
Q

Benzalkonium chloride SE?

A

○ Non-irritant, non-sensitising, well tolerate in dilutions
Skin, mucous mem

95
Q

plant based disinfectants

A

eucalyptus

* Steam distillation method 
* Effect vie against: 
	○ Escherichia coli
	○ Staphylococcus aureus  Disinfectant for mining
96
Q

vapour phase sterilants useful for

A
  • Heat sensitive medical devices, surgical supplies:
    Use lq sterilants
    • Vapour-phase sterilisation
    • “cold” systems
97
Q

lq sterilent

A

Glutaraldehyde, peracetic acid, hydrogen peroxide

98
Q

“cold” systems sterilent

A

Ethylene oxide, < formaldehyde, hydrogen peroxide, peracetic acid

99
Q

Ethylene oxide, formaldehyde MOA

A
  • Broad spectrum alkylating agent

1) Attack proteins, nucleic acids, other organic compounds

2) Reactive with
a. Sulfhydryl
Enzyme-reactive grps

100
Q

ethylene oxide disadv vs formaldehyde adv

A
  • Gas: mutagenic, explosive, not harsh on sensitive equip
    ○ Toxic residues = eliminate by correct aeration
    ○ Prevent contamination

Formaldehyde gas: similar MOA
* Non explosive
(Not widely used in healthcare)

101
Q

UV lamps disinfectant MOA

A
  • Short-wavelength UV light
  • Kill or inactivate microorg
    ○ Destroys nucleic acid
    ○ Disrupt DNA
102
Q

UV rays applications

A
  • Supplement hosp, lab cleaning
  • Disinfect of contaminated surfaces
  • Water treatment
    • Combi w/ ion sequestration
      Chlorine disinfection
  • inactivate virus, mycoplasma, bact, fungi
103
Q

UV rays effectiveness factors

A

1) Exposure time
2) Intensity and wavelength of UV radiation
3) Presence of interfering particles
4) Line-of-sight exposure of microorg to UV light
a. Repeated cycle used for proper disinfection

5) Microorg UV innate resistance

104
Q

nosocomial infections

A
  • Environment may facilitate transmission of several impt healthcare-associated pathogens
      ○ VRE: vancomycin-resistant enterococci 
  ○ CDAD: clostridium difficile 
  ○ MRSA: methicillin -resistant staphylococcus aureus 
  ○ Norovirus
  ○ Acinetobacter spp.
105
Q

disinfect water

A

1) UV rays
2) ozone

3) ion sequestration (cl)
- chloramine

105
Q

sequestrating

A

chelating agents. chelates with alkaline earth and heavy metal ions (metal-edetate complex)

  • affected by ions, pH

prevents autoxidation reactions

106
Q

cetrimide

A

QAC
cationic surfactant
antimicrobial preservative

combi with benzalkonium chloride

  • used in skin, burns, wounds
107
Q

disinfectants vs AB

A

both affected by efflux pumps resistance

disinfectant induce denaturation, not affected by small struc modifications

disinfectants affected by the physical protection

108
Q

biofilms evolution

A

sub-MIC conc trigger stress response in bact

induce temp, adaptive changes in composition// permeability of cell envelope// activity of efflux pumps

use of disinfectant remove weaker bact, more resource for surviving bact (conc/ duration/ improper disinfectant used)

109
Q

contact time affected by

A

disinfectants work within minutes

some bact reside in places that are difficult to reach

disinfectants dissipate too fast

110
Q

biofilms key points of resistance

A

genotypic resistance (evolution)

layer of older (physical protection + neut enzymes)
change in physiologic conditions (difficult to achieve)
adhesive to surface (for growth of biofilm, less impt for survive)

111
Q

why not use peracetic acid// accelerated hydrogen peroxide

A

peracetic –> acetic acid released, residue

acc HP –> surfactant, chelating agent, emulsifier need to be removed

3151 disinfect (6 decks)

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