disinfect Flashcards
Sterilisation
process that destroys or eliminates all forms of microbial life and is carried out in healthcare facilities by – physical or chemical methods
chemical sterilants can _
destroy all forms of microbiologic life
Sporicidal at shorter exposure period
Disinfection
process that eliminates many/ all pathogenic microorgnism except bacterial spores on inanimate objects
8 factors that affect efficacy of both disinfection and sterilisation
- 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
Antiseptics
germicides applied to living tissue and skin
- Used onto skin and not for surface disinfection
Antimicrobials
applied only to INANIMATE OBJECTS
NOT used for skin antiseptics – injure skin and other tissues
HIGH LVL disinfectant
kill all microorg but large number of bact spores
kill spores at shorter exposure periods (<3-12hrs)
Low level
kill vegetative bact, some fungi, some viruses
In PRACTICAL PERIOD OF TIME
biocides
Antiseptics, disinfectants
sterilisation vs disinfectant
disinfectant not sporicidal
may kill at prolonged 3-12hr exposure
cleaning
removal of visible soil from objects and surfaces
how to clean
- 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
Decontamination
removes pathogenic microorg from objects so they are safe to handle, use, discard (gloves etc)
range of activity for biocides
- 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
Bacteria
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
Fungi (mold)
Eukaryotic org that includes microorg: yeasts, molds
Spores (fungal spores)
Unit of sexual or asexual reproduction adapted for dispersal
Virus
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
Prions
Misfolded proteins that may transmit their misfolded shape onto normal variants
Number of microbes
- 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
innate resistance of microorg
Microorg vary greatly in resistance to chemical germicides and sterilisation processes:
- 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
Conc and potency of disinfectant
- 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
Physical and chemical factors – TEMP
- Most disinfectant incr as temp incr
○ Stable: Quaternary ammonium compound - But can have degradation too
Unstable: ethanol volatile
pH
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
relative humidity
- Influence activity of gaseous disinfectant:
○ ethanol, chlorine dioxide, formaldehyde
Gas disinfectant + stabiliser + water: dissolves, more effec
water hardness
Reduce rate of kill of certain disinfectants because divalent cations (Ca, Mg) in the hard water interact with disinfectant to form insoluble ppt
Organic and inorganic matte
Organic matter (serum, blood, pus, fecal) interfere with antimicrobial activity of disinfectants in 2 ways ** clean before
Chemical reaction between germicide and organic matter
Reduction in potency
Full chemical inactivation
Protection by occlusion in salt crystals
(presence of inorganic matter)
a. Ppt or inclusion (rare)
Disinfectant is shielded by salts
Duration of exposure
- 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
biofilm
Biofilms = microbial community that are tightly attached to surfaces, cannot be easily removed
biofilm mechanism
- 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)
CHEMICAL DISINFECTANTS
contains:
- 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
1) alochol MOA
- bacteriostatic
- 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
alcohol antimicrobial effect
- 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
diff alcohols
ISOPROPYL (lipo)
- bacteria and virus (non-enveloped)
ETHYL ALCOHOL
- enveloped virus
pros vs cons of alcohol
- evaporative, no residue
- limit activity to presence of organic matter
- flammable
- damage to rubber, plastic
- irritates injured skin
2) ammonia MOA
- Saponifying lipids
- Same as soap, surfactant
○ pH 11-12
- Same as soap, surfactant
- In aq sol: NH3 deprotonates a small fraction of water to give ammonium and hydroxide
- NH3 + H2O <–> NH4+ + OH-
ammonia effect
- Envelopes of microorg
General purpose cleaner for many surfaces: glass, stainless steel
ammonia cons
Irritant for eyes
GIT
-mixed with bleach
Release toxic chloramine
3) aldehyde MOA
- Biocidal activity of aldehydes
- Biocidal by alkylation of
a. Sulfhydryl
b. Hydroxyl
c. Carboxyl
d. Amino grp of microorg - Alter RNA, DNA, protein synthesis
aldehyde effect
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
eg of aldehydes
FORMALDEHYDE (depends on humidity, temp)
GLUTERALDEHYDE (pH, temp, organic matter – endoscope)
Paraformaldehyde
- solid of formaldehyde (to be vapourised by heat)
Ortho-phthalaldehyde (OPA)
OPA
- Solution clear, pale blue lq pH 7.5
○ 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
pros and cons of aldehydes
- non-corrosive to metal, rubber, plastic
- highly irritating, toxic w/ contact or inhalation (PPE)
-odor - OPA = stain proteins grey
4) Biguanides consist of
have 2 biguanide moieties
chlorhexidine + alexidine
chlorhexidine MOA
- 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
chlorhexidine and alexidine effect
- 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
chlorhexidine uses
- antimicrobial preservative (eye drop)
- skin disinfectant
- antiseptic creams, mouthwash, bladder irrigation, sprays, medicated dressings
chlorhexidine uses
- antimicrobial preservative (eye drop)
- skin disinfectant
- antiseptic creams, mouthwash, bladder irrigation, sprays, medicated dressings
alexidine differs from chlorhexidine by:
- MOA
- 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
5) chlorine compounds eg
hypochlorite (lq – Na) (solid – Ca hypochlorite)
chloramine
sodium dichloroisocyanurate tabs
Hypochlorite dissociation
undissociated hypochlorous acid (HOCl), electroneg, more microbicidal activity
HOCL –> H+ + OCL-
(OCL-: less activity)
more dissociation when incr pH, less efficacy
hypochlorite MOA
1) Oxidation of sulfhydryl enzymes and aa
2) Ring chlorination of aa
3) Inhibit protein synthesis
4) DNA disruption
5) Loss of intracell contents
hypochlorite effect
- vegetative bacteria
- Mycobacteria
- TB
- Virus
- (lipo/ non-lipid virus)
- Fungi
- SPORICIDAL
- Remove dried or fixed org and biofilms from surfaces
hypochlorite pros and cons
- 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
alternative compounds that release chlorine
+ advantage
○ Retain Cl longer
○ Exert prolonged bactericidal effect
1) Sodium dichloroisocyanurate tablets
2) chloramine
Sodium dichloroisocyanurate tablets effects
○ 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
SE of chlorine
- 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
6) iodine MOA
- Penetrate cell wall of microorg quickly
- Lead to disruption of protein
- Disruption of nucleic acid structure & synthesis
iodophor MOA
(povidone-iodine)/ polyvinylpyrrolidone w/ iodine
- Combi of iodine + solubilising agent/ carrier
○ Complex provides sustained release reservoir of iodine
○ Release small amt free I in aq sol
bactericidal effect of I2
- Dilution of iodophors adds rapid bactericidal action
*Weaken iodine linkage to CARRIER polymer, incr free I2 in sol
pros and cons of Iodine
*for general use
- affected by pH, other chemicals (QAC inactivates)
- inactivate in organic debris
7) peroxygens MOA
- Acts as oxidant
a. Produce free radicals OH* - Attack essential cell components
i. Lipids, proteins, DNA
ii. Disrupt bact cell mem
peroxygens formulation
- Stabiliser added (but is stable)
○ Sodium citrate
○ Sodium malonate
○Prevent decomposition - Clear colourless lq
3-90%
eg of oxidising agents
1) hydrogen peroxide
2) accelerated hydrogen peroxide
3) peracetic acid
effect of peroxygens
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
accelerated hydrogen peroxide enhanced effect
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
pros and cons of accelerated hydrogen peroxide
- 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
peracetic acid (CH3COOOH) MOA
= hydrogen peroxide + acetic acid
- Denature proteins, enzymes
- Incr cell wall permeability
- Disrupt sulfhydryl -SH
Sulfur S-S bonds
peracetic acid benefits
- Decomposes safe by pdts
- Acetic acid + O2
○ Protein ppt, destroys nucleic acid bonds
- Acetic acid + O2
- More stable
- Free from decomp by Peroxidases (in resistant bact)
- Active in presence of organic loads
peracetic acid effect
More potent biocide (low conc 0.3%) than H2O2
* Sporicidal * Bactericidal * Virucidal * fungicidal * Low temp lq sterilant * Medical devices *environmental surface sterilant
why use peracetic acid with salt
-acetic acid (vinegar) used with salts,
* lead to protein ppt
-Destroy nucleic acids bond
8) phenols MOA
1) Induce leak of intracellular constituents
2) Release of K+
3) Mem damage
Make it hard to pump back K+ for eqm
phenols effect
- vegetative bacteria
- Mycobacteria
- TB
- Virus
- (lipo), HIV, enveloped
- maybe non-lipid virus)
- Maybe HBV
- Fungi
Antifungal (damage plasma mem)
Antiviral properties
NOT SPORICIDAL
eg of phenols
cresol
chloroxylenol
pros and cons of phenol
- residual activity in presence of organic material
- use with soaps to incr penetration
- water hardness reduce effectiveness
-pH affects
chloroxylenol
- 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
9) diamidines MOA
1) Inhibit oxygen uptake
2) Leakage of aa
bacteriostatic agent, top treatment of wound
diamidines is from
Isethionate salts of 2 compounds
* Propamidine (4,4-diaminodiphenoxypropane) +
* Dibromopropamidine (2,2-dibromo-4,4-diamino
10) silver (Ag+) compounds eg
1) silver sulfadiazine
2) silver metal
3) silver acetate
4) silver nitrate
silver nitrate MOA
1) Interaction with thiol (sulfydryl -SH grp) in enzymes, prot
2) Affect:
a. microbial plasma
b. Cytoplasmic mem
c. Nucleic acids
Silver sulfadiazine MOA
- Antiseptic to 1st/ 2nd degree burn
Prevents infection
- Combi of 2 antibact:
○ Silver + sulfadiazine (Ab)
1) Induce mem blebs (in susceptible bact)
2) Broader spectrum > nitrate
11) mercuric chloride (HgCl2) MOA
1) Affect microbial peptide synthesis
Used to treat syphilis but risk > benefit
broad range disinfectant
risk of mercuric
- Highly toxic
- Accumulate in kidney (Hg)
- AK failure
- corrosive
12) quaternary ammonium compounds (QAC) eg
benzalkonium chloride
cetrimide (also acts as cationic surfactant)
12) quaternary ammonium compounds (QAC) structure
- 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
QAC action
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
QAC uses
- Pre-op disinfections of unbroken skin
- Application to mucous mem
- Disinfection of noncritical surfaces
Floor, furniture, walls
QAC effect
- 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
- (lipo), HIV, enveloped virus
- Fungi
- But sporistaticNOT sporicidal
QAC pros and cons
- 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
benzalkonium chloride (QAC) uses
- Antimicrobial preservative
○ COMBI w/ similar cationic surfactants
§ Cetrimide - Active against:
○ Bact (gram +ve), yeast, fungi
○ Minimal against:
§ bact endospores
§ acid-fast bact
Benzalkonium chloride activity depends on
- Sig dependent upon: alkyl composition of homolog mixture
Benzalkonium chloride SE?
○ Non-irritant, non-sensitising, well tolerate in dilutions
Skin, mucous mem
plant based disinfectants
eucalyptus
* Steam distillation method * Effect vie against: ○ Escherichia coli ○ Staphylococcus aureus Disinfectant for mining
vapour phase sterilants useful for
- Heat sensitive medical devices, surgical supplies:
Use lq sterilants- Vapour-phase sterilisation
- “cold” systems
lq sterilent
Glutaraldehyde, peracetic acid, hydrogen peroxide
“cold” systems sterilent
Ethylene oxide, < formaldehyde, hydrogen peroxide, peracetic acid
Ethylene oxide, formaldehyde MOA
- Broad spectrum alkylating agent
1) Attack proteins, nucleic acids, other organic compounds
2) Reactive with
a. Sulfhydryl
Enzyme-reactive grps
ethylene oxide disadv vs formaldehyde adv
- 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)
UV lamps disinfectant MOA
- Short-wavelength UV light
- Kill or inactivate microorg
○ Destroys nucleic acid
○ Disrupt DNA
UV rays applications
- Supplement hosp, lab cleaning
- Disinfect of contaminated surfaces
- Water treatment
- Combi w/ ion sequestration
Chlorine disinfection
- Combi w/ ion sequestration
- inactivate virus, mycoplasma, bact, fungi
UV rays effectiveness factors
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
nosocomial infections
- 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.
disinfect water
1) UV rays
2) ozone
3) ion sequestration (cl)
- chloramine
sequestrating
chelating agents. chelates with alkaline earth and heavy metal ions (metal-edetate complex)
- affected by ions, pH
prevents autoxidation reactions
cetrimide
QAC
cationic surfactant
antimicrobial preservative
combi with benzalkonium chloride
- used in skin, burns, wounds
disinfectants vs AB
both affected by efflux pumps resistance
disinfectant induce denaturation, not affected by small struc modifications
disinfectants affected by the physical protection
biofilms evolution
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)
contact time affected by
disinfectants work within minutes
some bact reside in places that are difficult to reach
disinfectants dissipate too fast
biofilms key points of resistance
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)
why not use peracetic acid// accelerated hydrogen peroxide
peracetic –> acetic acid released, residue
acc HP –> surfactant, chelating agent, emulsifier need to be removed
