disinfectants Flashcards
what is sterilisation
process that destroys or eliminates all forms of microbial life and is carried out in healthcare facilities by physical or chemical methods, sporicidal
what are chemical sterilants
chemicals that are used to destroy all forms of microbial life
can chemical sterilants kill spores
yes with prolonged exposure
what is disinfection
process that eliminates many or all pathogenic microorganisms, except bacterial spores on inanimate objects, non sporicidal
what is high level disinfection
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
what is low level disinfection
kills most vegetative bacteria, some fungi, some viruses in a practical amount of time
what is cleaning
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
what is decontamination
removal of pathogenic microorganisms from objects so they are safe to handle, use or discard
what processes constitutes as decontamination
disinfection, sterilisation, antisepsis
what is the difference between antiseptics and disinfectants
antiseptics are germicides applied only to skin while disinfectants are antimicrobials only applied to inanimate objects as it can injure skin and other tissues
what constitutes as biocides
antiseptics and disinfectants
what are the biocides used for
to fight microorganisms on human skin and on nonliving surfaces
what is the difference between biocides and abx
biocides have broader spectrum of activity than abx and may have multiple targets
what kind of activity does biocides have
-static: inhibit growth, -cidal: kill target microorganism
what are the different types of microorganisms
bacteria, fungi, spores, virus, prions
what defines as a bacteria
free living organisms often consisting of one biological cell
what defines as a fungi
eukaryotic organisms (contains nucleus)
what defines as a spore
unit of sexual or asexual reproduction adapted for dispersal
what defines as a virus
sub microscopic infectious microorganisms that replicate inside biological cell
what defines as a prion
misfolded proteins that may transmit their misfolded shape onto normal variants
what is a bacterial envelope
polysaccharide layer that lies outside the cell envelope
what is the difference between gram pos and gram neg
gram pos has no outer membrane while gram neg has a thin peptidoglycan layer with outer membrane
what is the difference between nonenveloped and enveloped virus
nonenveloped virus lacks lipid membrane while an enveloped virus has phospholipids and proteins with some viral glycoprotein
what is a capsid
oligomeric protomers between genome and envelop
what is the role of the capsid
acts as a protein shell of a virus, enclosing its genetic material
what is the activity of germicides dependent on
activity of germicides against microorganisms depends on intrinsic qualities of the organism, chemical and external physical environment
what are the factors that affect the efficacy of disinfection and sterilisation
number of microbes, innate resistance of organisms, conc and potency of disinfectants, chemical and physical factors, organic and inorganic matter, duration of exposure, biofilm
how does number of microbes affect efficacy of disinfection and sterilisation
more number of microbes = more killing required
what is the factor that determines the innate resistance of microorganisms
composition of outer layer
what are the main three types of microorganisms that can possess innate resistance and why
spores, mycobacteria and gram neg bacteria as they possess an outer layer
what are the different outer layers that spores, mycobacteria and gram neg bacteria have
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
how does conc and potency of disinfectants affect efficacy of disinfection and sterilisation
more conc and potent = greater efficacy and shorter time required but not linear r/s
what are the physical and chemical factors to consider when determining efficacy of disinfection and sterilisation
temp, pH, relative humidity, water hardness
hows does each physical and chemical factor affect efficacy of disinfection and sterilisation
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
which chemical disinfectant has activity increased when pH increases
glutaraldehyde, QAC
which chemical disinfectant has activity decreased when pH increases
phenols, hypochlorites, iodine
what are examples of gaseous disinfectants that would be affected by relative humidity
ethanol, chlorine dioxide, formaldehyde
how does organic and inorganic matter affect efficacy of disinfection and sterilisation
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)
what are examples of organic material
blood, serum, pus, fecal
how does duration of exposure affect efficacy of disinfection and sterilisation
longer duration of exposure = more killing done
what are biofilms
microbial communities that are tightly attached to surfaces and cannot be easily removed
what are the mechanisms in which microbes within biofilms can be resistant to disinfectants by
layers of old biofilms, genotypic variation (like of the membrane), neutralizing enzymes, physiologic conditions
what are chemical disinfectants
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
what are examples of chemical disinfectants
alcohols, ammonia, aldehyde, biguanides, chlorine and chlorine compounds, iodine and iodophors, peroxygens, accelerated h2o2, peracetic acid, phenols, chloroxylenol, diamidines, Ag compounds, mercuric chloride, QAC
what is alcohol’s spectrum of activity
against vegetative bacteria, viruses and fungi, not sporicidal
what is the optimal conc of alcohol
60-90%
what type of activity does alcohol have
bactericidal but can be bacteriostatic
how can alcohol be bacteriostatic
by inhibition of production of metabolites essential for cell division
what are the uses of alcohol
used for hard surface disinfection and skin antisepsis
what is the mechanism of action of alcohol
denatures proteins and mechanism increased by water
what is the difference in efficacy between isopropyl and ethyl alcohol
isopropyl alcohol has greater lipophilic properties than ethyl alcohol thus its more efficacious against non enveloped
what are the uses of ammonia
general purpose cleaner for many surfaces
what is the mechanism of action of ammonia
works by saponifying lipids within the envelopes of the microorganism by making a salt complex which forms a precipitation
what happens when ammonia is in aq solution
ammonia deprotonates a small fraction of water to give ammonia and hydroxide with pH 11-12
what are the disadvantages of ammonia
irritant for eyes and gastric system, releases toxic chloramine if mixed with bleach
what is chloramine
a derivative of ammonia and organic amines where one or more NH bonds is replaced by NCl bonds
what are the uses of chloramine
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
what is tri chloramine associated with
pool water
what type of activity does aldehyde have
biocidal
what is the mechanism of action of aldehyde
alkylation of sulfhydryl, hydroxyl, carboxyl and amino groups of microorganism alters RNA, DNA and protein synthesis
what are the uses of aldehyde
antisepsis, disinfection, preservation
what are the disadvantages of aldehyde
toxicity and odor
how does aldehyde interact with bacterial spores, mycobacteria, nonsporulating bacteria, fungi and viruses
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
what is an example of an aldehyde used
ortho-phthaldehyde (OPA)
what are the properties of OPA
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
what is the mechanism of action of OPA
cross linking agent that link irreversible with bacteria DNA to block and kill, block spore germination by interacting with protein, AA and microorganisms
what are some examples of biguanides
chlorhexidine, alexidine
what type of activity does chlorhexidine have
bactericidal
what are the uses of chlorhexidine
disinfectant and preservative
what type of salt is chlorhexidine in eyedrops as a preservative
0.01% of either acetate or gluconate salt
at what conc can chlorhexidine gluconate salt be used as contact lens disinfectant
0.002-0.006%
at what conc can chlorhexidine be used as skin disinfectant
0.5% in 70% ethanol
at what conc can chlorhexidine be used as a surgical scrub disinfectant
4% with detergents
what products are chlorhexidine found in
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
what types of properties does chlorhexidine have
activity is pH dependent, activity greatly reduced in organic matter, cationic thus incompatible with anionic materials and soaps (compatible with cationic and nonionic surfactants)
what happens if high conc of surfactants used with chlorhexidine
can cause micellar binding thus reducing activity
what is the mechanism of action of chlorhexidine
damages outer cell membrane and crosses by passive diffusion, followed by attacking bacterial cytoplasmic through coagulation or gelling
what is the difference in structure between alexidine and chlorhexidine
alexidine possesses ethylhexyl end groups
what is the mechanism of action of alexidine
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
what are examples of chlorine and chlorine compounds
hypochlorites, chloramine, sodium dichloroisocyanurate
what are the forms of hypochlorite
liquid form as sodium hypochlorite, solid form as calcium hypochlorite
what is the activity of hypochlorite attributed to
undissociated hypochlorous acid (HOCl)
what is the dissociation of hypochlorous acid into hypochlorite ion affected by
dissociation of HOCl into OCl- affected by pH
what happens to dissociation of hypochlorous acid into hypochlorite ion if pH increases
pH increases causes more dissociation into OCl- which decreases efficacy
what are the properties of hypochlorites
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
what are the mechanisms of hypochlorites
oxidation of sulfyhydryl enzymes and AA, ring chlorination of AA, inhibition of protein synthesis, DNA disruption, loss of intracellular contents
what are the disadvantages of hypochlorites
ocular irritation, burns mouth/throat/stomach, corrosiveness to metals in high conc, inactivation by organic matter, release of toxic chlorine gas
what is the advantage of chloramines over hypochlorites
more prolonged bactericidal effect as retains chlorine longer
what is the advantage of sodium dichloroisocyanurate over hypochlorites
more prolonged bactericidal effect as retains chlorine longer
what is the composition of sodium dichloroisocyanurate
50% of total available chlorine is free as HOCl and OCl- while remainder is combined to form mono/di-chloroisocyanurate
what are the uses of iodine
antiseptics on skin or tissue
what are the uses of iodine compounds
disinfectant and antiseptics
what is the mechanism of action of iodine
iodine can penetrate through cell wall of microorganisms and disrupt protein and nucleic acid structure and synthesis
what is the composition of iodophor
iodine and a solubilising agent
what is the mechanism of action of iodophor
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
what effect does dilution of iodophor have
more rapid action due to increased release of free iodine
what is the benefit of slow release of iodine in iodine compounds
keep conc minimum for substance to be effective for longer (same as chlorine compounds)
what are examples of peroxygens
h2o2, accelerated h2o2, peracetic acid
what are the uses of h2o2
disinfection, sterilisation, antisepsis
what are the properties of h2o2
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
what is the mechanism of action of h2o2
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
what is the mechanism of resistance to h2o2
development of specific enzymes that inactivates some of the radicals formed so less act on cell and thus less effective (more for biofilms)
what is the conc required for h2o2 to have sporicidal activity
10-30% and longer contact time
what is the disadvantage of h2o2
can be irritant at high conc if used as antiseptic
what is the difference between h2o2 and accelerated h2o2
enhanced antimicrobial efficacy from surfactant, organic acid and emulsifier
what are the surfactants that can be used for accelerated h2o2
alkali metal and ammonium salts or alkyl sulfate
what is the benefit of having a surfactant to make accelerated h2o2
makes it more effective against outer layer of cell and can penetrate more easily, acts on DNA as well
what is the benefit of having organic acid to make accelerated h2o2
chelating agent that forms complexes with salts which can activate or inactivate activity of radical
what are organic acids that can be used for accelerated h2o2
phosphoric acid or phosphonate
what are the emulsifiers that can be used for accelerated h2o2
salt of an alkylated diphenyl oxide
what is the benefit of having emulsifiers to make accelerated h2o2
size dispersion of product increases stability
what are the properties of accelerated h2o2
relatively short half life due to decomposition
what are the disadvantages of accelerated h2o2
irritant for eyes
what is the advantage of peracetic acid
more potent than h2o2
at what conc does peracetic acid have activity
0.3%
what is the mechanism of action of peracetic acid
what are the advantages of peracetic acid
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
what is peracetic acid commonly used for
low temp liquid sterilant for medical devices and environmental surfaces
what are the uses of phenol
disinfectant, antiseptic, preservative (but less common now)
what is the mechanism of action of phenol
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
what are the uses of chloroxylenol and at what conc
antiseptic (0.5%), antimicrobial (0.1-0.8%), disinfectant (2.5-5%)
what is the mechanism of action of chloroxylenol
disrupts microbial cell wall and inactivates cellular enzymes
what is chloroxylenol commonly used with
edetic acid
what are the common uses of edetic acid
chelating agents in food and cosmetics to form water-soluble complexes with alkaline metal ions
what is the metal-edetate complex stability dependent on
metal ion involved and pH
what are the uses of diamidines
antiseptic and disinfectants
what is the mechanism of action of diamidines
inhibits oxygen uptake and leakage of AA
what are examples of diamidine
isethionate salts of propamidine and dibromomidine
what are examples of Ag compounds
silver nitrate, silver sulfadiazine
what is the mechanism of action of silver nitrate
interaction with thiol (sulfydryl -SH) groups in enzymes and proteins
what is the composition of silver sulfadiazine and what is its significance
silver and sulfazine which are two antibacterial agents
what is the difference between silver nitrate and silver sulfadiazine
silber sulfadiazine has broader spectrum
what is the mechanism of action of silver sulfadiazine
induces membrane blebs in susceptible bacteria
what are the uses of mercuric chloride (HgCl2)
broad range disinfectant
what is the mechanism of action of mercuric chloride
affect microbial peptide synthesis
what is the disadvantage of mercuric chloride
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
what is an example of QAC
benzalkonium chloride
what is the structure of QAC
R1-4 are alkyl or heterocyclic radicles, A- is halide, sulfate or similar radical
what are QAC known as
cationic detergents
what are the uses of QAC
preoperative disinfection of unbroken skin, application to mucus membranes, disinfection of noncritical surfaces (floors, furniture and walls)
what type of activity does QAC have
fungicidal, bactericidal, virucidal against lipophilic viruses, not sporicidal
what is the mechanism of action of QAC
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
why cant QAC be used in open wounds
can cause autolysis of cells
what is benzalkonium chloride often in combination with and why
surfactant to disrupt outer layer as main activity is within cell
what are the properties of benzalkonium chloride
more activity against gram pos than gram neg, minimal against bacterial endospores and acid-fast bacteria, non irritating, non sensitising and well tolerated
what is activity of benzalkonium chloride dependent on
alkyl composition of homolog mixture (R)
what are examples of plant based disinfectant
eucalyptus
what are the uses of plant based disinfectant
against e coli and s. aureus, disinfectant during mining
how are plant based disinfectant produced
essential oils obtained by steam distillation method
what are examples of vapor phase sterilants
ethylene oxide, formaldehyde, h2o2, peracetic oxide
what are the uses of vapor phase sterilants
disinfect/ sterilise heat sensitive medical devices and surgical supplies
what is the mechanism of action of ethylene oxide
broad spectrum alkylating agents that attack proteins, nucleic acids and other organic compounds, particularly reative with sulfhydryl and other enzyme reactive groups
what is the mechanism of action of formaldehyde
broad spectrum alkylating agents that attacks proteins, nucleic acids and other organic compounds, particularly reactive with sulfhydryl and other enzyme reactive groups
what is the effect of ethylene gas
mutagenic and explosive but not generally harsh on sensitive equipment, toxic residuals from sterilisation procedure can be routinely eliminated by correct aeration
what is produced during sterilisation using ethylene oxide
production of ethylene gas
what is the advantage of formaldehyde
non explosive
what are UV lamps and how do they work
uses short wavelength UV light to kill or inactivate microorganisms by destroying nucleic acids and disrupting their DNA
what are the uses of UV lamps
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)
what are the factors that determine efficacy of UV lamps
exposure time, intensity and wavelength of UV radiation, presence of interfering particles, microorganism’s UV innate resistance
what are the bacteria found in nosocomial type infections
VRE, c. difficle, acinetobacter, MRSA, norovirus, e coli, klebsiella
what is the survival time and infectious dose of VRE
5d-4m, <10^3 CFU
what is the survival time and infectious dose of c. difficle
> 5m, 5 spores
what is the survival time and infectious dose of acinetobacter
3d-5m, 250 CFU
what is the survival time and infectious dose of MRSA
7d-7m, 4 CFU
what is the survival time and infectious dose of norovirus
8h-7d, <20 virons
what is the survival time and infectious dose of e coli
2h-16m, 10^2-5 CFU
what is the survival time and infectious dose of klebsiella
2h-30m, 10^2 CFU
what are the disinfectants affecting nucleus and its moa
acridines - intercalation of RNA/ DNA
halogens - inhibition of DNA
peroxides, silver - DNA breakage
what are the disinfectants affecting cell wall/ cytoplasmic membrane and its moa
QAC, chlorhexidine - membrane damage or cytoplasm congealing at high conc
diamines - leakage of AA
alexidine, biguanides - lipid phase separation
phenols - leakage
what are the disinfectants affecting proteins and its moa
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
what are the disinfectants affecting the capsule and its moa
glutaraldehyde, EDTA - cross linking of proteins, removal of Mg+ and LPS (for gram neg)
what are acridines
dye that gives colour but is also an intercalating agent that disrupts RNA and DNA
what is EDTA
anticoagulating agent to keep blood by removing Ca2+ ions
summary of activity of disinfectants
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
