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Animal Hygiene final > Chemical methods of sterilization and disinfection > Flashcards

Chemical methods of sterilization and disinfection Flashcards

1
Q

Chemical methods

A
  • Antiseptics - Skin, mucous membranes
  • Disinfectants
  • Environment
  • Types: Alcohol, Chloride and chlorine-based compounds, Iodine-based compounds, Aldehydes, Peroxide based compounds, Surfactants (tensids), Acids and alkalis, Miscellaneous
  • Ideal disinfectant: Wide spectrum, Quick, Irreversible effect, Long lasting, Contamination has no negative effect, Not toxic, water-soluble, Not corrosive, cheap, Not flammable, Easy to use, odorless, Stable, Cleans, No environmental problems
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2
Q

Alcohols

A
  • ethyl-, isopropil-alcohol,
  • mixture of ethyl-and isopropyl-alcohol etc.;
  • disinfection based on water extraction
  • greater effect on the Gram-negative vegetative bacteria
  • used in combination with other disinfectants
  • used for skin disinfection
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3
Q

Chlorine based compounds in general

A
  • at room temp: yellow-greenish, suffocating, oxic gas
  • water soluble, forms hypochloric acid (HOCl) which dissociates into HO and active chlorine
  • active chlorine: strong germicide effect, penetrates cell membrane, destroys cellular enzyme
  • highly volatile -> increased temp reduces capacity, over 30-40oC no capacity
  • organic materials decrease capacity
  • corrosive - metal, rubber, plastic
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4
Q

Sodium hypochloride

A
  • very common
  • 5-15% active chlorine and 1-3% sodium hydroxide
  • NaOH gives stability to active chloride BUT corrosive on metals, skin irritation
  • conc. 3-5% -> vegetative form of bacteria and all viruses BUT not destroy: acid fast bacteria, spores (over 15% conc), fungi, parasites
  • pH range 5-7 -> chlorine is most volatile
  • suppressed by the presence of organic materials
  • storing conditions: in dark, closed containers, low temp
  • DO NOT MIX: NH3, formaldehyde
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5
Q

Calcium hypochlorite

A
  • solid
  • CaHOCl + CaCl + Ca(OH)2–> chlorinated lime (bleach powder)
  • > white, greyish, chlorine smelling, crumbling, hydroscopic powder, active chlorine: 25-35%
  • use: 2% - virus, bacteria vegetative form/ 20% - spores
  • no effect against fungi and parasites
  • disinfection of wells, other water resources and surfaces
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6
Q

Kloramin-T / Toluol

A

◦ whitish powder with chlorine odor
◦ Active chloride: min.25%
◦ Effect: bactericide, virucide, High cc sporocide too,
- No effect against fungi and parasites

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7
Q

Sodium dichloro-isocyanurate (NaDCC or SDIC)

A

◦ colourless, water-soluble solid
◦ strong chlorine odour
◦ 1 tablet to 10l water
◦ Effect is 30sec, in the presence of organic/inorganic contamination too
◦ Effect: bactericide, virucide, High cc sporocid and fungicid too

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8
Q

Iodine based compounds

A

• Iodophores→ iodine + organic substrate (surface active materials) which contain also
◦ + phosphoric acid→ solubilising the iodine (detergent)
◦ +buffers→↓pH
◦ +polyvinyl-pyrolidine→ bind up to 30% of iodine
• Disinfection: Iodine released from complex→ oxidizes function groups of germs
• Iodine content of the commercially available iodofores: 0.5-1.7%
• dark brown -light yellow (depends on active iodine content)
• Surface friendly, powerful cleaning effect, pH3-4
• Iodophors: Iodine complexed with an organic substrate (Incosan-W, Wescodyne, Iosan)
‣ 3-5% destroys vegetative forms of G+ and G-germs/ 6-10% sporocide effect/ 10% fungicidal effect
• Povidone Iodine - Betadine (pavidone-iodine)

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9
Q

Iodine based compoundes Pros and Cons

A
  • advantage: Bactericidal, viricidal, and fungicidal
  • disadvantage: Occasional skin sensitivity, Partially inactivated by organic debris, Less residual activity than chlorhexidine, Poor sporicidal activity
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10
Q

Aldehydes

A
  • Efficient, broad spectrum
  • CHO- radicals → destroy cell wall
  • Germicidal
  • Formaldehyde
  • Formalin
  • Glutaraldehyde
  • Other aldehyde based disinfectants: paraformaldehyde, glioxal, lysoform etc.
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11
Q

Formaldehyde

A

◦ at room temp: characteristically stinky
◦ Excessively irritant
◦ suffocating, cough evoking
◦ colorless gas which attacks all mucosal membranes

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12
Q

Formalin

A
  • commercially available form of formaldehyde
  • 35-37% water solution of the gas that contains further 10% methylalcohol and contaminants (formic acid, acetone etc)
  • disinfection of surfaces
  • water solution
  • in form of gas
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13
Q

Disinfection with watery solution of formaldehyde (formalin)

A

◦ usual concentration: 1-6%
◦ Temp dependencies
‣ optimum: 30-35oC
‣ below 20oC quick decrease
‣ below 13oC no disinfection capacity
‣ over 35oC quick volatilization, quick decrease
◦ pH optimum: pH2.4-4.0
◦ organic materials do not hinder its disinfection efficiency
◦ concentrations: vegetative forms: 1-3%, spores: 6%, acid-fast: 6-10%, moulds: 5%, viruses: 3-5%

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14
Q

Disinfection with formaldehyde gas

A

◦ generation of gas from the watery solution:
‣ by heating
‣ by aerosol generators
‣ by oxidizing materials (e.g. potassium permanganate)
◦ microclimatic requirements:
‣ more than 20 oC is needed
‣ optimum humidity: 80-90%
◦ optimum gas concentration in the air: 0.1-0.2%
◦ WARNING: in 7-73% conc formaldehyde forms EXPLOSIVE MIXTURE WITH AIR!
◦ Formaldehyde gas can be neutralized with ammonium gas

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15
Q

Glutaraldehyde

A

◦ Light yellow, slightly acidic liquid (25% Glutaraldehyde + ethanol)
◦ Activation with base (opt.pH8), Stable for 2weeks
◦ 2% bactericid, sporocid, virucid, fungicid
◦ Not paraziticid!
◦ Not corrosive,
◦ Toxic Sodium bisulfitede activates

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16
Q

Other aldehyde based disinfectants

A
  • paraformaldehyde: white, crystallized, formaldehyde stinking powder, used for gas disinfection of smaller stables.
    ‣ For 1m3 of stable air
    • 10g of paraformaldehyde should be added to
    • 30ml of water
    • then first 0.1g sodium hydroxide and
    • Afterwards 20g potassium permanganate should be added to the solution
  • glioxal
  • lysoform etc.
17
Q

Hydrogen peroxide

A

◦ colorless, odorless, aggressive, mildly acidic liquid, which decomposes with high speed;
◦ due to its speedy decomposition and strong corrosive effects the pure form is not used for disinfection;
◦ tensids (surface active materials) stabilize and lessen the corrosive effect;
◦ these compounds might be used for disinfection of utensils in 3-10% conc.

18
Q

Peroxy-acids

A
  • combo of hydrogen-peroxide and several organic acids
  • > mostly formic and acetic acids
  • commercially available peroxy-acids also contains phosphoric-acid and stabilizers
19
Q

Peracetic-acid

A

◦ aggressive fluid with vinegar-like odour;
◦ widely used in food industry
◦ in production of SPF animals—> wide antimicrobial effect (at low concentration) :
—> vegetative form: 0.2%, fungicide + sporocid: 0.4%, coccidiotic: 0.4%
◦ quick decomposition after use - Liner disinfection
◦ over 30oC quick evaporation
◦ simultaneous use with alkalis is forbidden!

20
Q

Surfactants

A
  • surface active agents
  • water/alcohol solution of these compounds reduce the surface tension of liquid surfaces dirty with fatty/greasy materials
  • help to remove them
  • enhance the efficiency of other disinfectants
  • anion-active tensids
  • cation-active tensids
  • non-ionic tensids
  • ampho-tensids
  • anorganic acids
  • organic acids
  • alkalis
21
Q

Anion-active tensids

A

◦ alkyl benzene sulfonate, alkil - sulphates, alkan - sulphates, some soaps etc.;
◦ strong lipoid solvent capacity;
◦ no disinfectant capacity;
◦ Deactivates the cation active tensids!

22
Q

Cation-active tensids

A

◦ Cetil-trimethil-ammoniumbromide, benzalkoniumchloride etc.;
◦ Sterogenol, Bradophen-H, etc.;
◦ Substances with disinfection capacity over pH3;
◦ they reduce the surface-activity of cell membranes and increase the permeability
◦ hard water reduces their efficiency

23
Q

Non-ionic tensids

A

◦ TWEEN-80 is the most known tensid of the group
◦ in solutions they do not dissociate into ions;
◦ mild disinfection capacity;
◦ they are often used in combination with other disinfectants;

24
Q

Ampho-tenids

A
  • these compounds contains both acidic and alkalic groups in the molecule
  • in acidic surrounding they behave as cation-active tensids;
  • in basic surrounding they act as anionic-tensids
25
Q

Anorganic acids

A

◦ (nitric-, hydrochloric-, sulphuric-and phosphoric-acid);

◦ due to strong corrosive effect today are not used

26
Q

Organic acids

A
  • (formic-, lactic-, malonic-, glutaric-, propionic-acid)
  • they are used in combination with other disinfectants to obtain enhanced virucidic and sporocidic activity;
  • salts of the propionic-acid or its combination with fumaric-, sorbic-acid, mono- and diglicerides are used for disinfection of grains
27
Q

Alkalis

A

◦ disinfection is based on the strong alkalic pH they provide;
◦ Calcium hydroxide—> slaked lime - Whitewash
◦ sodium-, potassioum-hyroxide: were used by the dairy industry;
—> hot solution in 2-4% concentration: bactericide, virucide
—> in 6% concentration: sporocide
—> strong corrosive effects

28
Q

Gaseous disinfectants

A
  • at room temp in gas-state
  • ethylen-oxid
  • beta-proprionlactone
  • methyl-bromide
29
Q

Ethylen-oxid

A

◦ sweetish-ether like substance;
◦ boiling point at 10.70C;
◦ good penetration: paper, cellophane, plastic containers;
◦ MOA: it attacks the sulphohydril-, amino-, carboxyl- and hydryl-radicals of proteins;
◦ strong bactericide, sporocide, virucide effect;
◦ at 450mg/l conc it kills all microbes;
◦ labour safety considerations:
-> inflammable, explosive
-> inhalation: headache, nausea, mucosal irritation
-> agriculture: textile and other containers, feed

30
Q

Beta-propionlactone

A
  • used for gas-sterilisation

- poisonous inhalation

31
Q

Methyl-bromide

A
  • good insecticide

- min. 15oC, 300g/m3

Animal Hygiene final (14 decks)

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