Sterilization & Disinfection
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Transcript Sterilization & Disinfection
Sterilization & Disinfection
Chemical Agents
Hugh B. Fackrell
chemster.ppt
2
Sterilization & Disinfection
Definitions
Bacterial Cell Death
General characteristics
Types of Chemical Agents
Comparisons
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Definitions
Sterilization
– Complete Destruction of ALL microbes
Disinfection
– Killing of pathogens on inanimate objects
– physical or chemical
Antiseptic
– A chemical agent for disinfection of living
tissue
– External skin, mouth vagina
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Definitions
Bacteriocide
– kill microbes
– also germicide, fungicide, virucide
Bacteriostatic
– Prevents or stops microbial growth
– also fungistatic, virustatic
Aseptic(Asepsis)
– Prevent contamination of person or object by
microbes
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Definitions
Sanitize
– Removal of pathogens from inanimate objects
– Mechanical or chemical cleaning
– need not sterilize of disinfect
Contamination
– Presence of living microbes on object
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Definitions
Infection
– Presence of living multiplying microbes in host
tissues
– often pathogenic
Preservation
– Prevention of spoilage
– Control of Contamination
– Bacteriostatic
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Bacterial Cell Death
Survivors
(log)
1 log decrease = 90% kill
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1 log
Death rate (D) varies
with bacteriocide
4
3
2
1
D
0
Time (min)
Time(min) to
kill 90%
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Chemical agents
Wide variety in susceptibility
Growing cells more susceptible than resting
cells or spores
Gram +ve more susceptible than Gram -ve
Mycobacterium (TB) more resistant
Hepatitis virus very resistant
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General Rule for Disinfection
Clean then disinfect
– organic matter inactivates many chemicals
Use at recommended strength
– Undiluted NOT always best
– 70% alcohol better than 100% alcohol
Prevent contamination of disinfectant
Prepare fresh
– deterioration after prolonged storage
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Types of Chemical Agents
Phenols
Halogens
Metal ions
Alcohols
Detergents
Alkylating agents
Ethylene Oxide
Hydrogen peroxide
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When in doubt about efficiency
of a disinfectant
Get a laboratory test
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Phenols
Mechanism of action
– Rupture the cell membrane
– Denature enzymes (protein)
Effective in presence of organic matter
– blood, pus, feces, vomitus
Good environmental disinfectants
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Phenols (examples)
Phenol
– corrosive to skin
– smell
– 1% effective disinfectant
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Cresols
– Methyl phenol
– Phenyl-phenol (“Lysol”)
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Chlorinated phenols
Hexachlorophene
– Effective against Gm +ve
– absorbed through skin
– Toxic to infants if used often
Pentachlorophenol
– more toxic than above
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Halogens
Cholorine
Iodine
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Iodine
Applications
– Skin antiseptic
– Environmental disinfectant
Mode of Action
– Iodination of Tyrosine
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Iodine (cont)
Prepare fresh
– Dark brown - active
– Straw Yellow - inactive
Clean area first
– organic matter reduces activity
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Iodine Formulations
Tincture iodine I2 in ethanol
Aqueous iodine I2 in NaI/KI
Iodophors (organic)
– I2 in nonionic detergent
• Wesocdyne
– Generally 75 ppm
– Mycobacterium 450 ppm
– Iodoform
• I2 chemically combined
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Chlorine
Bacteriocide, fungicidal, virucidal
– 2-10 ppm
Applications
– disinfection of water, sewage etc
Mode of Action
– Oxidizes proteins
Features
– corrosive
– smells
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Chlorine /formulations
Chlorine gas
– Poisonous
– forms HOCl
(hypochlorous acid) in
water
Applications
– water supplies
– swimming pools
– sewage effluent
Inorganic chlorine
– Bleach NaOCl
– hypochlorite Ca(0Cl)2
– chloramine
effective against
– Hepatitis
– HIV
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Metal Ions
Silver
– 1% AgNO3 eye drops
– gonnorrheal neaonatal opthalmitis
Mercury
– Hg Cl2 Skin antiseptic
– Mercurochrome
Copper, zinc
– fungicide, algacide
– pressure treated wood
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Alcohols
Ethanol
– 70-75% in water best
– absolute less effective
Isopropanol
– kills Mycobacterium
“Tincture of … “ alcohol used as the solvent
for other ingredient
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Detergents
Sanitize
– soaps
– neutral detergents
Disinfect
– Anionic detergents
– Cationic detergents
DO NOT MIX
More effective with phenol
Surface active
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Anionic Detergents
-ve charge
salts of long chain alkyl or aryl sulphonates
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Cationic Detergents
+ ve charge
non toxic
Not effective for
Pseudomonas
inactivated by proteins
– eg cotton fibres
effective at low concentrations
Quaternary ammonium compounds
– Benzalkonium chloride
– eg “Zephiran”
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Chlorohexidine
“Hibitane”
– 4% gluconate
Emulsion used as a scrub
Topical application for minor skin infections
– inefficient at high concentrations
Mode of action
– cell membrane
– denatures protein
– not affected by organic matter
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Alkylating Agents
Cross link proteins, nucleic acids
– -NH2, -OH,-SH,-COOH
Formaldehyde
Glutaraldehyde
Beta-priopiolactone
Ethylene oxide
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Formaldehyde
HCHO
Toxic
Irritant
Gas - fumigant
Solutions- protein vaccines
– tetanus diptheria
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Glutaraldehyde
2% glutaraldehyde pH 8
Exposure time
– 5 min bactericidal
– 10 min kills Mycobacterium, Heptatitis virus
– 10 hr sterilizes
Applications
– Lensed instruments, tubing, scalpels, inhalators
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Beta-propiolactone
Carcinogenic
Unstable
– degrades but leaves no residue
Applications- sera, vaccines
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Ethylene Oxide
H2C
CH2
O
Sterilizes heat sensitive or chemcial
sensitive objects
Flammable, explosive carcinogenic
Gas sterilizing autoclave
– 3-4 hr, 60 oC, high pressure
– 24 hr room temperature to dissipate gas
– use with CO2 or FREON to reduce explosions
Pregnant women should not be exposed!! 4/13/2015
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Hydrogen Peroxide
Oxidizing agent
Disinfectant -6%
– Bactericidal
– Fungicidal
– Virucidal
Prepare fresh
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Kill curves of various antiseptics
% survivors
Soap & water
Tincture of
Merthiolate
Aqueous Zephiran
Tincture of
Iodine
Tincture of
Zephiran
Time (sec)
70% ethanol
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