Transcript 2ndDisinfection

Individual antimicrobial processes
Common sterilizers and disinfectants
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Sterilizers
– Physical
• Dry heat (> 160 oC)
• Most heat (>121 oC)
• Ionizing radiation
– Chemical
• Gaseous chemicals
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Disinfectants
– Physical
• Ultraviolet radiation
• Hydrostatic pressure
– Chemical
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Surface-active agents
Phenolic compounds
Iodine and iodine compounds
Peoxygen compounds
Chlorine species (free chlorine, chloramines)
Chlorine dioxide
Ozone
Sterilizers
Dry heat (I)
• Mechanism: protein denaturation, enzyme inhibition, and RNA and
DNA breakdown
• Protein coagulation (complete denaturation) (e.g. egg albumin)
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50 % water: 56oC
25 % water: 74-80oC
18 % water: 80-90oC
6 % water: 145oC
0 % water: 160-170oC
• Time-temperature in sterilization with dry air (to inactivate bacterial
spores)
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170oC for 60 min
160oC for 120 min
150oC for 150 min
140oC for 180 min
121oC for overnight
Dry heat (II)
• Advantages
– Deep penetration
– Less corrosivity
• Disadvantages
– High temperature
– Long sterilization period
– Deterioration of materials
• Used only for those materials that can not be
sterilized by moist heat: petroleum, oil, powders,
sharp instruments, and glassware
Moist heat (I)
• Mechanism: protein denaturation, enzyme
inhibition, RNA and DNA breakdown
• Advantage
– Low temperature and short sterilization period
(121oC for 15-30 min)
• Disadvantage
– Less penetration
– Moisture damage
Moist heat (II) (A steam autoclave)
Ionizing radiation (I)
• Electromagnetic radiations: γ radiation, xray, and electrons
• Particle radiations: α radiation, β radiation,
meson, positron, neutrino
• Mechanism: single or double-strand
breakage in DNA
Ionizing radiation (II)
Ionizing radiation (III)
Ionizing radiation (IV)
Ionizing radiation (V)
Ionizing radiation (VI)
Gaseous chemical sterilization (I)
• Alkylating agents (Alkylation of DNA)
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Ethylene oxide
Propylene oxide
Formaldehyde
Beta-propiolactone
• Oxidizing agents (Oxidation of proteins and
nucleic acids)
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Hydrogen peroxide
Peracetic acid
Chlorine dioxide
Ozone
Gaseous chemical sterilization (II)
Gaseous chemical sterilization (III)
(Chemical) disinfectants
Surface-active agents
• Amphiphilic compounds
• Anionic, cationic, nonionic, and amphoterics
• Cationic surfactants: Quaternary ammonium
compounds
– Basic structure:
• One nitrogen atom
• Four carbon atoms covalently linked to the nitrogen atom
• An anion eletrostatically linked to the nitrogen atom
– Mechanism: Protein denaturation, enzyme inhibition,
and disruption of cytoplasmic membrane
Quaternary ammonium compounds (I)
Quaternary ammonium compounds (II)
Quaternary ammonium compounds (III)
Quaternary ammonium compounds (III)
• Advantages
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Low toxicity
Low corrosivity
Stable at high temperature and wide pH range
Relatively tolerable with organic load
• Disadvantage
– Not effective against viruses, protozoa, and spores
– Less effective at low temperature
– Inhibited by most anionics and hard water salts
Quaternary ammonium compounds (IV)
(applications)
• General surface disinfectant
• Industrial application (hot water in large
commercial laundry)
• Swimming pool water??? Drinking water
(emergency situation)???
Phenol compounds (I)
• Structure
• Mechanism
– Bacteria: denaturation of proteins, inhibition of
enzymes, damages on plasma membrane
– Viruses and fungi: Unknown
Phenol compounds (II)
Phenol compounds (III)
Phenol compounds (IV)
• Advantages
– Effective against viruses, bacteria, and fungi
– Stable in concentrate
– Tolerable for organic load and hard water
• Disadvantages
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Not effective against spores
High toxicity
Not effective at low temperature
Incompatible with nonionic and cation surfactants
Phenol compounds (IV)
• General surface disinfectant
• Gemicidal soaps and lotions, antiseptics,
preservatives in cosmetics, and
mouthwash preparation (Listerine)
Iodine and iodine compounds (I)
• Chemistry
• Antimicrobial agents: I2 (free iodine), HOI
(hypoiodous acid), H2OI+ (Iodine cation)
• Mechanism: protien denaturation,
damages in plasma membrane, and
nucleic acid breakdown
Iodine and iodine compounds (II)
Iodine and iodine compounds (III)
• Advantage
– Effective against viruses, bacteria, fungi, protozoa
and bacterial/fungal spores
– Low toxicity
– Very stable in concentrate
• Disadvantages
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Chemical hazard (staining)
Less effective at low temperature
Relatively corrosive at high temperature
Expensive
Iodine and iodine compounds (IV)
Peroxygen compounds (I)
• Hydrogen peroxide, peracetic acids,
perfomic acid, and perpropionic acids
• Mechanism: hydroxyl radicals: proteins,
lipids, and DNA
• Very effective on most microbes including
spores
Peroxygen compounds (II)
Peroxygen compounds (III)
Peroxygen compounds (IV)
Peroxygen compounds (V)
Peroxygen compounds (VI)
• Advantages
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Strong, fast-acting
Effective against most microbes including spores
No toxicity
No environmental concern
Effective over wide pH (up to 7.5) and temperature ranges (40 oF
– 150 oF)
– Stable in concentrate
– Tolerable for organic load
• Disadvantages
– Limited stability at use solution
– Corrosive on soft surfaces (brass, copper, and mild and
galvanized steel)
Peroxygen compounds (VII)
• Excellent surface disinfectants
• Industrial water systems (Legionella
control)
• Wastewater disinfection
• Antiseptics
• Cold sterilization of phamatheuticals
(emulsions, hydrogels, ointments, and
powders)
To be continued