View
220
Download
0
Category
Tags:
Preview:
Citation preview
Sterilization & DisinfectionChemical Agents
Hugh B. Fackrell
chemster.ppt
04/18/23
2
Sterilization & Disinfection
Definitions Bacterial Cell Death General characteristics Types of Chemical Agents Comparisons
04/18/23
3
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
04/18/23
4
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
04/18/23
5Definitions
Sanitize– Removal of pathogens from inanimate objects– Mechanical or chemical cleaning– need not sterilize of disinfect
Contamination– Presence of living microbes on object
04/18/23
6
Definitions
Infection– Presence of living multiplying microbes in host
tissues– often pathogenic
Preservation– Prevention of spoilage– Control of Contamination– Bacteriostatic
04/18/23
7
Bacterial Cell Death
Time (min)
Survivors
(log)
0
1
2
3
4
5 1 log decrease = 90% kill
1 log Death rate (D) varies with bacteriocide
D Time(min) to kill 90%
04/18/23
8
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
04/18/23
9
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
04/18/23
10
Types of Chemical Agents
Phenols Halogens Metal ions Alcohols Detergents Alkylating agents Ethylene Oxide Hydrogen peroxide
04/18/23
11
When in doubt about efficiency of a disinfectant
Get a laboratory test
04/18/23
12
Phenols
Mechanism of action– Rupture the cell membrane– Denature enzymes (protein)
Effective in presence of organic matter– blood, pus, feces, vomitus
Good environmental disinfectants
04/18/23
13
Phenols (examples)
Phenol– corrosive to skin– smell– 1% effective disinfectant
04/18/23
14
Cresols
– Methyl phenol– Phenyl-phenol (“Lysol”)
04/18/23
15
Chlorinated phenols
Hexachlorophene– Effective against Gm +ve– absorbed through skin– Toxic to infants if used often
Pentachlorophenol– more toxic than above
04/18/23
16
Halogens
Cholorine Iodine
04/18/23
17
Iodine
Applications– Skin antiseptic– Environmental disinfectant
Mode of Action – Iodination of Tyrosine
04/18/23
18
Iodine (cont)
Prepare fresh– Dark brown - active– Straw Yellow - inactive
Clean area first– organic matter reduces activity
04/18/23
19
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
04/18/23
20
Chlorine
Bacteriocide, fungicidal, virucidal– 2-10 ppm
Applications– disinfection of water, sewage etc
Mode of Action– Oxidizes proteins
Features– corrosive– smells
04/18/23
21
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
04/18/23
22
Metal Ions
Silver– 1% AgNO3 eye drops
– gonnorrheal neaonatal opthalmitis
Mercury– Hg Cl2 Skin antiseptic
– Mercurochrome
Copper, zinc– fungicide, algacide– pressure treated wood
04/18/23
23
Alcohols
Ethanol– 70-75% in water best– absolute less effective
Isopropanol– kills Mycobacterium
“Tincture of … “ alcohol used as the solvent for other ingredient
04/18/23
24
Detergents
Sanitize– soaps– neutral detergents
Disinfect– Anionic detergents– Cationic detergents
More effective with phenol Surface active
DO NOT MIX
04/18/23
25
Anionic Detergents
-ve charge salts of long chain alkyl or aryl sulphonates
04/18/23
26
Cationic Detergents + ve charge non toxic inactivated by proteins
– eg cotton fibres
effective at low concentrations Quaternary ammonium compounds
– Benzalkonium chloride– eg “Zephiran”
Not effective for
Pseudomonas
04/18/23
27
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
04/18/23
28
Alkylating Agents
Cross link proteins, nucleic acids– -NH2, -OH,-SH,-COOH
Formaldehyde Glutaraldehyde Beta-priopiolactone Ethylene oxide
04/18/23
29
Formaldehyde
HCHO Toxic Irritant Gas - fumigant Solutions- protein vaccines
– tetanus diptheria
04/18/23
30
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
04/18/23
31
Beta-propiolactone
Carcinogenic Unstable
– degrades but leaves no residue
Applications- sera, vaccines
04/18/23
32
Ethylene Oxide
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
H2C CH2
O
Pregnant women should not be exposed!!
04/18/23
33
Hydrogen Peroxide
Oxidizing agent Disinfectant -6%
– Bactericidal– Fungicidal– Virucidal
Prepare fresh
04/18/23
34
Kill curves of various antiseptics%
su
rviv
ors
Time (sec)
Soap & water
70% ethanol
Tincture of Merthiolate
Aqueous Zephiran
Tincture of Zephiran
Tincture of Iodine
Recommended