EXP 44 Chemical Agents of Control:
Disinfectants and Antiseptics
Part A: Disc Diffusion testing of Disinfectants and
Antiseptics
AGENTS (PART 1)
PHENOLIC COMPOUND
PHENOL
MECHANISMS
Germicidal effect caused by alteration of protein
structure resulting in protein denaturation.
Surface-active agent (surfactant) precipitates
cellular proteins and disrupts cell membranes.
USE
5% solution: disinfection.
0.5% to 1% solutions: Antiseptic effect and relief of itching as it exerts a local anesthetic effect on sensory nerve endings.
CRESOLS
MECHANISMS
Similar to phenol.
Poisonous and must be used externally.
50% solution of cresols in vegetable oil, known as
Lysol®.
USE
2% to 5% Lysol solutions used as
disinfectants.
hexachlorophene
MECHANISMS
Germicidal activity similar to phenol.
USE
reduction of pathogenic organisms on skin; added to detergents,soaps, lotions, and creams.
effective against gram-positive
organisms.
An antiseptic used topically.
resorcinol
MECHANISMS
Germicidal activity similar to that of phenol
Acts by precipitating cell protein.
USE
Antiseptic.
Keratolytic agent for softening or
dissolving keratin in epidermis.
hexylresorcinol
MECHANISMS
Germicidal activity similar to that of phenol
USE
treatment of worm infections.
urinary antiseptic.
thymol
MECHANISMS
related to the cresols.
more effective than phenol.
USE
Antifungal activity.
treatment of hookworm infections.
mouthwashes and gargle
solutions.
ALCOHOLS
ethyl
isopropyl
MECHANISMS
Lipid solvent.
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denaturation and coagulation of proteins.
Wetting agent used in tinctures to increase the wetting ability of other chemicals.
Germicidal activity increases with increasing molecular weight.
USE
Skin antiseptics:ethyl—50% to 70%.
isopropyl—60% to 70%.
HALOGENS
Chlorine compounds
Germicidal effect resulting from rapid
combination with proteins.
Chlorine reacts with water to form hypochlorous
acid, which is bactericidal.
oxidizing agent.
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non competitively inhibits enzymes, especially those dealing with glucose metabolism, by reacting with Sh and nh2 groups on the enzyme molecule.
USE
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Water purification.
Sanitation of utensils in dairy and restaurant industries.
Chloramine, 0.1% to 2% solutions, for wound irrigation and dressings.
microbicidal.
iodine compounds
MECHANISMS
mechanism of action is not entirely known, but it
is believed that it precipitates proteins.
Surface-active agent.
USE
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tinctures of iodine are used for skin antisepsis.
treatment of goiter.
effective against spores, fungi, and viruses.
AGEBTS PART 2
Heavy Metals
mercury compounds
inorganic
mercury bichloride
mercurial ointments
MECHANISMS
mercuric ion brings about precipitation of
cellular proteins.
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noncompetitive inhibition of specific enzymes caused by reaction with sulfhydryl group (Sh) on enzymes of bacterial cells.
USE
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inorganic mercurials are irritating to tissues, toxic systemically, adversely affected by organic matter, and incapable of acting on spores.
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mercury compounds are mainly used as disinfectants of laboratory materials.
organic
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mercurochrome
(merbromin)
merthiolate (thimerosal)
metaphen (nitromersol)
merbak (acetomeroctol)
mechanisms
Similar to those of inorganic mercurials, but in
proper concentrations are useful antiseptics.
much less irritating than inorganic mercurials.
use
Less toxic, less irritating; used
mainly for skin asepsis.
do not kill spores.
Silver compounds:
Silver nitrate
mechanisms
Precipitate cellular proteins.
interfere with metabolic activities of microbial
cells.
inorganic salts are germicidal.
use
Asepsis of mucous membrane of
throat and eyes.
Surface-active agents
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Wetting agents: emulsifiers, soaps, and detergents
mechanisms
Lower surface tension and aid in mechanical
removal of bacteria and soil.
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if active portion of the agent carries a negative electric charge, it is called an anionic surface active agent. if active portion of the agent carries a positive electric charge, it is called a cationic surface-active agent.
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exert bactericidal activity by interfering with or by depressing metabolic activities of microorganisms.
disrupt cell membranes
Alter cell permeability
use
Weak action against fungi, acid-fast
microorganisms, spores, and viruses
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Cationic agents: Quaternary ammonium compounds and Benzalkonium chloride
mechanisms
Lower surface tension because of keratolytic,
detergent, and emulsifying properties.
their germicidal activities are reduced by soaps.
use
Bactericidal, fungicidal; inactive
against spores and viruses.
Asepsis of intact skin.
disinfectant for operating-room
equipment.
dairy and restaurant sanitization.
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Anionic agents: tincture of green soap and Sodium tetradecyl sulfate
neutral or alkaline salts of high-molecular-weight
acids. Common soaps included in this group.
exert their maximum activity in an acid medium
and are most effective against gram-positive cell.
Same as all surface-active agents.
use
Cleansing agent.
Sclerosing agent in treatment of
varicose veins and internal hemorrhoids
Acids
Alkali
mechanisms
destruction of cell wall and cell membrane.
Coagulation of proteins.
disinfection; however, of little
practical value.
formaldehyde
Alkylating agent causes reduction of enzymes
use
room disinfection.
Alcoholic solution for instrument
disinfection.
Specimen preservation.
ethylene oxide
Alkylating agent causes reduction of enzymes
Sterilization of heat-labile material
B-Propiolactone
Alkylating agent causes reduction of enzymes
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Sterilization of tissue for grafting.
destruction of hepatitis virus.
room disinfection.
basic dyes:
Crystal violet
Affinity for nucleic acids; interfere with
reproduction in gram-positive organisms.
Skin antiseptic.
Laboratory isolation of gramnegative
bacteria.
EFFICIENCY
Concentration
Length of exposure
Type of microbial population to be
destroyed
Environmental conditions
Temperature
Type of material on which the
microorganisms exist
pH