CHEMICAL CONTROL OF MICROORGANISMS. LEARNING OBJECTIVES LEARNING OBJECTIVES At the end of the topic, students will be able to; Differentiate between Sterilization.

CHEMICAL CONTROL OFCHEMICAL CONTROL OFMICROORGANISMSMICROORGANISMS

LEARNING OBJECTIVESLEARNING OBJECTIVES

At the end of the topic, students will be able to;At the end of the topic, students will be able to; Differentiate between Sterilization & Differentiate between Sterilization &

Disinfection.Disinfection. Differentiate between Antiseptics & Differentiate between Antiseptics &

Disinfectants.Disinfectants. List the properties of an ideal Disinfectant/ List the properties of an ideal Disinfectant/

Antiseptic.Antiseptic. Differentiate halogens used as antiseptics from Differentiate halogens used as antiseptics from

halogens used as disinfectants.halogens used as disinfectants. Identify the methods of action and preferred Identify the methods of action and preferred

uses of chemical disinfectants.uses of chemical disinfectants. Identify the appropriate uses for surface-active Identify the appropriate uses for surface-active

agents.agents.

DISINFECTION Disinfection is the elimination of pathogens, except spores, from inanimate objects.

Disinfectants are chemical agents used to clean inanimate objects.

If the object is lifeless such as table top, the chemical agent is known as DISINFECTANT. However, if the object is living, such as tissue of the human body, the chemical is an Antiseptic.

THE IDEAL DISIFECTANTTHE IDEAL DISIFECTANT

Must be able to kill microorganisms.Must be able to kill microorganisms. non-toxic to animals or humans esp. if used as non-toxic to animals or humans esp. if used as

antiseptic.antiseptic. Should be soluble in water.Should be soluble in water. Resistant to inactivation. Should be useful in very diluted form and perform its

job in a relatively short time. Stable. Penetrating. Not corrode instruments. Easy to obtain. Inexpensive.

CHEMICAL CONTROL OF MICROBIAL CHEMICAL CONTROL OF MICROBIAL AGENTSAGENTS

IMPORTANT IMPORTANT CHEMICALCHEMICAL AGENTS: AGENTS:

Halogens.Halogens. Phenol and phenolic compounds.Phenol and phenolic compounds. Heavy metals.Heavy metals. Alcohols.Alcohols.

OTHER CHEMICAL AGENTS:OTHER CHEMICAL AGENTS:

Formaldehyde.Formaldehyde. Glutaraldehyde.Glutaraldehyde. Ethylene oxide.Ethylene oxide. Beta propiolactone.Beta propiolactone. Hydrogen peroxide.Hydrogen peroxide. Soap and detergents.Soap and detergents. Dyes.Dyes. Acids.Acids.

HALOGENSHALOGENS

IodineIodine ChlorineChlorine

IODINEIODINE

One of the oldest and most effective One of the oldest and most effective germicidal agents.germicidal agents.

It inhibits protein synthesis and oxidizes –SH groups of amino acids.

Also Halogenates tyrosine in protein.

Tincture of IodineTincture of Iodine (2% I (2% I22+2% Na+2% Na22I in I in

70% alcohol) is a commonly used 70% alcohol) is a commonly used antiseptic for wounds.antiseptic for wounds.

Continue…Continue…

IODINEIODINE Iodine is also used in the form of a substance Iodine is also used in the form of a substance

known as known as IodophorsIodophors Iodophors are mixtures of iodine with surface Iodophors are mixtures of iodine with surface

active agents which acts as carriers and active agents which acts as carriers and solubilizers for the iodine. One of these agents solubilizers for the iodine. One of these agents is PVP (polyvinylpyrrolidone)is PVP (polyvinylpyrrolidone)

The complex can be expressed as PVP-I.The complex can be expressed as PVP-I. Iodine is released slowly from this complex and Iodine is released slowly from this complex and

thus reduce the irritation of the antiseptic.thus reduce the irritation of the antiseptic.

CHLORINECHLORINE

Most widely used disinfectants.Most widely used disinfectants.

Chlorine is powerful oxidizing agent that kills by Chlorine is powerful oxidizing agent that kills by cross-linking essential sulfhydryl groups in cross-linking essential sulfhydryl groups in enzymes to form the inactive sulfide.enzymes to form the inactive sulfide.

Used as a disinfectant to purify the water Used as a disinfectant to purify the water supply and to treat swimming pools , where it supply and to treat swimming pools , where it keeps bacterial populations at low levels.keeps bacterial populations at low levels.

Not sporicidal.Not sporicidal.

CHLORINECHLORINE

It is also the active component of hypochlorite, It is also the active component of hypochlorite, which is used as a disinfectant in home and which is used as a disinfectant in home and hospitals.hospitals.

Hypochlorite compounds release free chlorine Hypochlorite compounds release free chlorine in solution.in solution.

Sodium hypochloriteSodium hypochlorite (NaOCl) also known as (NaOCl) also known as Bleach.Bleach.

Calcium hypochloriteCalcium hypochlorite [Ca(OCl) [Ca(OCl)22] also known as ] also known as

Chlorinated lime.Chlorinated lime.

CHLORINECHLORINE

Cloramine,Cloramine, such as Chloramine-T, are organic such as Chloramine-T, are organic compounds that contain chlorine.compounds that contain chlorine.

These compounds release free chlorine more These compounds release free chlorine more slowly than hypochlorite sol. and are more slowly than hypochlorite sol. and are more stable.stable.

They are valuable for general wound They are valuable for general wound antiseptics and root canal therapy.antiseptics and root canal therapy.

PHENOL & PHENOLICSPHENOL & PHENOLICS

PHENOL & PHENOLIC COMPOUNDSPHENOL & PHENOLIC COMPOUNDS

Damage membrane, inactive enzymes, denature proteins.

Very effective disinfectants. A 5% aqueous solution of phenol rapidly kills

the vegetative cells of microorganisms BUT spores are much more resistant.

PHENOL & PHENOLIC COMPOUNDSPHENOL & PHENOLIC COMPOUNDS

Cresol (phenol derv.) have greater germicidal activity and lower toxicity than the parent compound.

Hexyl Resorcinol (another phenol derv.), is marketed in a solution of glycerin & water, used in mouth wash and topical antiseptic & in throat lozenges.

PHENOL & PHENOLIC COMPOUNDSPHENOL & PHENOLIC COMPOUNDS

Bisphenols… combination of two phenol molecules, are prominent in modern disinfection and antiseptics.Examples:

Orthophenylphenol e.g. is used in Lysol (a saponified cresol)

Hexachlorophene, was used extensively during the 1950s & 1960s in tooth paste, under arm deodorant and bath soap.

Chlorhexidine, 4% sol in isopropyl alcohol, used as a surgical scrub, hand wash and superficial skin wound cleanser.

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Chloroxylenol (Dettol)

A bisphenol in wide spread use is Trichlosan, a broad spectrum anti microbial agent, that destroys bacteria by disrupting cell membrane (& possibly, cell wall) by blocking the synthesis of lipids.

The chemical is included in antibacterial soaps, lotions, mouth washes, tooth pastes & kitchen sponges.

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PHENOL CO-EFFICIENTPHENOL CO-EFFICIENT Phenol has the additional distinction of being Phenol has the additional distinction of being

the standard against which other disinfectants the standard against which other disinfectants of a similar chemical structure are compared to of a similar chemical structure are compared to determine their antimicrobial activity.determine their antimicrobial activity.

PC is a number that indicates the disinfecting PC is a number that indicates the disinfecting ability of an antiseptic or disinfectant in ability of an antiseptic or disinfectant in comparison to phenol under identical comparison to phenol under identical conditions.conditions.

A PC higher than 1 indicates that the chemical A PC higher than 1 indicates that the chemical is more effective than phenol.is more effective than phenol.

PC less than 1 indicates poorer disinfecting PC less than 1 indicates poorer disinfecting ability than phenol.ability than phenol.

PC OF SOME COMMON PC OF SOME COMMON ANTISEPTICS & ANTISEPTICS & DISINFECTANTSDISINFECTANTSCHEMICAL CHEMICAL AGENTAGENT

StaphylococcStaphylococcus aureusus aureus

Salmonella Salmonella typhityphi

PhenolPhenol 1.01.0 1.01.0

Chloramine Chloramine 133.0133.0 100.0100.0

Tincture of Tincture of iodineiodine

6.36.3 5.85.8

Lysol Lysol 5.05.0 3.23.2

Mercury Mercury chloridechloride

100.0100.0 143.0143.0

Ethyl alcoholEthyl alcohol 6.36.3 6.36.3

Formalin Formalin 0.30.3 0.70.7

Hydrogen Hydrogen peroxideperoxide

-- 0.010.01

HEAVY METALSHEAVY METALS

Mercury, silver, copper.Mercury, silver, copper.Act by precipitation of proteins and Act by precipitation of proteins and

oxidation of sulfhydryl groups.oxidation of sulfhydryl groups.Bacteriostatic.Bacteriostatic.

MERCURYMERCURY Mercuric chlorideMercuric chloride For treating skin diseases.For treating skin diseases. V.toxic to the host.V.toxic to the host. Anti microbial activity of mercury is Anti microbial activity of mercury is

reduced when other organic matter is reduced when other organic matter is present.present.

THIMEROSAL (mercury derv.), previously THIMEROSAL (mercury derv.), previously used as a preservative in vaccine.used as a preservative in vaccine.

COPPERCOPPER Active against chlorophyll containing Active against chlorophyll containing

organisms.organisms. Potent inhibitor of algae.Potent inhibitor of algae. Copper sulfate, incorporated in to Copper sulfate, incorporated in to

algicides and is used in swimming pools algicides and is used in swimming pools and municipal water supplies.and municipal water supplies.

CuSOCuSO44 is also mixed with lime to form the is also mixed with lime to form the

bluish-white Bordeaux mixture used since bluish-white Bordeaux mixture used since 1882, to control the growth of fungi.1882, to control the growth of fungi.

SILVERSILVER Silver nitrateSilver nitrate Skin antiseptic.Skin antiseptic. 1% AgNO3 solution may be placed in the 1% AgNO3 solution may be placed in the

eyes of newborns to protect against eyes of newborns to protect against infection by infection by Neisseria gonorrhoeaeNeisseria gonorrhoeae..

Silver sulfadiazine is used to prevent Silver sulfadiazine is used to prevent infections by burn wounds.infections by burn wounds.

INFECTED EYE OF NEW BORN BY INFECTED EYE OF NEW BORN BY Neisseria gonorrhoeaeNeisseria gonorrhoeae..

ALCOHOLALCOHOL

ALCOHOLSALCOHOLS Mode of action: Alcohols dehydrate cells, Mode of action: Alcohols dehydrate cells,

disrupt membranes and cause disrupt membranes and cause coagulation of protein.coagulation of protein.

Examples: Ethyl alcohol, isopropyl alcohol Examples: Ethyl alcohol, isopropyl alcohol and methyl alcoholand methyl alcohol

Application: A 70% aqueous solution is Application: A 70% aqueous solution is more effective at killing microbes than more effective at killing microbes than absolute alcohols. absolute alcohols.

70% ethyl alcohol (spirit) is used as 70% ethyl alcohol (spirit) is used as antiseptic on skinantiseptic on skin..

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Propyl & IPA in conc. ranging from 40-80% are Propyl & IPA in conc. ranging from 40-80% are bactericidal for vegetative cells.bactericidal for vegetative cells.

IPA or rubbing alcohol, has high bactericidal IPA or rubbing alcohol, has high bactericidal activity in conc. as high as 99%activity in conc. as high as 99%

used to disinfect clinical thermometers.used to disinfect clinical thermometers.

Methyl alcohol is less bactericidal than ethyl Methyl alcohol is less bactericidal than ethyl alcohol. alcohol.

Methyl alcohol kills fungal spores, hence is Methyl alcohol kills fungal spores, hence is useful in useful in disinfecting inoculation hoods.disinfecting inoculation hoods.

Methyl alcohol is toxic to tissues and is used Methyl alcohol is toxic to tissues and is used infrequently.infrequently.

Methyl alcohol is highly poisonous, even the Methyl alcohol is highly poisonous, even the fumes of this compound may produce fumes of this compound may produce permanent injury to the eyes.permanent injury to the eyes.

ALDEHYDEALDEHYDE

FORMALDEHYDEFORMALDEHYDE GLUTARALDEHYDEGLUTARALDEHYDE

FORMALDEHYDEFORMALDEHYDE HCHOHCHO Reacts with functional group in proteins & Reacts with functional group in proteins &

nucleic acids.nucleic acids. FORMALIN: 37% solution in water.FORMALIN: 37% solution in water. In Microbiology, formalin is used for In Microbiology, formalin is used for

inactivating viruses in certain vaccinesinactivating viruses in certain vaccines..Continue…Continue…

In gaseous form, formaldehyde is expelled into In gaseous form, formaldehyde is expelled into a closed chamber where it is a a closed chamber where it is a sterilizing agentsterilizing agent for surgical equipments, hospital gowns & for surgical equipments, hospital gowns & medical instruments.medical instruments.

Penetration is poor and the surface must be Penetration is poor and the surface must be exposed to the gas for up to 12 hrs for effective exposed to the gas for up to 12 hrs for effective sterilization.sterilization.

Formaldehyde leaves a residue, and Formaldehyde leaves a residue, and instruments must be rinsed before use.instruments must be rinsed before use.

GLUTARALDEHYDEGLUTARALDEHYDE Reacts with functional group in proteins & Reacts with functional group in proteins &

nucleic acids.nucleic acids. 2% sol. of this chemical (Cidex) exhibits a wide 2% sol. of this chemical (Cidex) exhibits a wide

spectrum of antimicrobial activity.spectrum of antimicrobial activity. Effective against vegetative bacteria, fungi, Effective against vegetative bacteria, fungi,

bacterial & fungal spores and viruses.bacterial & fungal spores and viruses. Glutaraldehyde is 10 times more effective than Glutaraldehyde is 10 times more effective than

formaldehyde & is less toxic.formaldehyde & is less toxic. For sterilizing urological instruments, For sterilizing urological instruments,

respiratory therapy equipments & other special respiratory therapy equipments & other special equipments.equipments.

ETHYLENE OXIDEETHYLENE OXIDE Mode of action: It is an alkylating agent. Mode of action: It is an alkylating agent. It acts by alkylating sulfydryl-, amino-, carboxyl- It acts by alkylating sulfydryl-, amino-, carboxyl-

and hydroxyl- groups.and hydroxyl- groups. EtO is liquid at temp below 10.8EtO is liquid at temp below 10.8ooC. Above this C. Above this

temp. , it vaporizes rapidly.temp. , it vaporizes rapidly. Excellent penetration capacity & sporicidal Excellent penetration capacity & sporicidal

activity.activity. Toxic & highly explosive.Toxic & highly explosive. Since it is highly flammable, it is Since it is highly flammable, it is usually usually

combined with COcombined with CO22 (10% CO (10% CO22+ 90% EO)+ 90% EO)

Continue…Continue…

ETHYLENE OXIDEETHYLENE OXIDE

It is an effective sterilizing agent for heat & It is an effective sterilizing agent for heat & moisture sensitive materials.moisture sensitive materials.

EtO is used to sterilize papers, leather, wood, EtO is used to sterilize papers, leather, wood, metal and rubber products as well as plastics.metal and rubber products as well as plastics.

In hospitals, it is used to sterilize catheters, In hospitals, it is used to sterilize catheters, artificial heart valves, heart-lung machine artificial heart valves, heart-lung machine components & other optical equipment.components & other optical equipment.

ETHYLENE OXIDEETHYLENE OXIDE

BETA-PROPIOLACTONEBETA-PROPIOLACTONE

It is an alkylating agent and acts through It is an alkylating agent and acts through alkylation of carboxyl- and hydroxyl- groups.alkylation of carboxyl- and hydroxyl- groups.

It is a colorless liquid with pungent to slightly It is a colorless liquid with pungent to slightly sweetish smell. sweetish smell.

It is an effective sporicidal agent, and has It is an effective sporicidal agent, and has broad-spectrum activity.broad-spectrum activity.

0.2% is used to sterilize biological products.0.2% is used to sterilize biological products. It is used to sterilize vaccines, sera & surgical It is used to sterilize vaccines, sera & surgical

instruments.instruments. Disadvantages: It has poor penetrating power Disadvantages: It has poor penetrating power

and is a carcinogen.and is a carcinogen.

HYDROGEN PEROXIDEHYDROGEN PEROXIDE

It is an oxidizing agent that attacks sulfhydryl It is an oxidizing agent that attacks sulfhydryl groups, thereby inhibiting enzymatic activity.groups, thereby inhibiting enzymatic activity.

Used as antiseptic to clean wounds.Used as antiseptic to clean wounds. Used to disinfect contact lenses.Used to disinfect contact lenses. Its effectiveness is limited Its effectiveness is limited because bacteria and

body tissues contain enzymes (catalase) that inactivate hydrogen peroxide.

Sterilization can also be achieved after 6 hrs of Sterilization can also be achieved after 6 hrs of exposure to a 6% solution.exposure to a 6% solution.

SOAPS AND DETERGENTSSOAPS AND DETERGENTS A soap is a chemical compound of fatty acids A soap is a chemical compound of fatty acids

combined with potassium or hydrogen combined with potassium or hydrogen peroxide.peroxide.

The pH of the compound is usually about 8.0 & The pH of the compound is usually about 8.0 & some microbial destruction is therefore due to some microbial destruction is therefore due to the alkaline conditions established on the skin.the alkaline conditions established on the skin.

However, the major activity of the soap is as a However, the major activity of the soap is as a de-germing agent for the mechanical removal de-germing agent for the mechanical removal of m.org. from the skin surface.of m.org. from the skin surface.

Soaps are ‘wetting agents’, i.e. they emulsify & Soaps are ‘wetting agents’, i.e. they emulsify & solubilize particles clinging to a surface.solubilize particles clinging to a surface.

Detergents are synthetic chemicals acting as Detergents are synthetic chemicals acting as strong wetting agent & surface tension strong wetting agent & surface tension reducers.reducers.

While soaps are always negatively charged, some detergents are negatively charged while others are positively charged.

One example of a positively charged detergent are quaternary ammonium compounds (also known as quats)

QUATS Quats are cationic detergents that act by

disrupting lipid bilayers.

MOAMOA They have the property of concentrating They have the property of concentrating

at interfaces between lipid containing at interfaces between lipid containing membrane of bacterial cell and membrane of bacterial cell and surrounding aqueous medium. surrounding aqueous medium.

These compounds have long chain These compounds have long chain hydrocarbons that are fat soluble and hydrocarbons that are fat soluble and charged ions that are water-soluble. charged ions that are water-soluble. Since they contain both of these, they Since they contain both of these, they concentrate on the surface of concentrate on the surface of membranes. They disrupt membrane membranes. They disrupt membrane resulting in leakage of cell constituents.resulting in leakage of cell constituents.

QUATS

Bacteriostatic. Quats are most effective against Gram-positive

bacteria Quats do not kill endospores, Mycobacteria

spp., nor non-enveloped viruses Zephiran Benzalkonium chloride Cepacol Cetylpyridinium chloride

USES: As sanitizing agents for industrial

equipment & food utensils. as skin antiseptics. in mouth washes. storage solution for contact lenses. For disinfecting hospital walls & floors.

DYESDYES

TRIPHENYLMETHANE DYESTRIPHENYLMETHANE DYES:: Crystal violetCrystal violet Malachite greenMalachite green ACRIDINE DYESACRIDINE DYES:: AcriflavineAcriflavine ProflavineProflavine

TRIPHENYLMETHANE DYESTRIPHENYLMETHANE DYES

As antiseptic against species of Bacillus & As antiseptic against species of Bacillus & Staphylococcus.Staphylococcus.

As Gentian violet for trench mouth & for As Gentian violet for trench mouth & for Candida albicansCandida albicans infection such as thrush. infection such as thrush.

MOA: interferes with the cell wall construction.MOA: interferes with the cell wall construction. The dye is bactericidal at very weak dilutions of The dye is bactericidal at very weak dilutions of

less than 1:10,000less than 1:10,000

ACRIDINE DYESACRIDINE DYES

ACRIFLAVINE AND PROFLAVINE.ACRIFLAVINE AND PROFLAVINE. Used as antiseptics for staphylococcal infection Used as antiseptics for staphylococcal infection

in wounds.in wounds. Bactericidal Bactericidal MOA: interact with bacterial nucleic acidMOA: interact with bacterial nucleic acid

ACIDSACIDS

Benzoic acidBenzoic acid Salicylic acidSalicylic acid Organic acids are particularly Organic acids are particularly

valuable as food preservative.valuable as food preservative. Lactic & acetic acid e.g. are important Lactic & acetic acid e.g. are important

preservatives in sour foods such as preservatives in sour foods such as cheese & pickled products.cheese & pickled products.

Propionic acid is added to bakery Propionic acid is added to bakery products to keep microbial population products to keep microbial population low.low.