Disinfectants a ppt

DISINFECTANTS

Review

• Bacterial growth is increase in cell numbers

• Growth depends on temperature, pH, osmotic pressure, oxygen, and nutrients

• Log phase cultures are most sensitive to growth inhibition

Bacteria Undergo

Exponential Growth

Growth measurements: direct

• Plate counts– detect viable organisms

• Direct microscopic counts– detect total numbers

Growth measurements: Indirect• Turbidity

– light absorption compared to a standard

• Metabolic activity– amount of product produced in a given

time

• Dry weight– remove water and weigh

• Principles of effective disinfection– Concentration of disinfectant– Organic matter– pH– Time

• Often chemical methods are compared to Phenol. If more effective given a phenol coefficient of >1. If less effective give a phenol coefficient of <1.

Chemical Methods of Microbial Control

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Chemical Antimicrobials• Potency

• Phenol coefficient

• Filter paper method

• Use dilution test

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Disinfectant Selection Criteria• Time of action

• Safety

• Microbe range

• Penetration

• Preparation

• Cost

• Odor

• Bacterial populations die at a constant logarithmic rate.

Mechanisms of action for Antimicrobial control agent

• Alternation of membrane permeability• Damage to proteins• Damage to nucleic acids• Interfere with metabolic pathways

Actions of Microbial Control Agents

Methods may be Physical or Chemical

•Physical like heat

•Chemical like disinfectants

• Number of microbes

• Environment (organic matter, temperature, biofilms)

• Time of exposure• Microbial

characteristics

• Condition of microbes - lag, log or sport

Effectiveness of antimicrobial treatment depends on:

Figure 7.1b

Chemical Methods of Microbial Control

Figure 7.6

Evaluating a disinfectantDisk-diffusion method

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Mechanisms of Action• Protein damage

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Mechanisms of Action

• Membrane damage

• Other

Terminology

• Sterilization: destruction of all forms of microbial life

• Commercial sterilization: sufficient heat to kill Clostridium botulinum endospores (some non-pathogenic thermophilic bacteria may survive)

• Disinfection: destruction of vegetative pathogens on inert substances

Terminology• Antisepsis: chemical destruction of

vegetative pathogens on living tissue• Degerming: mechanical removal of

microbes from limited area• Sanitization: lowering microbial counts

on eating and drinking utensils to safe levels

Terminology

• Biocide or germicide: kills microorganisms

• Fungicide: kills fungi

• Virocide: inactivates viruses

• Bacteriostatic agent: stops growth of bacteria

Terminology

• Sepsis: bacterial contamination

• Asepsis: absence of significant contamination

• Aseptic technique minimizes contamination

Microbial Death• Microbes die at a constant rate• Factors affecting how long it takes to kill

bacteria– number of microbes– environment

• slowed by organic materials, biofilms• hastened by heat

Microbial Death• Factors affecting how long it takes to kill

bacteria– time of exposure– characteristics of microbes: most resistant

are• spores• thick lipid coats• protozoan cysts

Actions of Microbial Control Agents

• Alteration of membrane permeability

• Damage to proteins and nucleic acids

• Mutation

Physical Control Methods

• Temperature

• Desiccation

• Osmotic pressure

• Radiation

Heat

• Must know temperature and time needed to kill critical bacteria

• Moist heat - boiling, autoclave

• Dry heat - oven

Moist Heat

• Coagulates proteins by breaking hydrogen bonds

• Boiling: 10 minutes kills most pathogens (hepatitis virus needs 30 minutes and spores need 20 hours!)

• Autoclave: 15 psi for 15 minutes (121° C)

Autoclave

Pasteurization• Used when taste of product would be

damaged by longer heating: lowers numbers of pathogens (63°C for 30 minutes)

• High-temperature short-term (HTST) pasteurization (72°C for 15 seconds)

• UHT: sterilization (140°C for 3 seconds)

Dry Heat

• Flaming

• Oven (170°C 2 hours)

Low Temperature

• Refrigeration is bacteriostatic– Most pathogens do not grow– Exception?

• Freezing: slow freezing creates ice crystals

Membrane Filtration

• Pore size controls which microbes are removed

• HEPA filters used in safety hoods and operating theaters

Limiting Water

• Desiccation : bacteriostatic– lyophilization used to preserve cultures

• Osmotic pressure – high concentrations of salt or sugar

• Molds and yeasts most resistant

Radiation

Radiation

• Ionizing radiation: gamma rays, X rays, high energy electron beams – most energetic

• Ionization of H2O to form OH- radicals --> mutations and death

• Low level ionizing radiation used on spices, certain meats and vegetables

• High energy electron beams used for medical supplies

UV Radiation

• Thymine dimers in DNA

• Germicidal lamps, vaccine disinfection

• Not penetrating

• Can damage eyes

Microwaves

• Very little effect on microbes

• Microwave ovens kill vegetative pathogens by heating

• Solid foods heat unevenly

Chemical Methods• Disinfectants and antiseptics

• Surface-active agents (surfactants)

• Chemical food preservatives

• Aldehydes

• Gas sterilization

• Oxidizing agents

• [Antibiotics]

Microbial Sensitivity

to Chemical Biocides

A tribute to Ignaz Semmelweis

Ames Test

EAGLE H. SPAULDING BELIEVED THAT HOW AN OBJECT WILL BE DISINFECTED DEPENDED ON THE OBJECT’S INTENDED USE

SPAULDING CLASSIFICATION

• The system is based on the patient's risk for infection that various types of instrument or equipment contact can create.

Low Level Disinfection

• 3% Hydrogen Peroxide (10 Minutes) or 0.5% AHP (5 minutes)

• – 60-95% Alcohol (10 minutes)• – Hypochlorite (1000 ppm)• – QUAT• – Iodophors

High Level Disinfection

• 2% glutaraldehyde (20 minutes)

• – 6% Hydrogen Peroxide (30 Minutes) or 7% AHP (30 Minutes)

• – Pasteurization (30 minutes @ 75°C

• – 0.2% Peracetic acid (30-45 Minutes)

Putting it together

• Client comes to spa for manicure and

pedicure

• • How do we clean the chairs?

• • How do we clean the equipment?

• Patient comes to MD office for annual

• physical including PAP

• • What needs cleaning?

• • What Classification?

• • What Level?

Dentist Office

• Client attends clinic for extraction and 2

• fillings – requires xray study for impacted wisdom teeth

• Type of equipment used?

• Level of processing required?

Home Care Visit

• Visit assigned to client in home who requires vital sign check, glucose check, wound care and chest assessment

• What Classification of equipment would

you be using?• What level of processing is required?• What products do you have on hand?

Tattoo Palor

Antiseptics versus Disinfectants

Antiseptics: Use on skin and mucous membranes to kill

microorganisms Not for use on inanimate objects

Disinfectants: Use to kill microorganisms on inanimate objects Not for use on skin or mucous membranes High-level versus low-level disinfectants

Disinfectants

• Kill/inhibit growth of microbes on surfaces

• Phenols and phenolics: damage lipid membranes

– Active in presence of organic matter

– Stable

– Persist for long periods after application

PHENOLICS

• Examples: Benzyl-4-chlorophenol, Amyl phenol, Phenyl phenol

• Advantages and disadvantages: good general purpose disinfectants, not readily inactivated

• by organic matter, active against wide range of organisms (including mycobacterium), but not sporicidal.

Amphyl

• Dilutable, phenol-based cleaner is an effective germicidal, fungicidal, virucidal & tuberculocidal agent on hard, nonporous surfaces. Prevents growth of mold & mildew & their odors. Sanitizes laundry, linens, blankets & cloth diapers. Use on floors, walls, equipment, bed frames, bathroom fixtures, wheelchairs & more !

Figure 7.7

Phenol Phenolics. LysolBisphenols. Hexachlorophene, Triclosan

Disrupt plasma membranes

Disinfectants

• Halogens: iodine and chlorine– Iodine used in solution : Betadine® and

Isodine®– Chlorine is a gas that forms bleach

(hypochlorite) in water– Chloramines are chlorine and ammonia

Hypochlorite's

• They have a broad spectrum of antimicrobial activity, are unaffected by water hardness, are inexpensive and fast acting, and have a low incidence of serious toxicity

Hypochlorite's

• Hypochlorites are the most widely used of the chlorine disinfectants and are available in a liquid (e.g. sodium hypochlorite) or solid (e.g. calcium hypochlorite, sodium dichloroisocyanurate) form. The most common chlorine products in are aqueous solutions of 4 to 6% sodium hypochlorite, which are readily available as “household bleach”.

Antiseptics

• Biguanides: Chlorhexidine– Low toxicity– Used on skin and mucous membranes

Chlorhexidine

Antiseptics

• Biguanides: Chlorhexidine

• Low toxicity

–Used on skin and mucous membranes

Although chlorhexidine is effective in the presence of blood, soap, and pus, its activity is reduced

IODOPHORE AND TINCTURE

Iodine And Iodophor Disinfectants

• These compounds have been incorporated in time release formulations and in soaps (surgical scrubs). Simple iodine tinctures (dissolved in alcohol) have limited cleaning ability. These compounds are bactericidal, sporicidal, virucidal and fungicidal but require a prolonged contact time.

Iodine And Iodophor Disinfectants

• The disinfective ability of iodine, like chlorine, is neutralized in the presence of organic material and hence frequent applications are needed for thorough disinfection. Iodine tinctures can be very irritating to tissues, can stain fabric and be corrosive.

Providone Iodine

• was discovered in 1893 by the Swiss Karl Wilhelm von Nägeli as a toxic effect of metal ions on living cells, algae, molds, spores, fungus, virus, prokaryotic and eukaryotic microorganisms, even in relatively low concentrations. This antimicrobial effect is shown by ions of: mercury, silver, copper, iron,

lead, zinc, bismuth, gold, aluminium and other metals.

Heavy Metals

• Denature proteins– silver nitrate (topical cream)– mercuric chloride (paint)– copper sulfate (algaecide)– zinc (mouthwash, paints)

oligodynamic effect

Greek: oligos = few, Greek: dynamis = force)

Burns and Wounds

Mercurochrome

Dyes

Antiseptics

• Alcohol : protein denaturation and membrane damage– evaporate quickly– ethanol and isopropanol– [not effective if taken internally]

Alcohols

Antiseptics

• Alcohol : protein denaturation and membrane damage– evaporate quickly– ethanol and

isopropanol– [not effective if taken

internally]

Surfactants

• Decrease surface tension

• Soaps and detergents– Quaternary ammonium compounds :

microbicidal

Soap, Water and common sense are yet the best antiseptics

William Osler

Hydrogen Peroxide

• Stabilized hydrogen peroxides can be used to disinfect environmental surfaces. The literature contains several accounts of the properties, germicidal effectiveness, and potential uses for stabilized hydrogen peroxide in the hospital setting

Hydrogen Peroxide

• Stabilized peroxides may also be blended with iodophors or quaternary ammonia. Hydrogen peroxide is also blended with paracetic acid in high concentrations for use as a high-level disinfectant

Aldehydes

• Formaldehyde (formalin) and glutaraldehyde– Disinfect instruments– Used to preserve tissues for pathology– Cross-link protein molecules

Gluteraldehyde

• Aldehydes have a wide germicidal spectrum. Gluteraldehydes are bactericidal, virucidal, fungicidal, sporicidal and parasiticidal. They are used as a disinfectant or sterilant in both liquid and gaseous forms. They have moderate residual activity and are effective in the presence of limited amounts of organic material

Formaldehyde

• Formaldehyde is used as a disinfectant and sterilant both in the liquid and gaseous states. Formaldehyde is sold and used principally as a water-based solution called formalin, which is 37% formaldehyde by weight. The aqueous solution is bactericidal, tuberculocidal, fungicidal, virucidal and sporicidal

Oxidizing Agents

• Ozone

• Hydrogen peroxide

• Benzoyl peroxide

• Peracetic acid– Interfere with metabolism (especially of

anaerobes)

Per acetic Acid

• Peracetic, or peroxyacetic, acid is characterized by a very rapid action against all microorganisms. A special advantage of peracetic acid is it has no harmful decomposition products (i.e., acetic acid, water, oxygen, hydrogen peroxide) and leaves no residue. It remains effective in the presence of organic matter and is sporicidal even at low temperatures

Per acetic Acid

• It is used in automated machines to chemically sterilize medical, surgical, and dental instruments (e.g., endoscopes, arthroscopes).

Per acetic acid and hydrogen peroxide useful in Hemodialyzers

• Findings demonstrated that this product inactivated all microorganisms with the exception of bacterial spores within 20 minutes. The combination of per acetic acid and hydrogen peroxide has been used for disinfecting hem dialyzers.

Quaternary Ammonium Compounds

• The quaternaries are good cleaning agents but high water hardness and materials such as cotton and gauze pads may make them less microbiocidal because these materials absorb the active ingredients. As with several other disinfectants (e.g., phenolics, iodophors) gram-negative bacteria have been found to survive or grow in these preparations

Hard Surface Disinfectant

Gas Sterilization

• Ethylene oxide– Denatures proteins– Kills all spores and microbes with lengthy

exposure– High penetration

Microbial Characteristics and Microbial Control

Chemical agent Effectiveness against

Endospores Mycobacteria

Phenolics Poor Good

Quats None None

Chlorines Fair Fair

Alcohols Poor Good

Glutaraldehyde Fair Good

Antiseptic Effectiveness