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Chemical Agents in Microbial Control

Chemical Agents In Microbial Control

by ebarber6, Nov. 2014

Subjects: MICROBIOLOGY - Lecture 10 - Nov. 24

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78 Cards in this Set

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	The Ideal Chemical Agent	Fast-acting in low concentrations Stable in the presence of organic substances Broad-spectrum microbicidal action Non-toxic to humans and other animals
	The Ideal Chemical Agent	Penetrability – non-destructive, non-corrosive, non-staining Easy to prepare and stable once prepared Inexpensive and readily available Odorless or pleasant odor
	The Ideal Chemical Agent	Compatible with soaps and detergents Residual effect on treated surfaces Stable to moderate pH and temperature changes
	Antimicrobial Chemicals	Occur in liquid, gaseous or solid state Gaseous and solid chemicals often dissolved in water or alcohol for ease of use Pure water as solvent = aqueous Alcohol or alcohol-water as solvent = tinctures
	Antimicrobial Chemicals Factors	- population size - population composition - duration of exposure - local environment - concentration of the chemical agent - temperature - organic matter
	Levels of Chemical Decontamination High Level Disinfectant	*Kill endospores Sterilents when used properly Used on medical devices that cannot be sterilized with heat and are meant to enter body tissues - critical item (breach membrane)
	Levels of Chemical Decontamination Intermediate Level Disinfectant	Kill fungal spores, resistant pathogens such as TB, and viruses Used on respiratory equipment/thermometers Items that come in contact with mucous membranes but do not penetrate - semi-critical items
	Levels of Chemical Decontamination Low Level Disinfectant	Eliminate only vegetative bacteria, vegetative fungal cells and some viruses Used to clean electrodes, furniture, surfaces, etc. Items that touch skin surfaces but not mucous membranes - non-critical items
	Evaluation of Disinfectant Use-Dilution Test	Test effectiveness of disinfectant Microbes used: S. aureus, S. enterica, P. aeruginosa Contaminated surface exposed to disinfectant
	Evaluation of Disinfectant Use-Dilution Test	After contact time, disinfectant neutralized and surface incubated Good disinfectant = no re-growth
	Evaluation of Disinfectant Disk-Diffusion Test	Filter paper disk impregnated with chemical disinfectant or antiseptic Placed on agar plate
	Evaluation of Disinfectant Disk-Diffusion Test: Zone of Inhibition	Inhibition is variable and dependent upon: - Growth medium (agar) used - Microbial load - Concentration of chemical used - Incubation conditions: time, temperature, atmospheric condition
	Commonly Used Chemicals	- alcohols - chlorine compounds - iodine compounds - glutaraldehyde - peroxides - ethylene oxide
	Commonly Used Chemicals Alcohol	Ethyl and isopropyl alcohol used Act by denaturing proteins, dissolving membrane lipids - OPTIMUM CONCENTRATION 70%; range 50-90% - Must be combined with water in order to penetrate organisms
	Commonly Used Chemicals Alcohol	Effective against vegetative cells including TB and some viruses Intermediate level disinfectant – used on skin prior to injections; used to disinfect thermometers
	Commonly Used Chemicals Alcohol	Advantages: - Unaffected by the presence of organic matter - Stable and easily handled - No residue
	Commonly Used Chemicals Alcohol	Disadvantages: - Ineffective against spores or Hep B - Flammable
	Commonly Used Chemicals Halogen Compounds	Reactive non-metallic elements; strong oxidizing agents Act on amino acids and enzymes (proteins)
	Commonly Used Chemicals Halogen Compounds	Activity affected by: - concentration - temperature - pH Class includes chlorine and iodine compounds
	Commonly Used Chemicals Halogen Compounds: Chlorine	Hypochlorite (hypochlorous acid) 1% solution kills vegetative cells, endospores, fungi and viruses
	Commonly Used Chemicals Halogen Compounds: Chlorine	Active chemical in regular household bleach Strong oxidizing agent inhibits cellular enzyme function
	Commonly Used Chemicals Halogen Compounds: Chlorine	Advantages: - Inexpensive - Good deodorant (smells clean) - Readily available
	Commonly Used Chemicals Halogen Compounds: Chlorine	Disadvantages: - Corrosive - Relatively unstable - Aggravating to the skin
	Commonly Used Chemicals Halogen Compounds: Chlorine	Disadvantages: - Ineffective at alkaline pH - Activity reduced by organic matter - Irritating odor and residue
	Commonly Used Chemicals Iodine Compounds	Effective against vegetative bacteria, viruses, fungi and amoebae Act slowly against endospores
	Commonly Used Chemicals Iodine Compounds	Inactivated by organic material Thought to combine with amino acids of enzymes and other cellular proteins
	Commonly Used Chemicals Iodine Compounds	Tincture: 2% iodine, 70% alcohol solution acts a skin antiseptic Disadvantages: - staining; solution brown in colour - irritating odor/residue - toxic if ingested - can cause allergic reaction
	Commonly Used Chemicals Iodine Compounds	Usually only used by old school doctors; most doctors dont like because of number of disadvantages; benefit of colour is that you can see where have already cleaned
	Commonly Used Chemicals Iodine Compounds	Iodine mixed with surface active agent from which iodine is released slowly - Increases degree of penetration Used as surgical scrub and for pre-surgical tissue preparation - Wescodyne, Povidone-Iodine, Betidine (3% - 5%)
	Commonly Used Chemicals Iodine Compounds Iodophors	Advantages: - water soluble - less prone to staining/irritating - non-allergenic - non-corrosive
	Commonly Used Chemicals Iodine Compounds Phenolics	Used as antiseptics on the skin - hexachlorophene - chlorhexidene Denature proteins and disrupts the cell membrane
	Commonly Used Chemicals Iodine Compounds Phenolics	Kill vegetative cells and some fungi Moderately effective against spores
	Commonly Used Chemicals Iodine Compounds Phenolics	Advantages: - Stable to heating & drying - Unaffected by organic compounds - Non-irritating to the skin - Leaves a residual protective film
	Commonly Used Chemicals Iodine Compounds Phenolics	Disadvantages: - Slight odor - Expensive - Corrosive
	Commonly Used Chemicals Iodine Compounds Phenolics: Hexachlorophene	Esp. effective against Gram positives Retains activity when mixed with soaps and detergents - low concentration - bacteriostatic (inhibits) - high concentration - bactericidal (kills)
	Commonly Used Chemicals Iodine Compounds Phenolics: Hexachlorophene	Absorbed into bloodstream – can cause neurological damage 3% concentration available by prescription only
	Commonly Used Chemicals Iodine Compounds Phenolics: Chlorhexidene	Contains chlorine and phenolic rings - 6 sided carbon that has a hydroxyl group Effective against gram positives, negatives and fungi Targets cell membrane to decrease surface tension and causes protein denaturation
	Commonly Used Chemicals Iodine Compounds Phenolics: Chlorhexidene	Effects less deleterious than hexachlorophene - much more popular in hospital setting (safe) Milder, low toxicity, rapid action, not absorbed into deeper tissues Used in antibacterial mouthwash to treat periodontal disease
	Commonly Used Chemicals Iodine Compounds Phenolics: Chlorhexidene	Mixed with detergent, a common surgical scrub - Strong affinity for binding to the skin or mucous membranes Not absorbed into the bloodstream
	Commonly Used Chemicals Iodine Compounds Phenolics: Chlorhexidene	Ventilator Associated Pneumonia: - pneumonia secondary to mech vent - reason: trach tube down throat makes them unable to control upper airway allowing what normally would be coughed out to slip down into lower resp tract - as secretion strickle down into lungs, develop pneumonia
	Commonly Used Chemicals Iodine Compounds Phenolics: Chlorhexidene	- mouth is most highly contaminated area in body - use antibacterial mouthwash due to high level of microbes in mouth to minimize how many get down into airways
	Commonly Used Chemicals Glutaraldehyde	Yellow acidic liquid with a mild odor Reacts with amino groups to inactivate critical enzymes 2% solution, e.g., Cidex, Metricide
	Commonly Used Chemicals Glutaraldehyde	Less irritating to the skin and eyes than formaldehyde Must be contained in fume hood
	Commonly Used Chemicals Glutaraldehyde *very important slide	Most useful as an immersion disinfectant - Intermediate unless able to leave for 3 hours Requires activation – solution then stable for ~3 weeks
	Commonly Used Chemicals Glutaraldehyde *very important slide	Cold sterilent when items immersed for long periods – kills endospores after 3 hours of immersion - dental equipment - respiratory equipment - fiberoptic endoscopes - medical devices not compatible with heat
	Commonly Used Chemicals Glutaraldehyde	Advantages: - Active in the presence of organic matter - Non-corrosive; does not damage plastics - Broad spectrum activity
	Commonly Used Chemicals Glutaraldehyde	Disadvantages: - Somewhat unstable - Long turnaround as prolonged exposure may be necessary - Irritating to tissues; Can be toxic
	Commonly Used Chemicals Quaternary Ammonium Compounds	Cationic (+ve charge) surface-active agents → ↓ surface tension - enzyme inhibition - protein denaturation - damage cell membraines
	Commonly Used Chemicals Quaternary Ammonium Compounds	Enzyme inhibition, protein denaturation and disruption of cell membranes Used at concentrations of 0.1% to 0.2%
	Commonly Used Chemicals Quaternary Ammonium Compounds	Used for disinfecting surfaces (floors and walls); some used as antiseptics Destroy a variety of vegetative bacteria, including staph, TB and enveloped viruses Not effective against endospores or Hepatitis B
	Commonly Used Chemicals Quaternary Ammonium Compounds	Little activity against resistant Pseudomonas aeruginosa Naked virus more resistance - protein subunits of the capsomere a lot of chemicals attack envelope
	Commonly Used Chemicals Quaternary Ammonium Compounds	Advantages: - stable in presence of organic compounds - easy to handle - non-irritating - no residue
	Commonly Used Chemicals Quaternary Ammonium Compounds	Disadvantages: - Detergents can interfere with activity - Corrosive - Low concentrations can support bacterial growth
	Commonly Used Chemicals Peroxides	Oxidizing agent which inactivate essential protein
	Commonly Used Chemicals Peroxides	Hydrogen peroxide: - 3% antiseptic solution - Cleansing of surface and deep wounds - Releases oxygen destroys anaerobic bacteria - Some sporicidal activity - As a disinfectant, used at concentrations from 6% to 25%
	Commonly Used Chemicals Peroxides	Zinc peroxide: used in irrigation of deep wounds Benzoyl peroxide: used for deep wounds - in acne medications
	Commonly Used Chemicals Ethylene Oxide	Colourless, flammable gas Boiling point 10.8°C, relative humidity 33% Concentration of gas usually 850 mg/L (min. 450 mg/L)
	Commonly Used Chemicals Ethylene Oxide	Blocks microbial enzyme activity and prevents DNA replication (**SETS APART FROM REST) Diluted in inert gas to eliminate the danger of explosion - Carboxide 10%, Oxyfume 20%
	Commonly Used Chemicals Ethylene Oxide	Articles must be cleaned and packaged Material must be permeable to heat and moisture Articles must be aerated with medical air for several hours to allow dissipation of residual absorbed gas
	Commonly Used Chemicals Ethylene Oxide	Chemical and biological controls used for sterility testing Used for heat-sensitive medical and dental equipment - ex: rubber gloves, catheters, electronic instruments
	Commonly Used Chemicals Ethylene Oxide	Excellent penetrating power, destroying all organisms –sterilent!
	Commonly Used Chemicals Ethylene Oxide	BUT: - direct contact can damage mucous membranes - rated as a carcinogen - slow acting (90 min - 12 hours to process - depending on population) - long turnaround time (4 hours to aerate)
	Commonly Used Chemicals Chlorine Dioxide	Another gas used as a sterilent Strong alkylating agent – causes protein denaturation
	Commonly Used Chemicals Chlorine Dioxide	Effective against: - vegetative bacteria - fungi - viruses - endospores
	Commonly Used Chemicals Chlorine Dioxide	Uses: Treat drinking water, wastewater, food-processing equipment, medical waste Decontaminated the Senate offices in the U.S. after the anthrax attack (2001)
	Comparison of Sterilization Methods Dry Heat Sterilization – Hot Air Oven	160°C for 2 hours or 170°C for 1 hour Biological indicator – Bacillus subtilis - Incubate at 37°C (body temp)
	Comparison of Sterilization Methods Dry Heat Sterilization – Hot Air Oven	Packaging of materials… - Must not insulate from heat - Must not be destroyed by temperatures used - Paper bags, muslin, aluminum foil, trays and pans are acceptable - Plastic bags and containers are unacceptable
	Comparison of Sterilization Methods Dry Heat Sterilization – Hot Air Oven	Advantages: - Effective and safe forserilization of metal instruments - Does not dull cutting edges - Does not rust/corrode
	Comparison of Sterilization Methods Dry Heat Sterilization – Hot Air Oven	Disadvantages: - Long cycle time required for sterilization - Poor penetration - May discolour or char fabric - Destroys heat-labile items
	Comparison of Sterilization Methods Moist Heat Sterilization - The Autoclave	121°C at 15 psi (above normal) for 15-20 minutes OR 132°C at 30 psi (above normal) for 5 minutes Biological indicator – Bacillus stearothermophilus - Incubate at 56°C
	Comparison of Sterilization Methods Moist Heat Sterilization - The Autoclave	Packaging of materials: - Must allow steam to penetrate - Paper, surgical muslin, certain plastics are acceptable - Closed glass or metal containers are unacceptable
	Comparison of Sterilization Methods Moist Heat Sterilization - The Autoclave	Advantages: - Short cycle time - Good penetration - Wide range of materials can be sterilized - Variety of cycles for different materials
	Comparison of Sterilization Methods Moist Heat Sterilization - The Autoclave	Disadvantages: - Corrode unprotected carbon steel instruments - Dulling of unprotected cutting edges - Packages can remain wet at end of cycle - Can destroy heat-sensitive materials
	Comparison of Sterilization Methods Chemical Sterilizer - Ethylene Oxide	20°C to 25°C at 33% relative humidity, time varies depending on item Biological indicator – Bacillus subtilis - Incubate at 37°C
	Comparison of Sterilization Methods Chemical Sterilizer - Ethylene Oxide	Packaging of materials: - Must allow penetration of gas - Paper and plastic bags are acceptable - Sealed metal or glass containers are unacceptable
	Comparison of Sterilization Methods Chemical Sterilizer - Ethylene Oxide	Advantages: - High capacity for penetration - Does not damage heat sensitive materials - Evaporates without leaving a residue (hours) - Suitable for materials damaged by moisture
	Comparison of Sterilization Methods Chemical Sterilizer - Ethylene Oxide	Disadvantages: Very long turn around time Retained in liquids and rubber materials for a long time Causes tissue irritation if not well aerated
	Comparison of Sterilization Methods Chemical Sterilizer - Ethylene Oxide	Disadvantages: Risk of explosion More expensive

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