MMG Physical Control
Terms
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decontamination
sterilization -
+ inhibiting or limiting microbial growth
+ elimination of all viable microbes -
disinfection
disinfectants -
+ elimination of microbes on inanimate objects, usually via chemical means
+ not necessarily sterilized -
sanitation
anitseptic -
+ reduction of microbial numbers on fomites
+ chemical agent that kills or inhibits microbes externally on body -
cidal
lytic -
+ kills microbes
- bacteriocidal
- fungicidal
- viricidal
+ kills by lysing cells
- bacteriolytic
- fungilytic -
static
antibiotic -
+ reversibly inhibits growth;
- bacteriostatic
- fungistatic
- viristatic
+ chemical produced by microbe that can kill or inhibit another microbe. Naturally occurring - chemotherapeutic agent
- + antimicrobial agent used internally to kill or inhibit a microbe; can be an antibiotic or chemically synthesized
- Microbe death rate
-
- die at constant death rate
- rate varies by organism and conditions
- most susceptible cells die first
- must use antimicrobial agent until even hardier cells are dead. - Effectiveness of antimicrobial agents
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- High-level: kills all pathogens including endospores
- Intermediate-level: kills fungal spores, protozoan cysts, viruses and pathogenic bacteria
- Low-level: kills vegetative bacteria, fungi, protozoa, and some viruses -
External Control Methods
Internal Control Methods -
+ External:
- Physical
- Chemical
+ Internal:
- Chemotherapeutic agents
- antibiotics - Most susceptible to most resistant cells
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- Enveloped viruses
- Gram-positive bacteria
- Nonenveloped viruses
- Fungi
- Gram-negative bacteria
- Active stage protozoa
- Cysts of protozoa
- Mycotobacteria
- Bacterial endospores - Physical methods of Microbial Control
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Moist heat; Dry heat; Refrigeration; Freezing;
Desiccation; Lyophilization;
Filtration; Osmotic pressure;
Ionizing radiation;
Nonionizing radiation - Types of Moist Heat (physical control)
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- Boiling
- Autoclaving
- Pasteurization
- Ultra-high temperature sterilization - Types of Dry Heat (physical control)
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- Hot air
- Incineration - Desiccation
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- Drying
- Conditions vary w/amount of water to be removed
- Inhibits metabolism
- Preserves food - Lyophilization
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- Freeze drying
- Minus 196 degrees for a few minutes while drying
- Inhibits metabolism
- Long term storage of bacterial cultures - Purpose of filtration
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- Separates microbes from air and liquids
- Sterilization of air and heat-sensitive ophthalmic and enzymatic solutions, vaccines, and antibiotics - Osmotic pressure (physical control)
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- Exposure to hypertonic solutions
- Inhibits metabolism
- Used to preserve food - Ionizing radiation (physical control)
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- Electron beams; gamma rays; x-rays
- Seconds to hours of exposure
- Destroys DNA
- Used to sterilize equipment and preserve food - Nonionizing radiation (physical control)
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- Ultraviolet light
- Irradiation w/260nm wavelength
- Inhibits DNA transcription and replication via formation of thymine dimers
- Used to disinfect/sterilize surfaces and transparent fluids/gases - Most widely used method of sterilization
-
- Moist Heat
- Dry Heat - Which is more efficient? Moist heat or dry heat?
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- Moist
- steam heat (autoclave)
- high temps melts cellular membranes and denatures proteins
- efficacy depends on time/temp - How is dry heat applied?
-
- In a type of oven
- requires 160-180 degrees C for 1-2 hours
- only items not effected: metals; glass; powders; oils - Pasteurization (physical control)
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- used for milk; ice cream; yogurt; fruit juices
- NOT sterilization; heat-tolerant and thermophilic microbes survive - What can filtration methods not block?
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- Viruses can pass through
- Not totally sterile
- Depth filters block larger particles
- Membrane filters block various sizes
- Nucleopore filters filter down to almost viral size - Antimicrobial agent
-
- natural or synthetic chemical
- selective toxicity - Minimum inhibitory concentration (MIC)
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- smallest amount of antimicrobial agent needed to inhibit growth of organism
- usually performed w/tube dilution; looking for no growth; confirm w/viable cell count - Agar diffusion
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- test various concentrations of antimicrobial agent
- diffuses outward from disc creating a zone of inhibition
- antibiotic may not diffuse in the chosen growth medium! -
Disinfectant
Antiseptics -
+ acts against surface microbes on inanimate objects
- dangerous if used parenterally
+ antimicrobial agents that are sufficiently non-toxic to tissues - Are disinfectants and antiseptics "specific" in their action against cells?
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- they are non-specific
- disrupt cell membranes
- alter proteins irreversibly - Chemical Controls
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- Disinfectants and Antiseptics
- Phenol; Phenolics; Alcohols; Halogens; Oxidizing agents; Surfactents; Heavy metals; Aldehydes; Gaseous agents; Antimicrobials - Phenol (chemical control)
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- Carbolic acid
- Denatures proteins and disrupts cell membranes
- was a surgical antiseptic - Phenolics (chemical control)
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- altered Phenol (biphenols)
- Denature proteins and disrupts cell membranes
- Disinfectants and antiseptics - Alcohols (chemical control)
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- Denatures proteins and disrupts cell membranes
- Disinfectants, antiseptics, and a solvent in tinctures - Halogens (chemical control)
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- Presumably denature proteins
- Disinfectants
- antiseptics
- water purification - Oxidizing agents
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- Peroxides, ozone, peracetic acid
- Denatures proteins
- Disinfectants; deep wound antiseptics; water purification; sterilization of equipment - Surfactants (chemical control)
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- Decrease surface tension of water
- Disrupt cell membranes
- soaps: degerming; detergents; antiseptic - Heavy Metals (chemical control)
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- Arsenic; zinc; mercury; silver; copper; etc
- Denatures proteins
- Fungistats in paint, creams, surgical dressings; catheters; algicide - Aldehydes (chemical control)
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- Glutaraldehyde and Formaldehyde
- Denatures proteins
- Disinfectant and embalming fluid - Gaseous agents (chemical control)
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- ethlyene oxide
propylene oxide
beta-propiolactone
- Denatures proteins
- Sterilizes heat and water sensitive objects - Antimicrobials (chemical control)
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- Act against cell walls, membranes, protein synthesis, and DNA transcription and replication
- Disinfectants and treatment of infectious diseases - Characteristics of Phenol
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- denatures proteins
- one of the first disinfectants
- Too caustic by itself
- Phenol substitutes are used: hexachlorophene; Lysol; amphil; staphene - Characteristics of Alcohols
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- Denatures proteins and disrupts cell membranes
- ethyl and isopropyl
- most effective as 70% solution
- effective against enveloped viruses, but not spores - Types and use of Halogens
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- iodine, chlorine, bromine, fluorine
- used to treat water - Behavior of Surfactants
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- reduce surface tension of solvents to make them more effective
- helps soap remove oil & microbes
- used in detergents: amphipathic - Types and use of Oxidizing Agents
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- Peroxides, ozono, peracetic acids
- kill by oxidation of microbial enzymes
- Peroxide disinfects surfaces
- Ozone treats water
- Peracetic acid is a sporacide used to sterilize equipment - Behavior and uses of Heavy Metals
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- Alter the 3D shape of proteins
- Silver nitrate can prevent blindness
- Thimerosal (mercury) used to preserve vaccines
- Copper controls algae growth (interferes with chlorophyll) - Uses of Aldehydes
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- Denature proteins and inactivates nucleic acids
- Formalin (37% solution for formaldehyde in water) used for embalming and disinfection