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47 Cards in this Set

  • Front
  • Back

+ inhibiting or limiting microbial growth

+ elimination of all viable microbes

+ elimination of microbes on inanimate objects, usually via chemical means

+ not necessarily sterilized

+ reduction of microbial numbers on fomites

+ chemical agent that kills or inhibits microbes externally on body

+ kills microbes
- bacteriocidal
- fungicidal
- viricidal

+ kills by lysing cells
- bacteriolytic
- fungilytic

+ 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
- 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
- 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
Moist heat; Dry heat; Refrigeration; Freezing;
Desiccation; Lyophilization;
Filtration; Osmotic pressure;
Ionizing radiation;
Nonionizing radiation
Types of Moist Heat (physical control)
- Boiling
- Autoclaving
- Pasteurization
- Ultra-high temperature sterilization
Types of Dry Heat (physical control)
- Hot air
- Incineration
- Drying
- Conditions vary w/amount of water to be removed
- Inhibits metabolism
- Preserves food
- Freeze drying
- Minus 196 degrees for a few minutes while drying
- Inhibits metabolism
- Long term storage of bacterial cultures
Purpose of filtration
- Separates microbes from air and liquids
- Sterilization of air and heat-sensitive ophthalmic and enzymatic solutions, vaccines, and antibiotics
Osmotic pressure (physical control)
- Exposure to hypertonic solutions
- Inhibits metabolism
- Used to preserve food
Ionizing radiation (physical control)
- Electron beams; gamma rays; x-rays
- Seconds to hours of exposure
- Destroys DNA
- Used to sterilize equipment and preserve food
Nonionizing radiation (physical control)
- 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?
- 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)
- used for milk; ice cream; yogurt; fruit juices
- NOT sterilization; heat-tolerant and thermophilic microbes survive
What can filtration methods not block?
- 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)
- 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
- test various concentrations of antimicrobial agent
- diffuses outward from disc creating a zone of inhibition
- antibiotic may not diffuse in the chosen growth medium!

+ 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?
- they are non-specific
- disrupt cell membranes
- alter proteins irreversibly
Chemical Controls
- Disinfectants and Antiseptics
- Phenol; Phenolics; Alcohols; Halogens; Oxidizing agents; Surfactents; Heavy metals; Aldehydes; Gaseous agents; Antimicrobials
Phenol (chemical control)
- Carbolic acid
- Denatures proteins and disrupts cell membranes
- was a surgical antiseptic
Phenolics (chemical control)
- altered Phenol (biphenols)
- Denature proteins and disrupts cell membranes
- Disinfectants and antiseptics
Alcohols (chemical control)
- Denatures proteins and disrupts cell membranes
- Disinfectants, antiseptics, and a solvent in tinctures
Halogens (chemical control)
- Presumably denature proteins
- Disinfectants
- antiseptics
- water purification
Oxidizing agents
- Peroxides, ozone, peracetic acid
- Denatures proteins
- Disinfectants; deep wound antiseptics; water purification; sterilization of equipment
Surfactants (chemical control)
- Decrease surface tension of water
- Disrupt cell membranes
- soaps: degerming; detergents; antiseptic
Heavy Metals (chemical control)
- Arsenic; zinc; mercury; silver; copper; etc
- Denatures proteins
- Fungistats in paint, creams, surgical dressings; catheters; algicide
Aldehydes (chemical control)
- Glutaraldehyde and Formaldehyde
- Denatures proteins
- Disinfectant and embalming fluid
Gaseous agents (chemical control)
- ethlyene oxide
propylene oxide
- Denatures proteins
- Sterilizes heat and water sensitive objects
Antimicrobials (chemical control)
- Act against cell walls, membranes, protein synthesis, and DNA transcription and replication
- Disinfectants and treatment of infectious diseases
Characteristics of Phenol
- denatures proteins
- one of the first disinfectants
- Too caustic by itself
- Phenol substitutes are used: hexachlorophene; Lysol; amphil; staphene
Characteristics of Alcohols
- 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
- iodine, chlorine, bromine, fluorine
- used to treat water
Behavior of Surfactants
- 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
- 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
- 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
- Denature proteins and inactivates nucleic acids
- Formalin (37% solution for formaldehyde in water) used for embalming and disinfection