Chapter 9 Learning Outcomes Flashcards
Sterilization
Removal or destruction of ALL microbes, including viruses and bacterial endospores, in or on an object. (To eradicate harmful microorganisms and viruses)
ex (Preparation of microbiological culture media and canned food)
Disinfection
Use of physical or chemical agents known as disinfectants (ultraviolet light, heat, alcohol, and bleach), to inhibit or destroy microorganisms, especially pathogens. Does not remove all… and only on inanimate objects.
ex (Use of phenolics, alcohols, aldehydes, or soaps on equipment)
Antisepsis
When a chemical, antiseptic, is used on skin or other tissue. It is a lower concentration but is similar to disinfectant.
ex (when giving a shot and cleaning skin with an alcohol swab)
Degerming
The removal of microbes from a surface by scrubbing.
ex (wash hands, nurse prepares arm for injection)
Sanitization
Process of disinfecting places and utensils used by the public to reduce the number of pathogenic microbes to meet accepted public health standards.
ex (washing tableware in scalding water in restaurants)
Pasteurization
Heat kills pathogens and reduces the number of spoilage microorganisms in food and beverages.
ex (Pasteurized milk and fruit juices)
Compare the effects of static/stasis versus cidal/cide control agents on microbial growth.
-static: a chemical or physical agent INHIBITS microbial metabolism and growth but does not kill microbes (refrigerator)
-cidal: Agents that DESTROY or permanently inactivate a particular type of microbe. (germicides)
Define microbial death rate and describe its significance in microbial control.
Microbial Death: The permanent loss of reproductive ability under ideal environmental conditions.
Significance: A broth becomes sterile when all the cells are dead. Die logarithmically
aseptic
free from contamination from viruses/bacteria/fung
Describe how antimicrobial agents act against cell walls, cytoplasmic membranes and nucleic acids.
Cell walls: Prevents cell wall from stopping the cell from bursting when osmosis occurs.
Cytoplasmic membranes: Allows cellular contents to leak out with causes the cell to die.
Proteins: Causes proteins shape to change by breaking the hydrogen and disulfide bonds which denatures the protein.
Nucleic Acids: Destroys nucleic acids which will produce fatal mutations.
List factors to consider in selecting a microbial control method.
- Site to be treated
- Relative susceptibility of Microorganisms
- Environmental Conditions
Identify the three most resistant groups of microbes and explain why they are
resistant to many antimicrobial agents.
- Bacterial endospores: Endospores of Bacillus and Clostridium can survive environmental extremes of temperature, acidity, and dryness.
- Species of mycobacteria: Cell walls contain a large amount of a waxy lipid which allows them to survive drying and protects them from most water-based chemicals.
- Cysts of protozoa: Cyst’s wall prevents entry of most disinfectants, protects against drying, and shields against radiation and heat.
Discuss the environmental conditions that can influence the effectiveness of
antimicrobial agents.
Temperature and pH. Higher temperatures cause chemicals to react faster and acidic conditions enhance the antimicrobial effect of heat
List and describe the five types of physical methods. Be sure to know the mode of
action and the representative uses of each physical method.
- Exposure of the microbes to extremes of heat and cold
- Desiccation
- Filtration
- Osmotic pressure
- Radiation
Heat related methods: Discuss the advantages and disadvantages of using moist
heat in an autoclave and dry heat in an oven for sterilization
*moist heat in an autoclave
-moist heat(commonly used to disinfect, sanitize, sterilize, and pasteurize) kills cells by denaturing proteins and destroying cytoplasmic membranes
-more effective in microbial control than dry heat bc water is a better conductor of heat than air
-The disadvantage is it takes longer for large volumes of liquids or solids bc it takes more time for heat to penetrate
*dry heat in an oven
-used for substances such as powders and oils that cannot be sterilized by boiling or w/ steam or for materials that can be damaged by repeated exposure to steam
-effective bc it denatures proteins and fosters the oxidation of metabolic and structural chemicals
-The disadvantage is it requires higher temps for longer times than moist heat bc dry heat penetrates more slowly
Explain the uses of Bacillus endospores in sterilization techniques.
Used to test if something is sterile or not. The endospores are impregnated into tape with is aseptically inoculated into sterile broth. If no growth appears, the original material is sterile.
Explain the importance of pasteurization and describe three different pasteurization
methods
Used to destroy microorganisms and pathogens in liquids that cause spoilage.
1. Batch Method: 63”C for 30 min.
2. Flash Pasteurization: 72”C for 15 second
3. Ultra-high-temperature Pasteurization: 135”C for 1 second
Refrigeration and Freezing: Describe the use and importance of refrigeration and
freezing in limiting microbial growth. Is refrigeration bactericidal or bacteriostatic?
Slow down chemical reactions and decrease microbial metabolism, growth, and reproduction.
Refrigeration: halts the growth of most pathogens.
Freezing: slow freezing (ice crystals puncture cell membranes) are more efficient than quick freezing.
Desiccation and Lyophilization: Compare and contrast desiccation and lyophilization.
Are these methods bactericidal or bacteriostatic?
Desiccation - Drying inhibits growth because of the removal of water. (drying)
Lyophilization- combines freezing and drying and is used for the long-term preservation of microbial cultures. (freeze-drying)
bacteriostatic
Filtration: Describe the use of filters for disinfection and sterilization.
Filters have pores that allow smaller particles to pass through while trapping and separating larger microbes The particles it is designed to trap are cells or viruses. Scientist can use this to estimate the number of microbes by comparing the viruses trapped to the volume passed through the filter.
Osmotic Pressure: Discuss the use of hypertonic solutions in microbial control
Enzymes are fully functional only in aqueous environments; therefore, removing water from osmotic pressure inhibits bacteria’s cellular metabolism.
Radiation: Differentiate ionizing radiation from nonionizing radiation as they relate
to microbial control. Can they achieve sterilization, disinfection, or both?
ionizing: shorter than 1nm in wavelength
electron beams, gamma rays, some xrays
ions disrupt hydrogen bonding and oxidize double covalent bonds and create hydroxyl radicals
non-ionizing: wavelength greater than 1nm
excites electrons, causing them to make new covalent bonds affects 3D structure of proteins and nucleic acids
Chemical Methods: Compare and contrast nine major types of antimicrobial chemicals and discuss the positive and negative aspects of each. Be sure to know the mode of action and the representative uses of each physical method.
- phenols: Denatures proteins and disrupts cell membranes (middle to low)
- alcohols: Denature proteins and disrupt cell membranes (middle)
- halogens: denature proteins (middle)
- oxidizing agents: denature proteins by oxidation (High)
- surfactants: Decrease surface tension of water and disrupt cell membranes (Low)
- heavy metals: Denature proteins (Low)
- aldehydes: denature proteins (High)
- gaseous agents: denature proteins (High)
- enzymes: denature proteins (High against target substrate)
Phenol and Phenolic: Distinguish between phenol and the types of phenolics and
discuss their action as antimicrobial agents
Phenol (carbolic acid) - Denatures proteins and
disrupts cell membranes
Uses: Original surgical antiseptic; now
replaced by less odorous and injurious
phenolics
Phenolics (chemically altered phenol; bis phenolics are composed of a pair of linked phenolics) - Denature proteins and disrupt cell membranes.
Uses: Disinfectants and antiseptics
