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59 Cards in this Set
- Front
- Back
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Who developed the growth curve?
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Buchanan
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What is generation time?
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Time required for a cell to divide or a population of cells to double
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When is the generation time most accurately calculated?
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During the Logarithmic Growth Phase
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What are the phases of the Growth Curve?
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1. Initial stationary phase
2. Lag phase 3. Logarithmic Growth Phase (Log Phase) 4. Maximum stationary phase 5. Logarithmic death phase |
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Describe the initial stationary phase
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-Adjustment of bacteria to the new environment
-Few cells die due to osmotic shock |
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Describe the lag phase
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-Lag in reproduction/cell division
-Cells are still viable and metabolically very active (make enzymes) -Cells increase in size (4x/6x the normal size) -Cells are getting ready to divide |
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Describe the logarithmic growth phase
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-Max metabolism
-Max cell division -Cell size becomes normal -Shortest generation time is found here -Staining becomes most effective here |
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What is the generation time of E. coli, Staphylococcus aureus, and Mycobacterium leprae during the logarithmic growth phase
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-E. coli = 17 min
-Staph. aureus = 27 min - Myco. leprae = 20 days |
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Describe the maximum stationary phase
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-Cell divisions = cell deaths
-Growth rate slows down due to accumulation of wastes, depletion of nutrients, and over crowding |
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Describe the logarithmic death phase
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-Death rate > reproductive rate
-Few cells still survive, curve never reaches zero |
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Define sterilization
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Process of destroying all forms of life, including spores and viruses using either physical or chemical agents
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Define disinfection
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Process by which all vegetative cells are killed, but not spores unless prolonged contact
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Define disinfectant
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Chemical substance, which is toxic to skin and mucous membranes, kills veg. cells and viruses, but not spores unless prolonged contact
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Define antiseptic
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Chemical substance, which is not toxic to skin or mucous membranes, kills vegetative cells but not spores
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Define bactericidal
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-Inhibits growth and kills vegetative cells (ie. autoclave, extreme pH)
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Define bacteriostatic
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-Inhibits growth, but does not kill vegetative cells (ie. refrigerator)
-Temporary suspension of bacterial activities |
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List the different ways of pressure and heat sterilization
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Autoclave, boiling of material, tyndallization, and dry heat
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What does the mechanism of sterilization by heat involve?
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Denaturation of cell proteins and melting of the membrane lipids
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Describe the autoclave of material method of pressure and heat sterilization
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-Pressure cooker (steam under pressure)
-121C temp. -15lb psi -15-20 min |
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Describe the boiling of material method of pressure and heat sterilization
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-20 min
-considered emergency sterilization -kills pathogens + other bacteria -no effect on spores |
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Describe tyndallization method of pressure and heat sterilization
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-Exposure to moist steam (100C) at atm. pressure for 1 hour on 3 consecutive days
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What is the advantages and disadvantages of tyndallization
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-Adv: heat sensitive materials can be processed (which the autoclave cant)
-Dis: Time consuming |
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Describe using dry heat method of pressure and heat sterilization
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-Dry heat of 160C-180C
-1.5-3 hours -No pressure -No moist heat |
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What are some chemical solutions used for sterilization
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Phenol, Chlorhexidine, Halogens, Alcohols, heavy metals, Surfactants, and oxidizing agents
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Who was the first to use phenol? For what? What theory was applied?
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-Lister used phenol as an aerosol disinfectant for surgical instruments
-Applied germ theory to surgery |
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What is the mechanism of action of using phenol?
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-Disruption of cell membrane (dissolve/melt lipids)
-Denaturation of protein gates -Denaturation of enzymes |
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What is chlorhexidine used for?
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-Disinfection of skin and mucous membranes
-Combined with a detergent or alcohol -Also used for surgical hand scrubes + preoperative skin preparation of patients |
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What is the mechanism of action of using chlorhexidine
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-Disruption and damages cell membrane (melts lipids + denatures proteins)
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Why are halogens used as chemical solutions for sterilization?
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-Strong oxidizing agents (removes H-atoms or bonds)
-Iodine/chlorine |
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What is the mechanism of action of using halogens
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Inhibits proteins and denatures proteins
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What is the mechanism of action of using alcohols
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-Denatures protein, enzymes
-Dissolves (melts) lipids |
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What are some heavy metals used as chemical solutions for sterilization
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Silver, copper, Mercury, Silver Nitrate, and Copper sulfate
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What is the mechanism of action of using heavy metals towards amino acids
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-Combines with SH-groups on amino acids = noncompetitive inhibition of enzymes + denaturation of proteins
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What is the mechanism of action of using heavy metals in high and low concentration?
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-Low conc. = bacteriostatic effect
-High conc. = bactericidal effect |
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Describe the oligodynamic effect
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Inhibition of microbial growth due to contact with heavy metal ions
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How does surfactants work?
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lower the surface tension of water (prevents attraction of water molecules) and often used with other disinfectants to increase effectiveness
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What is the mechanism of action of using soaps and anionic detergents?
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-Removal of dead skin and debris
-Coats cell wall + may injure + cause cell lysis -Interferes with active transport -Mechanical removal of microbes through scrubbing |
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What is the mechanism of action of using Quaternary ammonium compound "quats"
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-Used in industries, restuarant, + labs
-Denaturation of enzymes + proteins -Melts lipids in cell membrane |
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What type of chemical solution is Hydrogen peroxide? How does it work?
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-Oxidizing agent
-Good antiseptic for irrigation of open wounds because of its cleansing action and the release of oxygen due to presence of catalase |
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What is the mechanism of action of using oxidizing agents
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Oxidizing cellular components
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What is a chemical gas that is used for sterilization? What is the mechanism of of action?
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-Ethylene oxide
-Denaturation of proteins in cell wall, cell membrane, and enzymes |
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What is the characteristics of Ethylene oxide?
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-Kills all microbes + spores
-Req. long exposure (4-24 hours) -Toxic -Explosive in pure form, mixed with nonflammable gas such as freon, CO2, or N2 gas to prevent explosions -High penetrative ability |
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How is ethylene oxide used?
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Sterilization of medical supplies, plastic ware, mattresses, textiles, artificial heart valves
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When are microbiological filters used?
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sterilization of heat sensitive materials like carbohydrates, vitamins, and antibiotics
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What are the 2 types of microbiological membrane filters
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-Millipore filter- (nitrocellulose)
-HEPA Filter (High effeciency particulate air filtration)- (Cellulose acetate) |
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Describe the millipore filter, also include pore size
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-Most commonly used
-Most effective -Electrostatic forces do play some role in filtration -Pore size: 0.45, 0.22, 0.01 microns |
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Describe the HEPA filter
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Commonly used:
-in laminar flow hoods (negative pressure hoods) -in filtering exhause systems I biohazard buildings |
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Describe the effect of UV light in sterilization
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-260nm lethal
-Thymine-Thymine dimers -Incorrect DNA replication and RNA synthesis, and inhibits protein synthesis |
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What are the disadvantages of using UV light
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-Poor penetration power (glass/plastic petri dishes, fluids, solid media)
-Little effect on spores |
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Describe photoreactivation
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-90% effective
-Photoreactivation enzymes -Recognizes T-T dimers -Breaks T-T dimers -Restore normal DNA structure |
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Describe excision
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-10% effective
-Independent of white light -DNA polymerases and ligases -Recognize T-T dimer -Excision + removal of T-T dimers -Repair damaged DNA by synthesis of new DNA to fill in gap |
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Describe ionizing radiation
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-Gamma + X-Rays
-ionization of water molecules (splits water into free radicals; supercharged ions) -Denatures proteins + DNA |
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Why are gamma rays effective? Where is it used?
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-Greatest penetration power
-Used in food preservation of spices |
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What are the different types of physical parameters?
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-UV light (non-ionizing radiation)
-Gamma + X-Rays (ionizing radiation) -Ultrasonic waves |
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What is the purpose of pasteurization
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-Kills pathogens
-Reduce total number of normal flora (ie. in milk: Strept. lactis and Lactobacillus acidophilus) -Milk is not sterile following pasteurization |
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What is pasteurization
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-Controlled heating below boiling (ie. milk, beer, wine)
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What are the 2 methods of pasteurization? Describe them
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-High Temp. Holding Time (HTHT): 72C for 15s
-Low Temp. Holding Time (LTHT): 63C for 30min (ie. small dairy farmers) |
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What is another type of use of pasteurization?
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Hospital anesthesia masks are pasteurized at 80C for 15 min.
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Describe the Ultra High Temp. (flash) method
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-Sterilization of milk
-Process: under vacuum, less than 5s, (74C > 140C (3s under vacuum) > 74C) -Used for coffee creamers, areas of poor refrigeration |
