chapter 11 bio 115

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  1. controlling microorganisms
    • physical, chemical, and mechanical methods to destroy or reduce undesirable microbes in a given area
    • primary targets are microorganisms capable of causing infecting or spoilage:
    • vegetative bacterial cell and endospores (hardest microbial to get rid of)(reproductive)(mold)
    • fungal hyphae (makes up body)(mold) and spores, yeast
    • protozoan trophozoites (ex Malaria) and cysts
    • worms
    • viruses
    • prions ( hardest to get rid of)
  2. what are the two primary targets that are hardest to destroy
    endospores and prions
  3. trophozoiles
    mature motile form
  4. cyst
    dormant, non-motile, don't move around on their own
  5. relative resistance of microbes
    • highest resistance- bacterial endospores, prions
    • moderate resistance- Pseudomonas species, Mycobacterium tuberculosis (used in lab), Staphylococcus aureus (used in lab), protozoan cysts
    • least resistance- most bacterial vegetative cells, fungal spores and hyphae, yeast, enveloped viruses, protozoan trophozoites
  6. sterilization
    • a process that destroys all viable microbes, including viruses and endospores; microbicidal
    • getting rid of all microbes including endospores
  7. disinfection
    • a process to destroy vegetative pathogens (NOT endospores) on inanimate objects
    • on non living objects
    • don't kill endospores
  8. antiseptic
    • chemical agents applied directly to exposed body surfaces (living tissue)
    • iodine, alcohol peroxide before operation on living tissue
  9. sanitization
    • any cleaning technique that removes microbes to reduce the microbial load; reduce the potential for infection/spoilage 
    • soap of some kind of chemical to drop the  number of microbes to a safer level
    • fork and spoon in restaurant
  10. degermation
    • process of mechanically reducing the microbial load on living tissue; often involves scrubbing the skin and/or immersing it in chemicals
    • chemical and scrubbing reduces over all load of living tissue
    • pre operative scrub before operation
  11. how can we tell if a microbe is dead
    • microbial death-permanent loss of reproductive capability, even under optimum growth conditions
    • can't reproduce
  12. factors that affect death rate
    • the effectiveness of a particular agent is governed by several factors:
    • number of microbes-an object that we are trying to treat, the larger the population the harder it is going to treat
    • nature of microbes in the population-are they vegetative state or are they endospores which will be harder to treat
    • temperature and pH of environment
    • concentration or dosage of agent-the stronger the chemical or the more you put on the higher the death rate
    • mode of action of the agent-does it target cell walls
    • presence of solvents, organic matter or inhibitors-determines how fast or slow they die
  13. practical concerns in microbial control
    • selection of method of control depends on circumstances
    • does the application require sterilization or is disinfection adequate?-are endospores present
    • is the item to be reused?-needs to come back in tact ex not going to put paper towel in heat
    • can the item withstand heat, pressure, radiation, or chemicals?
    • will the agent penetrate to the necessary extent?- can it penetrate all the way
    • is the method cost- and labor- efficient, and is it safe?
  14. antimicrobial agents modes of action
    how the agent works against the microbes
    • cellular targets of physical and chemical agents:
    • the cell wall-cell wall becomes fragile and cell lyses-some antimicrobial drugs, detergents, and alcohol
    • the cell membrane- loses integrity- detergents, create leaky gaps
    • cellular synthetic processes (DNA, RNA)-prevention of replication, transcription- some antimicrobial dugs, radiations, formaldehyde, ethylene oxide
    • protein-interfere at ribosomes to prevent translation, disrupt or denature proteins-alcohols, phenols, acids, heat
  15. denature
    • destroy a proteins shape
    • if you screw up shape makes it  unfunctional
  16. moist heat
    • lower temp and shorter exposure time
    • coagulation  and denaturation of proteins
  17. dry heat
    • moderate to high temperatures and longer exposure time
    • dehydration, alters protein structure
    • incineration which mean flaming the loops in lab
  18. thermal death time (TDT)
    • shortest length of time required to kill all test microbes at a specified temperature
    • time is going to be what we are looking for
    • to kill endospores need to get above 100 degree
  19. thermal death point (TDP)
    • lowest temp required to kill all microbes in sample in 10 min
    • temp is what we are looking for
  20. steam under pressure
    • provides sterilization
    • autoclave-15psi/121C (249.8F) 10-40min
    • steam must reach surface of item being sterilized
    • item must not be heat or moisture sensitive
    • mode of action-denaturation of proteins, destruction of membrane and DNA-that's why it is so effective
  21. nonpressurized steam
    • tyndallization -intermittent sterilization for substance that cannot withstand autoclaving
    • items exposed to free flowing steam for 30-60 min, incubated for 23-24 hours and then subjected to steam again
    • repeat cycle for 3 days
    • used for some canned food and lab media which cant withstand pressure
    • disinfect
  22. boiling water
    • boiling at 100C (212F) to 30 min to destroy non-spore-forming pathogens
    • disinfects
  23. pasteurization
    • heat is applied to liquids to kill potential agents of infection and spoilage without destroying the food flavor or value
    • 63C (145.4F)-66C (150.8F) for 30 min (batch method)
    • 71.6C (160.8F) for 15 sec (flash methods)
    • not sterilization-kills non-spore-forming pathogens and lowers overall microbes count; does not kill endospores or many nonpathogenic microbes
    • Pasteur created this prevent spoilage of ex. milk and food
  24. dry heat
    • using higher tem than moist heat
    • incineration-flame or electric heating coil-ignites and reduces microbes and other substances to ashes and gas, limited to metal and heat resistant glass
    • dry ovens-150-180C (302-356F) coagulate proteins
  25. microbiostatic
    • slows the growth of microbes
    • cold
    • used to preserve food, media and cultures
    • refrigeration 0-15C (32-59F) and freezing below 0C
  26. desiccation
    • drying out
    • gradual removal of water from cells, leads to metabolic inhibition
    • not effective microbial control-many cells retain ability to grow when water is reintroduced
    • lyophilization-freeze drying; preservation
  27. ionizing radiation
    • deep penetrating power that has sufficient energy to cause electrons to leave their orbit, breaks DNA
    • gamma rays, x-rays, cathode rays
    • used to sterilize medical supplies and food products
  28. nonionizing radiation
    • very little penetrating power-item to be disinfected must be directly exposed
    • UV light creates thymine dimers which interfere with normal DNA replication and transcription
  29. filtration
    • physical/mechanical removal of microbes by passing a gas or liquid through filter
    • used to sterilize heat sensitive liquids and air in hospital isolation units and industrial cell rooms
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chapter 11 bio 115
2013-10-14 01:28:21
chapter 11 bio 115

chapter 11 bio 115
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