Chapter 8 Flashcards
(46 cards)
What is the definition of “sterilization”?
The process by which all living cells, spores, and acellular entities (viruses, viroids, prions, satellites) are either destroyed or removed from an object or habitat.
A sterile object = totally free of viable microorgs, spores, other infectious agents.
Given some examples of things that may be sterilized by FILTRATION.
- Air
- Heat-sensitive solutions (ex. pharmaceuticals)
- Ophthalmic solutions
- Antibiotics
Given some examples of things that may be sterilized by UV LIGHT.
UV light typically disinfects as it does not kill spores.
- Air
- Exposed surfaces (ex. culture surfaces)
- Water (ex. thin water films)
- Cellphones
Give some examples of things that may be sterilized by IONIZING RADIATION.
May achieve disinfection or sterilization depending on intensity and time of exposure.
- Heat-sensitive materials (ex. medical devices, sutures)
- Disposable plastics (ex. syringes)
- Food (poultry, pork, chicken, beef, fruit, veggies, spices)
Given some examples of things that may be sterilized by ETHYLENE OXIDE.
- Solid heat-sensitive materials (plastic Petri dishes, syringes and sutures)
- Usually not liquids, which are difficult with residual EtO (toxic)
Describe how biological safety cabinets work.
Biological safety cabinets filter air through HEPA filters. Contaminated air enters the cabinet and circulates through various parts of the system before exiting.
HEPA (High Efficiency Particulate Air) filters are used in laminar flow biological safety cabinets and are made of fiberglass. They filter out >99.7% of 0.3 micron particles.
True or False: the autoclave is not an effective sterilization method for glass pipettes because they are delicate and the heat can cause the material to melt.
FALSE: Autoclave is readily available for glass instruments since glass is not heat-sensitive. Glass pipettes may be placed in a container or wrapped for sterilization.
True or False: Tryptic soy broth tubes may be cleaned with an autoclave, even though an autoclave uses steam to clean the instruments.
TRUE: The liquid (broth) is NOT heat sensitive, and the autoclave sterilizes liquid in test tubes in one method.
Disinfectant(s)/antiseptic(s) that can treat a LAB BENCH?
70% alcohol, bleach (10% javex), 0.5-3% phenolics
Disinfectant(s)/antiseptic(s) that can treat SKIN BEFORE SURGERY?
Iodine (may burn skin though, so iodophor can also be used)
Disinfectant(s)/antiseptic(s) that can treat SMALL MEDICAL INSTRUMENTS?
70% ethanol, 0.2% quaternary ammonium compounds (ex. benzalkonium)
Provide an example of an antibiotic that inhibits CELL WALL SYNTHESIS. Briefly explain the mode of action.
Penicillin (bactericidal): inhibits peptidog. synth. in growing cells, activates bacterial holin proteins which form holes in plasma membrane causing leakage and death
Provide an example of an antibiotic that inhibits PROTEIN SYNTHESIS. Briefly explain the mode of action.
Streptomycin (bactericidal): binds to 30S ribosome producing mistranslated proteins which may be inserted in plasma membrane stimulating a stress response. Hydroxyl radicals released = cause cell death
Explain the method of action of CHLORAMPHENICOL
Chloramphenicol is an antibiotic that inhibits peptidyl transferase on 23S rRNA preventing peptide elongation, so it is bacteriostatic.
True or False: Bactericidal antimicrobial agents kill pathogens, nonpathogens and endospores.
FALSE: Not all bactericidal agents are effective at killing endospores.
True or False: Disinfectants are usually chemical agents used on inanimate objects that kill most vegetative cells, but not spores.
TRUE
True or False: Disinfectants and sanitizing agents are similar in that they both may reduce microbial populations to safe levels based on public health guidelines.
TRUE
Define antiseptic agents.
Antiseptics are chemical agents that kill or inhibit growth on the surface of tissue to prevent infection without destroying that tissue. They are less toxic than disinfectants.
What are the four microbial control methods?
CAMP (“Can’t All Men Piss?”)
Chemical control agents: disinfectants, antiseptics
Antimicrobial agents (Penicillin, aminoglycoside, chloramphenicol, etc)
Mechanical removal: filtration
Physical control: heat (moist or dry), radiation
True or False: Dry heat and moist heat are not applied differently because they both achieve the same results.
FALSE: dry heat requires long periods of exposure at high temperatures (changes proteins, removes water, slowly burns). Moist heat (ex. boiling water) is faster and effective at a lower temperature (denatures proteins).
How long does the bacteria Cloststridium botulinum last until it is killed in moist heat? In dry heat?
Moist: lasts 5min at 121 Cº
Dry: lasts 2h at 160 Cº
What is the killing capacity of moist heat?
Destroys viruses, fungi and bacteria. Does not destroy endospores nor sterilizes. Degrades nucleic acids, denatures proteins, and disrupts membranes.
Describe how an autoclave (steam sterilization) works.
- Air is replaced with steam at 121 ºC and 15 psig (pounds per square gauge)
- Effective against all microorganisms (including endospores, 20min exposure)
- Quality control includes strips with Geobacillus stearothermorphilus
How does pasteurization work?
- Typically done on milk, beer, other beverages
- Temperatures well below 100 ºC slows spoulage and reduces total load of organisms
