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- Destruction or removal of all forms of microbial life, including endospores but with the possible exception of prions
- -usually done by steam under pressure or a sterilizing gas, such as ethylene oxide
Define Commercial Sterilization
- sufficient heat treatment to kill endospores of Clostridium botulinum in canned food
- -more-resistant endospores of thermophilic bacteria may survive but they will not germinate and grow under normal storage conditions
- Destruction of vegetative (growing) pathogens
- -may make use of physical or chemical methods
- Destruction of vegetative pathogens on living tissue
- -treatment is almost always by chemical antimicrobials
- removal of microbes from a limited area, such as the skin around an injection site
- -mostly a mechanical removal by an alcohol-soaked swab
- treatment is intended to lower microbial counts on eating and drinking utensils to safe public health levels
- -may be done with high-temperatue washing or by dipping into a chemical disinfectant
What does it mean when something is "cidal" or "static"?
cidal- kills whatever it is made for ex. mesocidal
static-halts growth (like a fridge is microbial static for mesophiles)
What is DRT? What are the two factors that can affect DRT?
- DRT is the time it takes to kill 90% of the microbial population
- -varies between MOs
- *the Harsher the procedure, the shorter the DRT
- *the easier the MO to kill, the shorter the DRT
- *does not vary under a defined set of conditions (constantly killing 90%)
How can the number of microbes and degree of microbial resistance influence the effectiveness of microbial treatments?
More microbes= more time to kill them all
The easier they are to kill, the less time it takes to kill them
How can environmental influences and exposure time influence the effectiveness of microbial treatments?
Cold, dirty objects are harder to treat-disinfection is a chemical process, which occurs faster at warmer temperatures-dirt:organic matter; can absorb disinfectant and prevent the killing of MO*the longer you kill, the more you kill
What are the three factors of cell anatomy that are important in how microbial control agents effect the cells?
- These 3 are targets for killing
- membrane-regulates what enters the cell. If damaged, cell with lyse
-do certain jobs that keep the cell alive. If damaged, cell will die
-controls the synthesis of proteins. If damaged cell will die
What is the purpose of boiling? What are it's uses and limitations?
Common uses: for cleaning drinking water, boil for 2 minutes
*boiling is 100C
It denatures the proteins of the MO (like a hardboiled egg)
- Limitations: some spores survive boiling
- *form of disinfecting or sanitization
What is the purpose of an autoclave? How does it work? What are it's uses and limitations?
- Works like a pressure cooker
- -the steam is much hotter than boiling
- -121C for 15 minutes
- Microbes cannot survive
- -reliable sterilization
only for objects that can get hot and wet
What is the purpose of pasteurization? How does it work? What are it's uses and limitations?
Pasteur's Idea-goal is to kill pathogens and lower total MO count without significantly altering taste or nutrient content
milk, beer, fruit juice, canned crab meat, marschino cherries
- timing: 63C/30min;72C/15sec;
- UHT 74C-->140C-->70C in 5 seconds
: ultra high temperature
-it extends the products shelf life and makes the product safe to consume
What is the purpose of oven sterilization? How does it work? What are it's uses and limitations?
- Uses Dry Heat
- -170C for 2 hrs
Organic Molecules + Heat--> CO2
Air conducts heat much more porrly than water, that's why it takes longer than autoclaving
use for objects that can get hot but not wet (like glassware)
flaming loops, incineration of infectious waste
What is the purpose of filtration? How does it work? What are it's uses and limitations?
This is used for fluids that are heat-liable, or damaged by heat such as culture media enzymes, vaccines, and antibiotic solutions
- Uses: can be used for water at (.2μm)
- HEPA filters (.3μm) for burn wards, clean rooms, operating filters
What is the purpose of refrigeration? How does it work? What are it's uses and limitations?
normally set at 4C, it is microbiostatic for mesophles
permits slow growth of psychrotrophs (usually non pathogens except for Lysteria)
What is the purpose of high osmotic pressure? How does it work? What are it's uses and limitations?
The more hypertonic the solution is, the higher the osmostic pressure is
examples: salting, sugaring, drying of foods
many molds are osmotolerant, explaining mold growth on bread, etc
What is the purpose of Ionization radiation? How does it work? What are it's uses and limitations?
A Sterilization process
gamma rays, X-rays, electron beams (all are highly penetrating)
- mechanism: production of hydroxyl radicals in water and direct damage to DNA
- H2O + IR --> OH-
- * these hydroxyl radicals are potent oxidizers of DNA and proteins
food, (sterilizer of pasteurizer depending on intensity and exposure time), mail, prepackaged disposable medical/dental/laboratory tools
*sometimes referred to as "cold pasteurization" or "electronic pasteurization"
What is the purpose of Non-ionizing Radiation? How does it work? What are it's uses and limitations?
- UV radiation, provided by UV (germicidal) lamps
- -like Tru-D in hospitals to kill c. diff
DNA strongly absorbs UV radiation and is often damaged in doing so
UV rays are poorly penetrating so use is limited mostly to disinfection of surfaces or air
disinfection of well water, operating thearres, barber shops, nail salons
What are the factors related to the effective disinfection?
READ THE LABEL!!
- -type of organism the disinfectant is effective against
- -concentration of the disinfectant
- -whether the disinfectant can contact the microbes (non porous surfaces)
- -contact time
common in household antibacterial soaps; inhibits fatty acids (and thus membrane) synthesis
very effective; binds to and inactivates many microbial proteins; used as a skin antiseptic (e.g. betadine) and to disinfect drinking water (hikers use tablets)
strong oxidizing agent; active ingredient in bleach; used to disinfect drinking water, swimming pools; 10% sol'n can be used in sharps containers or to disinfect surfaces
denatures proteins and dissolves lipid membranes; used as a degermer (injections, hand gel-sanitizers)
just a degermer (provided no anti-bacterial agents have been added to it); but don't underestimate the effectiveness of correct hand washing procedures with soap and hot water
Quaternary Ammonium Compounds
lots of different specific types (e.g. alkyl dimethyl benzyl ammonium chloride, benzalkonium chloride, etc.) Probably disrupts membrane; soapy, very common in household disinfectant products (kitchen and bathroom cleaners, disinfectant wipes, contact lens cleaners, etc)
Pseudomonas can use this as a nutrient!!
A mold inhibitor, often found in soft drinks, cheeses and baked goods (like snack cakes)
same as potassium sorbate
highly effective; one of the few chemicals considered to be a sterilent (when properly used); bind to and denature cell proteins; the active agent in our laboratory bench top cleaning solutions (wavicide)
an explosive and possibly carcinogenic gas-but highly penetrating and effective. denatures proteins; used in autoclave-like devices (gas sterilizers to sterilize hospital equipment (e.g. bronchoscopes) and sealed, disposable materials (swabs, bandages, etc.)
Oxidizing Agent; not very effective on wounds due to catalase in human tissue; but works very well on inanimate surfaces; used to disinfect contact lenses and sterilize food packages like juice boxes
an oxidizing agent found in over-the-counter acne medications-effective against the anaerobic bacteria that dwell deep in the hair follicle
What is the deceasing order or microbial resistance to chemicals?