Chap 7 - Control of Microorganisms: Phys and Chem Flashcards
The destruction of all living microbes, spores and viruses.
Sterilization
When do sterile objects become contaminated?
When exposed to air and surroundings.
Does sanitization sterilize?
No. Sanitation reduces the number of pathogens or discourages their growth
Sanitization does what?
Reduces the numbers of pathogens. Lower level of control
What happens when microbes are at temperatures above their growth ranges?
Proteins and nucleic acids are destroyed, water is removed.
What is one of the most common physical control methods?
Heat
What method of heat uses direct flames to kill microbes?
Incineration
The minimum temperature to kill a species is considered what?
Thermal death point.
Thermal death time is what?
The length of time required to kill a microbial population at a given temperature.
Does hot air sterilization take a short time and does it penetrate?
No - it takes a long time and doesn’t penetrate
Dry and Moist Heat are applied similarly. (T/F)
False. Dry heat requires more time.
Name one tool used for incineration
Bunsen burner
Dry heat quickly burns the microbes. (T/F)
False - it slowly burns
Dry heat creates a moist environment. (T/F)
False - it creates an arid environment.
Dry heat creates an arid internal environment that changes microbial proteins by what?
Oxidation
Moist heat can be used to sterilize.
True
Boiling water kills all spores and inactivates all viruses.
False.
Which penetrates microbes better: dry heat or hot water?
hot water
Moist heat kills microbes by doing what?
Denaturing their proteins.
Autoclaves use what to kill microbes?
Steam, specifically Pressurized steam.
In Autoclaves, _______ increases as _______ increases.
Temperature, Pressure
This machine decreases the cycle time and exposure of sensitive materials to steam (creates saturated steam)
The prevaccum autoclave
If materials are not suited to the autoclave, what form of sterilization is used?
Fractional sterilization / intermittent sterilization (pg. 203)
Pasteurization is a form of _____ heat.
moist
What does pasteurization do?
Reduce bacterial populations in food and drink.
Why is pasteurization used in food & drink?
It reduces spoilage and disease. Kills pathogens and food spoilage organisms
Are bacterial spores affected by pasteurization?
No
What is the only method of pasteurization used to sterilize liquid?
Flash pasteurization.
In regard to filtration, how are microbes filtered? Viruses?
Pores, 0.2 micrometers which are smaller than most microbes. The average filter would allow viruses to pass through.
Can viruses pass through pores?
Yes - they might be able to if they are smaller than 2 micrometers
What does HEPA stand for?
High-efficiency particle air (filter)
What kind of filter are used in hospitals?
HEPA Filters
Can UV Light be used as a Microbial Control path?
Yes.
DNA of the cell absorbs the the UV light, causes adjacent thymine molecules to link together, kinking double helix
UV light does what to microbial growth?
Remember: Disrupts DNA replications and transcription
Disruption in turn reduces population, limits airborne/surface contamination
What are the types of radiation that can sterilize materials?
X Rays | Gamma Rays | Ionizing radiation
This type of radiation forces electrons out of microbial molecules and is used in food products (pasteurizing dose)
Ionizing radiation
Radiation for food is not used for shelf stability. (T/F)
False, it is used. Food is not sterile but removes chances of food born illnesses
Bacteriostatic means what?
Slow multiplication of organisms. Anything with “-static” will reduce the numbers or inhibit growth. Others are: microbiostatic, fungistatic
This form of preservation removes water necessary for microbes to live. (“where there is water, there is no life”)
Drying (used in meats, fish, cereals) ie beef jerky. Do not confuse with SALTING which is the DIFFUSION of water out of the cell.
This form of preservation creates hypertonic environment (when water is diffused out of the cell) causes water loss from microbes then it will die.
Salting
Does low temperatures (ie kept in refrigerator) also preserve food?
Yes - lower microbial metabolic and growth rates, retarding spoilage
When did medicinal chemicals come into widespread use? By who?
In the 1800s & Lister
What is the definition of “disinfectant”?
chemical used to kill or inhibit pathogenic microorganism on a lifeless object such as a tabletop.
Disinfectants are used on ____, while antiseptics are used on ____.
Surfaces/Objects | Skin
Microbicidals do what?
Inactive enzymes of organisms; interferes with metabolism. Kill!!!
De-germing means what?
removing organisms from an object’s surface.
Hand-soap has a pH of what?
12
To be a useful as a disinfectant or antiseptic it should:
• Kill or slow growth of microbes and be non-toxic to animals or humans • Be soluble in water or alcohol, and easy to apply • Have a relatively long shelf life • Be used in a diluted form • Act in a short time • Be non-staining and non-corrosive (doesn’t burn skin) • Be odorless, easy to obtain • Be relatively inexpensive
What are things to consider with chemical agents at disinfectants or antiseptics?
- Microbial susceptibility - leave the solution to kill on long enough.
- Temperature and pH – consider temp of are
cleaning, temp/ph can change reaction to disinfectant. - Concentration- higher conc more effective.
- Environment – bioburden, more organisms present longer it takes to clean.
- Endospore formers
Thermal death time is what?
The time needed to kill the species.
What is the thermal death point of E. Coli
55 mins to 2 hours (320F / 160C)
When using a chemical should you concern yourself with how long to leave the solution on the surface?
Yes. Microbial susceptibility is different for each organism. You must take this into consideration.
Does the temperature of a room effect the growth or organisms?
Yes.
Can you kill endospores by boiling them?
The only sure way to rid of spores is to use an autoclave or incineration.
What is the phenol coefficient?
Indicates disinfecting ability. Everything is compared to phenol which is given a 1.
Is a phenol coefficient of 2 or 200 better? How about .04? Which one is most effective?
.04 is worse than phenol. 200 is better than 2.
What do we look for when using the disk diffusion method for testing effectiveness of a chemical?
zone of inhibition
True or False: Chlorine is used in municipal water supplies?
True!
True or False? Iodine is used to clean wounds.
True
What is the purpose of iodopors?
release idodine over a long period of time.
Chemical agents that contain _________ __________, cross link proteins together so they can no longer function.
Heavy Metals
Chemicals containing __________ denature proteins and disrupt the membrane (dissolve lipids)
Alcohol
Which is more effective: 70% alcohol hand sanitizer or 90%? Why?
70% because it evaporates slower than 90%
mechanically remove organisms from a surface
degerm
_________ emulsify and solubilize particles clinging to a surface.. An example is soap.
Surfactants
A strong surfactant that alters the membrane and cause cell lysis
detergent
How does soap removes organisms from your hands?
Soap has a positive charge. Bacteria has a negative charge. Soap surrounds bacteria!
