Flashcards in Ch 07 Microbial Growth Deck (56):
What does labile mean?
In what situation if filtration the only way to eliminate microbes?
When dealing with heat labile microbes.
What does sepsis mean?
What does asepis mean?
Free of contamination.
What does sterilization mean?
Removing all microbes.
What does disinfection mean?
Removing pathogens off objects.
What does antisepsis mean?
Removing pathogens from living tissue.
What does degerming mean?
Removing microbes from a limited area. Hanswashing.
What does sanitation mean?
Lowering microbe counts on eating utensils.
What is meant by biocide/germicide?
What is meant by bacteriostasis?
Inhibiting, not killing, microbes.
The usual definition of sterilization is the removal or destruction of all forms of microbial life; how could there be practical exceptions to this simple definition?
Sterilization implies to the absence of prions, tough to do.
Describe the rate of microbial death caused by treatments with microbial control agents.
Microorganisms die at a constant rate.
Name four params microbial treatments depends upon.
Number of microbes
Time of exposure
Which microbes are chemically resistant?
Which are physically resistant?
Chem: Gram-neg, capsules
How is it possible that a solution containing a million bacteria would take longer to sterilize than one containing a half-million bacteria?
Rate of microbial death: The number of microbes. The more microbes to begin with, the longer it takes to eliminate the entire population.
other factors: environment influences; time of exposure; microbial characteristics.
Describe the effects of microbial control agents on cellular structures.
- Attacking the cell wall
- Alteration of membrane permeability
- Damage to proteins
- Damage to nucleic acids
Would a chemical microbial control agent that affects plasma membranes affect humans?
Yes because all cells including human cells have plasma membrane. Anything that attacks the plasma membrane will attack you.
It is important to develop a microbial agent that targets components of the microorganism that are not present in the host cell.
What are three methods to kill microbes?
Cell membrane damage
Nucleic acid damage
Describe Thermal Death Point (TDP), Thermal Death Time (TDT) and Decimal Reduction Time, (DRT)?
Thermal Death Point: lowest temp which all cells are killed in 10 minutes.
Thermal Death Time: time which all cells are killed.
Decimal Reduction Time: minutes to kill 90% of population.
How does an autoclave work?
Heat: 121 C.
Pressure: 15 PSI
What is Pasteurization?
Reduces spoilage, does not sterilize.
How does dry heat kill?
What are physical methods of microbial control?
Differentiate ionization from nonionization radiation.
Ion: short WL, X-rays 200 nm
Non: UV, 260 nm
What are the principles of effective disinfection ?
Principles of effective disinfection:
1. Concentration of disinfection
2. Nature of the material- organic materials present that might interfere with the action of the disinfectant
4. Time- disinfection is a gradual process
Interpret the results of use-dilution test and disk-diffusion method
Use-dilution: metal/glass cylinders dipped into cultures of test bacteria and then dried. placed into a soution of the disinfectant for ten minutes then transfered to a medium that permits growth of any surviving bacteria. the effectiveness of the disinfectatnt is determined by the number of cultures that can grow (more cultures that grow, less effective it is)
Disk-diffusion: paper disks soaked in chemical and placed on agar plate that has previously been incubated and innoculated with the test organism. after incubation, if test is effective, a clear zone represendting inhibition of growth can be seen around the plate.
Interpret the results of use-dilution test.
Cylinders dipped into cultures of test bacteria and then dried. placed into a solution of the disinfectant for ten minutes then transferred to a medium that permits growth of any surviving bacteria. the effectiveness of the disinfectant is determined by the number of cultures that can grow.
Interpret the results of disk-diffusion method.
Paper disks soaked in chemical and placed on agar plate that has previously been incubated and inoculated with the test organism. after incubation, if test is effective, a clear zone representing inhibition of growth can be seen around the plate.
If you wanted to disinfect a surface contaminated by vomit and a surface contaminated by a sneeze, why would your choice of disinfectant make a difference?
No single chemical is good for all applications. It would depend on what the situation dictates. Use of biguanides would be useful on the sneeze because of chlorhexidine.
What is a biguanide?
Disrupt plasma membrane.
Which is more likely to be used in a medical clinic laboratory, a use-dilution test or a disk-diffusion test?
Disk-diffusion test. Because this is what is used to measure the effectiveness of specific antibiotics on certain microbes.
-A use-dilution test would be more appropriate in industrial uses because it measures what is the lowest amount of chemical needed in a solution to effectively kill microbes.
What do phenol/bispheonols do and give some examples?
Disrupt plasma membrane in phospholipid bilayer.
What do halogens do and give some examples?
Iodine: Tinctures of iodine in aqueous ETOH. Iodophors in organic molecules. Alter protein synthesis and membranes.
Chlorine: Bleach, oxidizing agents.
What do alcohols do and give some examples?
Why is 100% ETOH not as effective as 65%?
Protein denaturation and dissolving the lipid membrane. ETOH
Requires some water to be effective as denaturation.
What do heavy metals do and give some examples?
Silver nitrate eye drops for childen
Oligodynamic action, denature proteins
What type of germs to quarternary ammonium compunds (quats) work on?
Chemical food preservatives
Organic acids inhibit metabolism
Nitrites prevent endospore germiantion
Antibiotics prevent cheese spoilage
What do aldehydes do and give an example?
What is an example of a gaseous sterilant?
Ethylene oxide gas
What are two examples of a peroxygens and what do they do?
H2O2 hydrogen peroxide
Is Betadine an antiseptic or a disinfectant when it is used on skin?
An antiseptic applied on skin.
Disinfectant applied on objects.
What characteristics make surface-active agents attractive to the dairy industry?
Acid-Anionic Sanitizers: important in cleaning dairy utensils and equipment; Non-toxic; non-corrosive; and fast acting.
What chemical disinfectants can be considered sporicides?
What chemicals are used to sterilize?
Ethylene oxide gas
Explain how the type of microbe affects the control of microbial growth.
gram negative bacteria are more resistant than gram positive bacteria to disinfectants and antiseptics.
List the order of most resistant microbes.
Viruses wo envelopes
Viruses w envelopes
Which class of cleaners disrupts plasma membrane?
Which class of cleaners causes protein denaturation?
Which class of cleaners are oxidizing agents?
Which class of cleaners causes enzyme inhibition?
Which physical method used to control microbe growth causes protein denaturation?
Which physical method used to control microbe growth causes decreased chemical reactions?
What does a glutaraldehyde work on?
What is oligodynamic action?
Metals acting as antimicrobial agents