Control of Microbial Growth Flashcards
What is the definition of Sterilization?
Removal of all microorganisms
~ Sterile item is absolutely free of microbes, endospores and viruses
What is the definition of Disinfection?
Eliminates most pathogens
~ Some viable microbes may exist
What is the definition of Pasteurization?
Brief heat treatment used to reduce organisms that cause food spoilage
What is the definition of Preservation?
Delaying spoilage of food by adding growth inhibition ingredients or adjusting storage conditions to impede growth
How can Sterilization be achieved?
filtration, heat, chemicals, and irradiation
How can Disinfection be achieved?
filtration, heat, chemicals, and irradiation
What are Disinfectants used to disinfect?
inanimate objects and surfaces
What are Antiseptics used to disinfect?
living tissues
What are the 4 physical methods of controlling microbial growth?
- Heat
- Irradiation
- Filtration
- Mechanical removal – “scrubbing”
What is the chemical method of controlling microbial growth?
By use of a variety of antimicrobial chemicals
Describe 3 methods of using moist heat for antimicrobial control.
- Boiling (100° C)
~ Destroys most microorganisms and viruses
~ does not destroy endospores
2. Pasteurization ~ Pasteur developed to avoid spoilage of wine ~ significantly reduces organisms ~ increases shelf life of food ~ Most protocols employ HTST method (Heated to 72°C and held for 15 seconds)
- Pressurized steam - Autoclave
~ Achieves sterilization at 121°C and 15psi in 15 minutes
(Effective against endospores)
Which is more effective for sterilization: moist or dry heat?
Moist heat
How does the Incineration method of dry heat sterilize?
It oxidizes the cells to ashes
What method of microbial growth control is used to destroy medical waste?
The Incineration method of dry heat sterilization
Hwo does liquid filtration work?
Membrane filters allow liquids to flow through but traps microbes on filter
What is liquid filtration used for?
Heat sensitive fluids
Give an example of air filtration.
High efficiency particulate air (HEPA) filter removes microbes from air
~ Filter has 0.3µm pores to trap organisms
Describe Electromagnetic radiation.
~ Shorter wavelength, higher frequency = more energy
~ Can be ionizing or non-ionizing
Describe Ionizing radiation.
Radiation able to strip electrons from atoms
~ Causes damage to DNA and to plasma membrane
What is Ionizing radiation used for?
Used to sterilize heat sensitive materials
ex. Medical equipment, surgical supplies, medications
What is ionizing radiation most and least effective against?
Gram Negatives = most susceptible
Endospores = most resistant
Describe Non-ionizing radiation (ultraviolet radiation).
Damages DNA by causing thymine dimers
What is non-ionizing radiation most and least effective against?
Growing microorganism = most susceptible
Endospores = most resistant
What is Non-ionizing radiation used for?
to destroy microbes in air, drinking water and surfaces
What can limit non-ionizing radiation?
Thin films or coverings can limit effect (i.e., poor penetrating power)
What are alcohols’ mode of action?
- Coagulation of proteins ands essential enzymes
2. Damage to lipid membranes
What is the limitation of alcohol?
Evaporates quickly, limiting contact time
What is alcohol not effective against?
endospores and some viruses
What do aqueous solutions of 60% - 80% isopropyl or ethyl alcohol kill?
bacteria and fungi
What is Halogen’s mode of action?
Oxidizing proteins and other cell components
What does Chlorine destroy?
All microorganisms
What are 2 examples of Halogens?
chlorine and iodine
What does iodine destroy?
vegetative cells
What is the active ingredient in Lysol and Amphyl?
Phenolics (carbolic acid)
What is a Phenolic’s mode of action?
- Destroy plasma membrane
2. Denature proteins
What can kill Mycobacterium at high concentrations?
Phenolics
What are Quaternary Ammonium Compounds’ mode of action?
- Reduces surface tension
~ Aids in removal of dirt and organic matter
~ Facilitates mechanical removal of organisms - Positive charge attracts Quats to negative charge of cell surface
~ Reacts with membrane
What are Quats strong and weak against?
- Destroys vegetative bacteria and some viruses
2. Not effective on endospores, mycobacteria, and some viruses
