Chapter 9: Control of Microbial Growth- Part 2 Flashcards
Filtration of fluids
Nylon membranes of defined pour sizes
- 0.45 um
- 0.20um
How are the filters sterilized for filtration of fluids?
Irradiation
What does filtration of fluids filter out?
Bacteria but NOT viruses or prions
HEPA
High-efficiency particulate air filters
HEPA uses
- Room ventilation
- Laminar flow hoods
- Powered Air-Purifying Respirator (mask covering face)
Types of radiation
Ionizing
Ultraviolet
Microwaves
Ionizing radiation
Damages things by causing electrons to pop off
UV light
Can be damaging to DNA
Microwaves
Use hear as a way to destroy things
High pressure
Like an autoclave without the heat or steam (up to 130,000 psi)
Potency
How well something gets rid of microorganisms
Levels of potency
Sterilants
High-level disinfectants
Intermediate-level disinfectants
Low-level disinfectants
Sterilants
Kills everything!
High-level disinfectants
Kills viruses and all vegetative bacteria (but not spore formers!)
Intermediate-level disinfectants
Kills all vegetative bacteria and most viruses
Low-level disinfectants
All vegetative bacteria and enveloped (membrane-bound) viruses
Which type of viruses are more/very hardy?
Non-enveloped
Why are sterilants not always used?
They could damage what you are trying to clean, cost, etc.
You have been given a sample of one type of bacteria and one virus and have been asked to kill the bacteria and inactivate the virus using the least potent chemical treatment to do so. The bacteria do not produce endospores and the virus is enveloped. What would you use?
Low-level disinfectant
Things to consider when selecting the appropriate germicidal chemical
Toxicity Activity in the presence of organic matter Residue Cost and availability Storage and stability Environmental risk
Germicidal
Killing bacteria and inactivating viruses
Chemical classes of germicidal chemicals
Alcohols Aldehydes Biguanides Ethylene oxide Halogens Ozone Peroxygens Phenolic compounds Quaternary ammonia
Alcohols
Denature proteins, solubilize membranes (can be used as antiseptics and disinfectants)
Aldehydes
Chemically modify proteins and nucleic acids
Glutaraldehyde
2% solution used on medical instruments that are heat sensitive
Formaldehyde
Gas used to fumigate (especially areas with airborne viruses, cruise ship)
Orthophthaladehyde
OPA, newer aldehyde, has shorter contact time
Biguanides
Adhere to skin and mucous membranes
Biguanides are a type of…
Antiseptic
Biguanides target…
Membranes for destruction
Chlorhexidines
Type of biguanide, antiseptic ointment or solution
- Surgical scrubbing
- Mouthwash
- Skin abrasions
Ethylene oxide
For use on substances that can not withstand autoclaving, used on surgical garbs
What does ethylene oxide do?
It is highly oxidative, destroys DNA
Halogens
Target proteins, react with organic molecules to form toxic substances
Examples of halogens
Chlorine
Wescodyne
Iodine- not effective against endospores and Pseudomonas species (only effective against what is common)
Ozone
Target proteins, oxidative agent
Ozone is used for..
Drinking water and wastewater (usually the last step in many water treatment plants)
Peroxygens
Target proteins
Oxidizing agents
Examples of peroxygens
Hydrogen peroxide (H2O2) Peracertic acid
Phenolic compounds
Dissolve membranes
Denature proteins
-Lysol
Quaternary ammonia compounds
Research labs and food preparation areas
Cationic detergents
What do quats do?
Bind to negatively-charged membrane lipids
Chemicals that target cytoplasmic membrane
Biguanides
Phenolics
Quats
Chemicals that target DNA
Ethylene oxide
Aldehydes
Chemicals that target proteins
Alcohols Aldehydes Halogens Metals Ozone Peroxygens Phenolics
