Lecture 14- Physical and Chemical methods Flashcards
What is the destruction of all microorganisms on inanimate objects?
What type of method is this?
Sterilization
Physical method
What is the destruction of most microorganisms on inanimate objects?
What type of method is it?
Disinfection
Physical and Chemical method
What is the destruction of most microorganisms on living surfaces?
What type of method is it?
Antiseptic
Chemical method
What are the physical methods of microbial control?
Heating and radiation
Tell if these physical methods are sterilizing:
- Incineration
- Dry oven
- Steam pressure
- Boiling water
- Ionizing radiation
- Non-ionizing radiation
- Incineration= sterilization
- Dry oven= sterilization
- Steam pressure= sterilization
- Boiling water= non-sterilization
- Ionizing radiation= sterilization
- Non-ionizing radiation= non-sterilization
Give the order of resistance (most resistant to least) of these microbes:
- Gram-negative bact.
- Gram-positive bact.
- enveloped viruses
- naked viruses
- prions
- fungi
- bacterial endospores
- Prions
- Bacterial endospores
- Gram-positive bacteria
- Fungi
- Naked viruses
- Gram-positive bacteria
- Enveloped viruses
What are these terms:
- Bactericidal
- Bacteriostatic
- Bactericidal =
Destroys the bacteria
- Bacteriostatic
Prevents growth of bacteria
What are the 4 modes of action, chemicals have against microbes?
- Against bact. cell wall
- Against cytoplasmic membrane
- Against bacterial processes (DNA, RNA)
- Against bacterial proteins
How do agents that work against cell wall work?
What is the result?
- Block cell wall synthesis
- Digest the cell wall
Cell lyses
How do agents that work against the cytoplasmic membrane work?
- What is an example?
Bind lipid bilayer, make it leaky.
- Surfactants are amphiphatic
How do agents that work against bacterial processes work?
- What results?
Bind DNA to prevent transcription/translation
Bind ribosomes to stop peptide bonds from forming
- Can’t make proteins
How do agents that work against bacterial proteins work?
- What results?
Denature proteins (become inactive)
- loss of metabolism
What are the effects of heat and cold on bacteria?
Higher temperatures= bacteriocidal
Colder temps= bacteriostatic
What types of bacteria are most resistant to heat and least resistant?
most resistant= endospores
Least resistant= vegetative cells
How does ionizing radiation work?
What are examples?
Ejects electrons from atoms to form ions.
(Bad for mutations/proteins, changes organelles)
- Gamma and x-rays
How does non-ionizing radiation work?
What is an example?
Excites itoms to higher energy state.
- Forms weird bonds in DNA
- UV light
How does UV light affect DNA?
DNA absorbs UV and mutates due to formation of pyrimidine dimers
Are endospores more resistant to radiation than vegetative cells?
Yes, 10x more
What would you use Chlorine (bleach) (Chemical method) for?
C. Diff
What would you use iodine (chemical method) for?
Used as antiseptic before surgery
Microbicidal to all microbes
What would you use phenols for?
Microbicidal to all mirobes except Hep B.
Can’t be used as antiseptic (toxic)
What would you use Chlorhexidine (chemical method) for?
Kills bacteria, but not fungi/viruses
What would you use alcohols (chemical method) for?
Inactivate enveloped viruses, but not naked viruses
What would you use Hydrogen peroxide (chemical method) for?
Creates free radicals
Microbicidal to all mirobes
What would you use heavy metals (chemical method)?
Against microbes, but cause allergic reactions/toxic to humans
What would you use acids/alkalis for (chemical method)?
Prevents endospore germination
What would you use aldehydes (chemical method) for?
Microbicidial to microbes, but very unstable
