Sterilization and Disinfection - Venke

Question 1

What type of facility do certain organisms such as Mycobacterium tuberculosis, Bacillus anthracis and Yersinia pestis be exclusively handled inside?

Answer 1

bio-safety level 3 facility

Question 2

What is sterilization? What is a common process used for sterilization?

Answer 2

Sterilization in complete killing of all forms of infection including spores. This can be achieved only by autoclaving where the sample to be sterilized at 15 pounds pressure for 15 minutes at 1200C

Question 3

what is disinfection? are all forms of organisms killed during disinfection?

Answer 3

Disinfection is a chemical treatment that kills vegetative organisms. However spores are not killed by disinfection.

Question 4

What is the name for disinfectants that are safe to be used on skin?

Answer 4

antiseptics

Question 5

Which disinfectants damage the lipid membrane of microbes? (3)

Answer 5

1. alcohol
2. detergents (Bezylkonium chloride-common skin antiseptic)
3. phenol compounds (protect against lipids and proteins)

Question 6

What are disinfectants that alter proteins? (7)

Answer 6

1. chlorine (causes inactive sulfides through cross links) ex: bleach has sodium hyper chloride
2. iodine (inactivates sulfhydryl containing enzymes)
3. heavy metals (inactivate sulfhydryl containing enzymes)
4. hydrogen peroxide (inactivate sulfhydryl containing enzymes)
5. formaldehyde (alkylates amino and hydroxyl groups in both proteins and nucleic acids )
6. glutaraldehyde (alkylates amino and hydroxyl groups in both proteins and nucleic acids –> more effective then formaldehyde)
7. ethylene oxide (has hydroxyethyl groups that alkylates amino and hydroxyl groups) –> used to sterilize surgical equipment

Question 7

Which disinfectants modify DNA? (2)

Answer 7

1. crystal violet (positive charge binds to negatively charged DNA to inactivate)
2. malachite green (positive charge binds to negatively charged DNA to inactivate)

Question 8

What three things does an aseptic environment have?

Answer 8

1. laminar flow
2. HEPA filter
3. UV light

Question 9

What physical agents modify DNA?

Answer 9

1. moist heat (break non-covalent hydrogen bonds) –> autoclave: 120 degrees, 15 pounds of pressure for 15 minutes
2. dry heat–> used to sterilize glass
3. pasteurization
4. filtration (filters endotoxin. used to sterilize protein solutions because viruses and bacteria are too large to go through)
5. UV radiation (causes thymine dimerization) (cannot kill spores)
6. x-rays: capable of producing hydroxyl radicals –> breaks DNA

Question 10

What is used to sterilize surgical instruments that are sensitive to heat sterilization?

Answer 10

ethylene oxide

Question 11

What kills all forms of microorganisms?

Answer 11

autoclaving