Chapter 5: Control of Microbial Growth - Chemicals (DDM, Phenols, Biguanides, Halogens)

Question 1

Are chemicals used for sterilization?

Answer 1

• no
• most are for disinfection

Question 2

What is the disk diffusion method? (3)

Answer 2

• disk of filter paper is soaked in chemical disinfectant
• Then placed on an agar plate that has been inoculated with bacteria
• The plate is incubated until bacteria grow

Question 3

What determines the effectiveness of the disinfectant in the disk diffusion method?

Answer 3

• zone of clearing determines effectiveness

Question 4

What are the different categories of disinfectants and antiseptics? (9)

Answer 4

• Phenols
• Biguanides
• Halogens
• Alcohols
• Heavy Metals
• Regular Soaps and detergents
• Quats
• Gaseous chemosterilizers
• oxidizing agents

Question 5

How do phenols work? (3)

Answer 5

• disrupt plasma membranes, denatures proteins
• bactericidal
• often mixed with other compounds to reduce toxicity

Question 6

Are phenols effective? (2)

Answer 6

• Very effective
• remain active long after application

Question 7

In what instance would phenols be used to disinfect?

Answer 7

• suitable to disinfect soiled surfaces (saliva, pus, feces)

Question 8

What are 3 examples of phenols?

Answer 8

• Original formulations of Lysol for household disinfection
• Hexachlorophene
• Triclosan

Question 9

When is hexachlorophene (phenol) used to disinfect? (3)

Answer 9

• useful against bacteria that causes skin infections in newborns
• disinfects surfaces in nursuries
• must be used with caution as it causes neurologial disorders

Question 10

In what products are triclosan (phenol) used in?

Answer 10

• some personal hygiene products like cosmetics and deodorant

Question 11

In lecture, What do Biguanides do to the human body?

Answer 11

• reduce the probability of sepsis

Question 12

Chlorhexidine is a biguanide. How does it work? (2)

Answer 12

• attacks plasma membrane
• bactericidal

Question 13

What microbes does chlorhexidine control the growth of?

Answer 13

• microbes on skin and mucous membranes

Question 14

Biguanides are used in surgical hand scrubs. Why? In other words, what are the characteristics of biguanides? (2)

Answer 14

-can persist for up to 6 hours
- only kills some viruses but does not destroy endospores

Question 15

How do Halogens work?

Answer 15

• destroy proteins and membranes

Question 16

Halogens are ____ and ____.

Answer 16

• disinfectants
• antiseptics

Question 17

Name 2 types of halogens.

Answer 17

• chlorine and iodine

Question 18

How does chlorine control microbial growth? (2)

Answer 18

• forms hypochlorous acid in water
• that acid is a strong oxidizing agent that denatures enzymes

Question 19

Give 2 examples of chlorine products. Are they sterilizers or disinfectants

Answer 19

• Household bleach (sodium hypochlorite) is an excellent disinfectant
• Chlorine dioxide - sterilizing gas

Question 20

Iodine is frequently used as an ____ (disinfectant/antiseptic)

Answer 20

antiseptic

Question 21

What are examples of iodine products? (3)

Answer 21

• tincture of iodine in an alcohol solution
• iodophore
• betadine

Question 22

What is an iodophore?

Answer 22

• linked to carrier molecule so that it is released slowly over time

Question 23

What is betadine used for?

Answer 23

• used as antiseptic on skin