Exam 4: Antiseptics and Disinfectants

Question 1

What is sterilization?

Answer 1

The destruction of all forms of life, especially microorganisms

Question 2

What is disinfectant?

Answer 2

An agent that destroys pathogenic organisms, usually on inanimate objects
Reducing the pathogen load by 99.9999%

Question 3

What is antiseptic?

Answer 3

An agent that prevents or arrests the development of microorganisms on living tissue

Question 4

Rank the relative resistance to disinfection of various etiologic agents from least resistant to most resistant

Answer 4

Medium-sized lipid viruses (enveloped)
Vegetative bacteria
Fungi
Small non-lipid viruses (non-enveloped)
Tubercle bacilli
Coccidial oocysts
Protozoal cysts
Bacterial spores
Prions

Question 5

How effective is dry heat as a sterilization method?

Answer 5

Generally inferior to moist heat
Proper time and temperature is 160 deg. C for 2 hours or 170 deg. C for 1 hour
Dry heat coagulates the proteins in any organism, causes oxidative free radical damage, causes drying of cells
Limited number of items can withstand the temperatures

Question 6

How effective is boiling water as a sterilization method?

Answer 6

Kills vegetative cells of bacteria and fungi, protozoan trophozoites, and most viruses within 10 minutes at sea level
Temperature cannot exceed 100 deg. C; steam carries excess heat away
Boiling time is critical
Water require longer boiling time
Bacterial spores, protozoan cysts, and some viruses can survive boiling

Question 7

How effective is autoclaving as a sterilization method?

Answer 7

The standard sterilization used
Moist heat is applied under pressure
The increased pressure allows steam to be superheated
Duration varies- 15-30 minutes

Question 8

What are the risks associated with the use of ethylene oxide as a sterilization agent?

Answer 8

It is toxic, carcnogenic, and explosive

This requires special equipment and venting for proper use

Question 9

Why is peroxide plasma sterilization replacing ethylene oxide as the preferred method of sterilizing heat sensitive items?

Answer 9

Though it requires special equipment, it is considered to have a larger safety margin than ethylene oxide

Question 10

What size micron filter should be used to filter fluids in order to remove bacteria and fungi? What etiologic agents will filtration not remove?

Answer 10

0.22 and 0.45 μm pores should be used to remove bacteria and fungi
This will not remove spirochetes, mycoplasmas, and viruses

Question 11

UV light is sometimes used in biocontainment hoods for sterilization/disinfection. What are its limitations?

Answer 11

It is only effective for “line of sight” surface disinfection
It does not penetrate anything
Directly looking at UV light can damage the retina and cornea

Question 12

Does gamma ray sterilization leave a treated object radioactive?

Answer 12

The source of gamma ray is radioactive, but the object does not become radioactive

Question 13

Name the only high-level disinfectant in common use in veterinary practice

Answer 13

Glutaraldehyde 2%

Question 14

Contrast which bacteria are killed for a high-level versus low-level disinfectant

Answer 14

High-level disinfectant: kill bacterial spores and everything below that
Low-level disinfectant: effective on vegetative microorganisms but not spores or tubercle bacilli

Question 15

How does an iodine tincture differ from an iodine solution?

Answer 15

Iodine tincture implies there is alcohol in the solution

Iodine solution is just iodine and potassium iodine in water, no alcohol

Question 16

Povidone iodine solutions can be used for use as wound lavage solution over a wide range of v/v dilutions. Name the upper and lower limits of that range.

Answer 16

Solution in concentrations of 0.1-1% used to lavage wounds (10% solution diluted 1:10 to 1:100 v/v in water)

Question 17

Name an antiseptic restricted to use on skin that accumulates with time having a long residual activity

Answer 17

Chlorhexadine scrub formulation

Question 18

How does EDTA enhnace the activity of an antibiotic used topically?

Answer 18

It damages the cell membrane and a synergistic action occurs

Question 19

Pseudomonas and yeast are unusually sensitive to what common household food item that can be used as an antiseptic?

Answer 19

Distilled white vinegar which contains acetic acid

Question 20

What agents are often used in foot baths for cattle and sheep?

Answer 20

Zinc sulfate
Copper sulfate
Formalin

Question 21

How does dirt and manure affect the efficacy of these foot baths?

Answer 21

They lower the efficacy, so keeping them clean is important

Question 22

What v/v dilution of chlorhexadine is used as an antiseptic, particularly to lavage wounds?

Answer 22

1:40 v/v dilution is used where it is considered non-toxic to tissues

Question 23

What are the ingredients found in a Modified Dakin’s antiseptic solutions?

Answer 23

Full strength is 0.5% sodium hypochlorite (a 1:10 v/v diltution of 5% sodium hypochlorite (bleach) in water)

Question 24

Name 2 agents historically used as wound antiseptics that are now known to be too toxic to the tissue for this use

Answer 24

Hydrogen peroxide

Benzoyl peroxide

Question 25

What category of disinfectant should be used cautiously especially around cats?

Answer 25

Phenols

Question 26

Name 2 disinfectants that maintain their activity in organic debris?

Answer 26

Phenols

Chlorhexadine

Question 27

In what disease conditions is silver sulfadiazine commonly used?

Answer 27

It’s effective against pseudomonas and some yeast

Used in burns, wounds and otically

Question 28

Discuss alcohol as a disinfectant, including its categorization (low, intermediate, high), relative onset, and types of alcohol (isopropyl, ethyl, and methyl alcohol) and concentration percentages for best efficacy.

Answer 28

A low to intermediate disinfectant, but very effective against most vegetative bacteria and many enveloped viruses
Rapidly kills susceptible organisms
Types are ethanol and isopropyl
70% alcohol is considered optimal. 100% is not very effective, so you want to add some water
Alcohol works by denaturing protein
Presence of water assists with killing action

Question 29

Describe chlorhexadine

Answer 29

Low-level disinfectant, good against gram + bacteria but less effective against gram -.
Disrupts cell membrane and maintains most of its activity in presence of organic matter- leave in contact for at least 5 minutes

Question 30

Describe benzoyl peroxide

Answer 30

Active only against gram + bacteria
—We use it mainly for staph pyoderma
Too toxic for tissues
The most repository of the skin antiseptics

Question 31

Describe hydrogen peroxide

Answer 31

An oxidizer that produces destructive hydroxl free radicals that attack membranes, DNA and other essential cell components
Hydrogen peroxide solution= low to intermediate level disinfectant
Accelerated hydrogen peroxide (AHP)= can act as high level disinfectant
Can be used to clean intact skin but is too toxic as an antiseptic

Question 32

Describe EDTA

Answer 32

A chelator of di- and tri- valent cations
By damaging bacterial cell membrane, a synergistic action occurs with many abx
Commonly used in otitis externa, multi-resistant bladder infections as an infusion and for wounds and fistulas

Question 33

Describe povidone iodine

Answer 33

Increased solubility, improved wetting properties, less toxic to tissues and therefore the only iodine recommended for use in wounds
Least residual activity of all the antiseptics

Question 34

Identify the 9 common disinfectant mistakes

Answer 34

1. Eyeballing disinfectant mixtures
2. Failing to reach designated contact time
3. Confusing sanitized with disinfection
4. Not knowing the shelf-life of the disinfectant being used
5. Topping off diluted disinfectant bottles, rather than starting each time with a cleaned bottle and fresh batch
6. Mixing cleaning chemicals
7. Spraying a surface then wiping it with a dry cloth
8. Not giving or receiving product-specific training to veterinary team members
9. Not getting buy-in from team members on a switch to a new product