Chapter 11: Gnotobiotics

Question 1

What does the term “gnotobiotics” mean?

Answer 1

Well-known life

Question 2

True or False

A germ-free animal is a type of gnotobiote

Answer 2

True

Question 3

True or False

Axenic rats are not available commercially; they must be developed within the individual animal facility.

Answer 3

False

Question 4

Identify at least four sterilization methods used to support gnotobiotic systems

Answer 4

1- steam autoclaving
2- dry heat
3- peracetic acid
4- ethylene oxide

Question 5

Define “axenic animal”

Answer 5

An animal free of all demonstrable microorganisms

Question 6

What is different about an axenic animal’s cecum from other animals?

Answer 6

The axenic animal has a greatly enlarged cecum

Question 7

Are all gnotobiotes axenic? Why or why not?

Answer 7

No. Axenic or germ-free animals are only one type of gnotobiote. Defined flora animals are also gnotobiotes.

Question 8

Describe the process of embryo transfer for deriving an axenic animal.

Answer 8

The embryos from a superovulated mother are removed, washed, and transferred to the reproductive tract of a psuedopregnant axenic female in a surgical isolator

Question 9

Why should you use a foster mother whose coat color is different from the donor mother in a hysterectomy derivation to produce axenic animals?

Answer 9

To make sure the fostered pups are distinguishable from the foster mother’s own litter

Question 10

What is a Schaedler cocktail and why is it given to axenic animals?

Answer 10

The cocktail of normal symbiotic (nonpathogenic) intestinal bacteria is given to normalize the gut physiology and anatomy

Question 11

What is a transfer sleeve?

Answer 11

A flexible plastic tube of the same diameter as the entry port and the supply cylinder

Question 12

Which of the following are true of axenic animals as compared to animals with normal micro flora? Choose all that apply to axenic animals.
A- they have lower white blood cell counts
B- their cecal content is more acidic
C- their cholesterol level is generally higher
D- their thymus is smaller
E- their cecum is smaller
F- their intestinal walls are thicker

Answer 12

A- they have lower white blood cell counts
C- their cholesterol level is generally higher
D- their thymus is smaller

Question 13

How do litter sizes compare between axenic and defined flora animals?

Answer 13

Axenic animals generally have smaller litters

Question 14

Axenic animals require more vitamins ________ and _________, and have lower requirements for vitamins ________ and _________.

Answer 14

K and B

A and E

Question 15

What is a major advantage of flexible isolators compared to rigid isolators?
A- They offer better protection against contamination
B- They are less expensive to manufacture
C- They are easier to disinfect and sterilize
D- They are longer-lasting

Answer 15

B- They are less expensive to manufacture

Question 16

Animals that have a normal intestinal flora but are free of particular organisms are called:
A- defined flora
B- axenic
C- normal
D- specific pathogen free

Answer 16

D- specific pathogen free

Question 17

Which of the following is NOT an appropriate sterilization method for gnotobiotic systems?
A- peracetic acid
B- steam autoclaving
C- carbon dioxide
D- membrane filtration of liquids

Answer 17

C- carbon dioxide

Question 18

The most basic requirement for an isolator is that it must be:
A- impervious
B- transparent
C- rigid
D- impact-resistant

Answer 18

A- impervious

Question 19

What function does a transfer sleeve serve?
A- to control the speed of the transfer of material into the isolator
B- to sterilize the materials before placing them in the isolator
C- to connect the supply cylinder to the isolator entry port
D- to remove airborne microorganisms from the room air

Answer 19

C- to connect the supply cylinder to the isolator entry port

Question 20

Which vitamins are required in lesser quantities in axenic animals?
A- B vitamins and vitamin K
B- vitamin A and vitamin E
C- vitamin C and vitamin D
D- vitamins B1 and B12

Answer 20

B- vitamin A and vitamin E

Question 21

What is the advantage of giving gnotobiotics a cocktail containing normal intestinal flora?
A- it makes their decal content more acidic
B- it protects them from infection
C- it serves to normalize the gut physiology and anatomy
D- it helps regulate their immune system

Answer 21

C- it serves to normalize the gut physiology and anatomy

Question 22

Why are foundation colonies generally maintained in the defined flora state instead of in the axenic state?
A- to maintain genetic integrity
B- to optimize litter size
C- to study the progression of infection
D- to improve immunity of the animals

Answer 22

B- to optimize litter size

Question 23

Animals that were originally germ-free but were given a known group of bacteria are called known as what type of animals?
A- axenic
B- defined flora
C- specific pathogen free
D- normal

Answer 23

B- defined flora

Question 24

Which statement is true of axenic animals as compared to animals with normal microflora?
A- their decal content is more acidic
B- they have lower white blood cell counts
C- their cholesterol level is generally lower
D- their thymuses are bigger

Answer 24

B- they have lower white blood cell counts