Lecture 12 - Gram positive rods

Question 1

Describe each of the 4 Koch’s postulates

Answer 1

1. Microorganism must be found in abundance in all organisms suffering from the disease but not in healthy animals
2. Must be isolated from diseased organism and grown in pure culture
3. Should cause disease when reintroduced into healthy organism
4. Must be reisolated from the inoculated, diseased experimental host and identified as identical to original

Question 2

3 characteristics of Corynebacterium diphtheriae

Answer 2

Gram positive
No Spores
Rods (bacilli)

Question 3

Where is Corynebacterium diphtheriae found?

Answer 3

Skin, upper respiratory tract, GI tract

Question 4

What is the major mode of action by Corynebacterium diphtheriae?

Answer 4

A-B exotoxin blocks protein production in cells by EF-2

Question 5

How does Diptheria work?

Answer 5

It does not enter the blood stream. It is a local infection that releases its exotoxin into blood causing systemic disease. Toxin production only occurs when the bacillus is itself stably infected by a bacteriophage carrying the genetic info for the toxin.

Question 6

What must occur before Corynebacterium diphtheriae can release its toxin?

Answer 6

It must be infected by a bacteriophage carrying the genetic info for the toxin.

Question 7

Where does the B subunit bind on the A-B exotoxin for diptheria?

Answer 7

It binds to heart and nerve cells

Question 8

How is diptheria transmitted?

Answer 8

Respiratory droplets. Maintained in population by asymptomatic carriage in Throat

Question 9

The infection of diptheria produces what?

Answer 9

thick, gray-white, adherent exudate called pseudomembrane. It is difficult to dislodge without making underlying tissue bleed.

Question 10

What are the main tissues affected in diptheria

Answer 10

Affects upper respiratory tract, cardiac tissues and can cause heart damage.

Question 11

What is treatment for diptheria

Answer 11

Early administration of diptheria anti-toxin to neutralize exotoxin
Toxoid can be used to immunize people before the infection

Question 12

What is a toxoid:

Answer 12

has been modified so that it can no longer cause pathology but is still immunogenic

Question 13

T or F, spores are always G negative

Answer 13

False. Some are G+, never G-

Question 14

What are the two bacteria that we talked about as spore formers?

Answer 14

Clostridium and Bacillus

Question 15

Physiologic makeup of a spore

Answer 15

Inner membrane
Large peptidoglycan cortex
Thick keratin-like protein coat

Question 16

3 characteristics of Clostridium (oxygen dependence, gram stain, spores or no spores)

Answer 16

Obligate Anaerobic
G+ Bacilli
Spore-forming

Question 17

What type of exotoxin do C. tetani and C. botulinum have and what cells do they attack?

Answer 17

A-B exotoxins

Attack nerves

Question 18

C. tetani is also called:

Answer 18

Tetanus or spastic paralysis

Question 19

Difference in mode of infection for C. tetani and C. botulinum

Answer 19

Tetani:Spores typically infect and germinate in a deep wound where anaerobic conditions can be found
Botulinum: Spores or toxins are consumed in food

Question 20

C. tetani local or systemic?

Answer 20

They multiply locally and secrete A-B toxin into blood

Question 21

How does C. tetani target nerve cells?

Answer 21

A-subunit blocks neurotransmitter release at inhibitory synapses. causes prolonged muscle-spasms

Question 22

How does C. botulinum target nerve cells?

Answer 22

Blocks releases of Acetylcholine, prevents muscle contraction causing flaccid paralysis

Question 23

Another name for C. botulinum

Answer 23

Flaccid Paralysis or Botulism

Question 24

What type of nerves does C. botulinum attack?

Answer 24

Cholinergic nerves

Question 25

C. botulinum is most common in what age groups?

Answer 25

Infants

Question 26

C. perfringens can cause:

Answer 26

Gas gangrene and Food poisoning

Question 27

How does C. perfringens cause gas gangrene

Answer 27

Infect a dirty wound, huge number of exotoxins (mostly cytolytic) and spreading factors are released, infection spreads through surrounding tissue and kills cells

Question 28

Food poisoning in C. perfringens results from what?

Answer 28

eating food contaminated by C. perfringens spores that have germinated before eating. Not true food poisoning

Question 29

C. dificile causes what?

Answer 29

Pseudomembranous colitis which is also called “antibiotic colitis”. Occurs in individuals undergoing antibiotic therapy. Antibiotics clear up space in the existing flora for C. dificile to take their spot.

Question 30

2 characteristics of Bacillus anthracis

Answer 30

Gram positive

Spore forming

Question 31

where is Bacillus anthracis commonly found?

Answer 31

In soil, affects grazing animals that ingest spores

Question 32

3 types of anthrax in humans

Answer 32

1. Cutaneous anthrax - spore enters skin through cut
2. Pulmonary anthrax - airborne spores
3. GI tract anthrax - contaminated food

Question 33

What are the two A-B exotoxins released by B. anthracis

Answer 33

Edema toxin and Lethal toxin

Question 34

How is B. anthracis taken deeper into the body

Answer 34

Macrophages act as ‘taxi’s’ and take bacteria deeper into the body. Macrophages have difficulty killing bacteria.

Question 35

Do B. anthracis have a capsule

Answer 35

Yes