Clostridia

Question 1

Clostridium general characteristics

Answer 1

Strict anaerobe
Gram-positive rods
Produces Endospores
Produces proteinaceous toxins that are responsible for disease symptoms

Question 2

Clostridium species

Answer 2

C difficile
C perfringens
C botulinum
C tetani

Question 3

Spores

Answer 3

Few bacteria have the ability to form endospores
Metabolically inactive state in which organisms can remain viable for hundreds of years
Resistant in adverse conditions

Question 4

What causes spore induction

Answer 4

Unfavorable environmental conditions (heat, dry, radiation - things that would cause nutrient depletion)

Question 5

When do spores germinate?

Answer 5

When conditions become favorable for vegetative growth

Question 6

What bacteria can form endospores?

Answer 6

Bacillus and Clostridium

Question 7

C. difficile characteristics

Answer 7

Not easy to culture
Spores are resistant to antibiotics
Currently the leading cause of nosocomial diarrhea
Pseudomembranous colitis
Secretes C difficile toxins A and B

Question 8

Pseudomembranous colitis

Answer 8

Yellow plaques containing fibrin and cellular debris in ulcers of colonic mucosa

Question 9

C difficile Toxin A

Answer 9

Enterotoxin - fluid production and damage to the mucosa

Question 10

C difficile Toxin B

Answer 10

Cytotoxin - rounding of tissue-culture cells

Question 11

C perfringens characteristics

Answer 11

Found in soil and intestinal tracts of animals
Environmental pathogen found in every soil except Sahara desert sand
Major pathogen of wound infections (especially war wounds)
Both local damage and systemic effects

Question 12

C perfringens tissue infections

Answer 12

Severe trauma introduces spores from environment, which germinate under anaerobic conditions, compromsed blood supply, calcium ions, and availability of peptides and amino acids. All of these occur with tissue damage. Produces toxins that cause cellulitis leading to gangrene

Question 13

Gangrene

Answer 13

A necrotizing, gas forming process of muscle atrophy associated with systemic signs of shock. Caused by C perfringens

Question 14

Treatment of C perfringens

Answer 14

Surgical removal of infected muscles.
Antibiotics to control infection (amputation still necessary)
Can also introduce antitoxin from horses (little effect), or high oxygen concentration (rarely works)

Question 15

Other than gangrene, C perfringens can also cause…

Answer 15

Food poisoning.
Produces an enterotoxin in intestines of people who have consumed contaminated meat.
Diarrhea in 12-24 hours
Self-limiting and dissapears in 1-3 days

Question 16

C. botulinum characteristics

Answer 16

Found in soils and marine sediments
Produces heat-resistant spores that often survive food processing (canned food)
Causative agent of botulism
Produces toxins
Bioweapon threat

Question 17

C botulinum toxins

Answer 17

Produces 8 neurotoxins: A-G

Amongst the most poisonous substances known

Question 18

Most common C botulinum toxins in humans

Answer 18

A, B, E

Question 19

Lethal dose of C botulinum toxins

Answer 19

< 1ug

Question 20

C botulinum toxin mechanisms

Answer 20

• Prevents release of ACh

- Zinc metalioprotease cleaves proteins involved in docking neurotransmitter vesicles

Question 21

C botulinum toxin effects

Answer 21

Flaccid paralysis within 12-36 hours

Cranial nerves are effected first, and then it descends causing respiratory failure

Question 22

3 Types of Botulism

Answer 22

Food-bourne
Wound
Infant

Question 23

Food-bourne botulism

Answer 23

Ingestion of preformed toxin in foods that have not been canned properly

Question 24

Wound botulism

Answer 24

Rare
Systemic spread of toxin produced by organisms inhabiting wounds
Caused by trauma, surgery, subcutaneous heroin injections, and sinusitis from intranasal cocaine abuse

Question 25

Infant botulism

Answer 25

Intestinal colonizaiton of organisms in infants younger than 1 year old Slow onset Favorable outcome Hypotonic ("floppy") state

Question 26

Botulism Treatment

Answer 26

Current mortality rate with care is about 25% A trivalent antitoxin (isolated form horses) should be administered asap Some muscles are permanently damaged

Question 27

Why aren't antibiotics necessary in treating botulism?

Answer 27

We're treating the toxin, not the organism

Question 28

Clostridium tetani characteristics

Answer 28

Ubiquitous in the GI tract of humans and animal Also in soil Spores resistant to environment Infection usually associated with traumatic wounds Leads to tetanus

Question 29

Tetanus cause

Answer 29

Germination of spores and production of toxin (tetanospasmin). Can be caused by wounds or neonatal contamination of umbilical cord at delivery

Question 30

Tetanospasmin

Answer 30

Major toxin of tetanus Responsible for all symptoms 150 kDa protein Made of heavy and light chain connected by a disulfide bond (nontoxic individually)

Question 31

Tetanospasmin mechanism

Answer 31

Attaches to peripheral nerves near the wound and travels to cranial nerve nuclei Inhibits neurotransmitter release for normal inhibitory input (GABA) Results are reflex spasms and spastic paralysis

Question 32

Tetanus characteristics

Answer 32

Trismus (lockjaw) in 80% of cases Descends to neck and back muscles and produces rigidity of abdomen and stiffness of extremities Leads to respiratory failure form paralysis of chest muscles

Question 33

Treatment and Prevention of Tetanus

Answer 33

Completely preventable with DPT vaccine Human globulin is sometimes given as a passive immunization in "tetanus-prone wounds" Antitoxin should be administered immediately Antibodies are not produced due to low amounts of toxin pressent Surgical debridement