Chapter 6: Bacillus and Clostridium

Question 1

Describe the organisms Bacillus and Clostridum

Answer 1

Gram-positive spore-forming rods

Question 2

Does Bacillus or Clostridum like oxygen?

Answer 2

Bacillus is aerobic while Clostridum multiply in anaerobic environment

Question 3

What is the ONLY bacterium with a capsule composed of protein?

Answer 3

Bacillus Anthracis

Prevents phagocytosis

Question 4

How do humans contract Bacillus anthracis/

Answer 4

Direct contact with infected animals or soil
Handling infected animal products - hides or wool, drums, rugs,

Human-human contact NEVER been reported

Question 5

Bacillus anthracis forms a spore which is resistant to what?

Answer 5

very stable and resistant to drying, heat, UV light, disinfectants, and can survive dormant in the soil for decades

Question 6

The germination and expression of plasmid encoded virulence factors of Bacillus anthracis is found on what plasmids?

Answer 6

pXO1 and PXO2

Question 7

What is pXO1 and pXO2 regulated by?

Answer 7

an increase in temperature to 37C, CO2, and serum proteins

*Spores only formed when introduced into the host

Question 8

Where can Bacillus anthracis germinate?

Answer 8

skin abrasions, lungs, GI

Question 9

What is a malignant pustule?

Answer 9

Exotoxin released by Bacillus anthracis causes a localized tissue necrosis, painless round black lesion with a rim of edema

Question 10

What is Woolsorter’s disease?

Answer 10

Pulmonary anthrax
Spores taken up by Mo in the lungs and transported to hilar and mediastinal LNs where they germinate
Mediastinal hemorrhage occurs
Pleural effusions

Question 11

What three proteins does the exotoxin encoded on plasmid pXO1 have?

Answer 11

Edema factor: EF - active A subunit, increases cAMP, Impaires neutrophil function and massive edema

Protective antigen (PA): promotes entry of EF into phagocytic cells

Lethal factor (LF): zinc metalloprotease that inactivates protein kinase. Stimulates TNF-a and IL-1b release from Mo

Question 12

What does pXO2 encode?

Answer 12

three genes necessary for the synthesis of poly-glutamyl capsule
Inhibits phagocytosis of vegetative bacteria

Question 13

How does Bacillus cereus differ from Bacillus anthracis?

Answer 13

motile, non-encapsulated and resistant to penicillin

Bacillus anthracis is NON-motile

Question 14

What does Bacillus cereus cause?

Answer 14

food poisoning (nausea, vomiting, and diarrhea)

Question 15

What enterotoxins can Bacillus cereus secrete?

Answer 15

Heat-labile toxin: Nausea, abdominal pain, diarrhea lasting 12-24 hrs

Heat-stable toxin: severe nausea, vomiting, and limited diarrhea

Question 16

The toxin released by Clostridium botulinum causes what?

Answer 16

rapid fatal food poisoning
Blocks the release of ACh from presynaptic nerve terminals in the ANS and motor endplates
Causes flaccid muscle paralysis

Question 17

Adult Botulism

Answer 17

Transmission: Smoked fish or canned veggies
S/S: b/l CN palsies causing double vision (diplopia), difficulty swallowing. general muscle weakness, sudden respiratory paralysis and death

Question 18

Infant Botulism

Answer 18

Transmission: Honey, contaminated food

S/S: constipated for couple of days, Difficulty swallowing, muscle weakness, Floppy babies

Question 19

Wound Botulism

Answer 19

Least common presentation of botulism
Puncture wounds
Similar to adult botulism except absence of prodromal GI symptoms and longer incubation period
Fever, Elevated WBC count

Question 20

Clostridium tetani causes what?

Answer 20

tetanus: disease that classically follows a puncture wound by a rusty nail or other skin trauma
Spores found in soil and animal feces
Germinated in necrotic tissue

Question 21

What is the exotoxin of Clostridium tetani?

Answer 21

tetanospasmin: causes sustained contraction of skeletal muscles

Question 22

How does tetany occur?

Answer 22

tetanus toxin taken up at NMJ and transported to CNS

Toxins act on inhibitory Renshaw cell interneurons: prevents release of GABA and glycine (inhibitory NT)

Question 23

Symptoms of tetany

Answer 23

Severe muscle spasms, lockjaw/trismus
Grotesque grinning expression = risus sardonicus
Mortality high after lockjaw

Question 24

Describe Clostridium perfringens

Answer 24

Spores found in soil
Matures in anaerobic conditions
Produces gas

Question 25

What are the 3 classes of infection with Clostridium perfringens?

Answer 25

Cellulitis/wound infection
Clostridial myonecrosis
Diarrheal illness

Question 26

Cellulitis/wound infection by Clostridium perfringens

Answer 26

Necrtoic skin is exposed, organisms grows and damages local tissue. Palpation reveals a moist spongy, crackling consistency to the skin due to pockets of gas (crepitus)

Question 27

Clostridial myonecrosis by Clostridium perfringens

Answer 27

Secretes exotoxins that destroy muscle adjacent to wound entry
Ferment carbs, resulting in gas formation
Pockets of gas within muscles and subQ tissue
Thin blackish fluid exudes from skin
Fatal unless treated early

Question 28

Diarrheal illness by Clostridium perfringens

Answer 28

Spores can germinate in foods (meat, poultry, gravy)
Ingestion of large amounts can lead to toxin in gut
Watery diarrhea

Question 29

What is responsible for antibiotic-associated pseudo-membranous colitis?

Answer 29

Clostridium difficile

Severe diarrhea, abdominal cramping and fever

Question 30

What can follow the use of broad spectrum antibiotics that leads to diarrhea?

Answer 30

Antibiotics wipe out part of normal intestinal flora, allows Clostridium difficile to superinfect to colon
Releases its exotoxins

Question 31

What toxins does Clostridium difficile release?

Answer 31

Toxin A - causes diarrhea

Toxin B - cytotoxic to the colonic cells

Question 32

Pseudomembranes

Answer 32

red inflamed mucosa and areas of white exudate on the surface of the large intestine