Module 5.4 Gram Positive Spore forming Anaerobic Rods

Question 1

List some key characteristics of the Clostridium species.

Answer 1

• large spore-forming rods
• widespread in env. (soil)
• commensals of the large bowel
• rapid multiplication
• simple growth requirements
• similar to bacillus anthracis but anaerobic

Question 2

Case Report:
- 3 days old beef calf
- hemorrhagic diarrhea, affecting multiple calves
- dehydrated, off feed, unresponsive to treatment
- died 1-2 days after onset of clinical signs
- PCR for toxin type, gram stains, ELISA
- small intestine had enteritis, necrotizing, acute
What is a common cause of death relayed to these signs?

Answer 2

Clostridium perfringens type C

Question 3

Clostridium perfringens 1-PR/OPP

Answer 3

• fecal contamination
• fastest growing bacterium
• PCR divides into 7 types (A-G)
• most strains are intestinal commensals

Question 4

Clostridium perfringens type A

Answer 4

• intestinal commensals
• two commonly seen diseases: hemorrhagic necrotizing enteritis in dogs and foals (NetF toxin), abomastitis in calves

Question 5

Clostridium perfringens type B and C

Answer 5

Type B:
- never reported in Canada
- lamb dysentery

Type C:
- neonatal hemorrhagic enterotoxemia
- hemorrhagic enteritis
- rare in Canada
- B-toxin
- affects farm species

Question 6

Clostridium perfringens type D and E

Answer 6

Type D:
- pulpy kidney
epsilon toxin which liquifies kidney
- no enteritis

Type E:
- hemorrhagic enteritis
- iota toxin

Question 7

Clostridium perfringens type F and G

Answer 7

Type F:
- most common
- food poisoning in humans
- protein rich food
- Cpe enterotoxin

Type G:
- necrotic enteritis in broiler chickens (NetB toxin)

Question 8

Treatment and control of Clostridium perfringens

Answer 8

• antimicrobial prophylaxis in broilers
• hygiene
• debriding wound
• antibiotics

Question 9

Clostridioides difficile 1-PR-Z

Answer 9

• severe colitis in humans and horses
• fatal Typhlocolitis (cecum and colon) in horse
• antibiotics disrupt anaerobic large bowel flora and Clostridioides difficile loses competitive exclusion, causing uncontrolled proliferation of C difficile which survives as a spore

Question 10

What is the pathogenicity of Clostridioides difficile?

Answer 10

• transmission via spores
• pass through the stomach and induce germination
• vegetative cells produce 2 toxins: Toxin A which is enterotoxin/cytotoxin and Toxin B a cytotoxin
• major hospital acquired infections

Question 11

Diagnosis/treatment/control of Clostridioides difficile?

Answer 11

• glutamate dehydrogenase (GDH) ELISA (toxin ELISA)
• fecal flora transplant
• beware of antibiotic use

Question 12

What are the three toxin types of clostridia?

Answer 12

• enterotoxin = toxins formed in the intestines and absorbed into the blood stream producing a generalized toxemia
• histotoxic clostridia = gas gangrene (wound infections) producing clostridia which are invasive, species that cause tissue damage
• neurotoxic clostridia = non-invasive and colonize the host to a very limited extent

Question 13

Clostridium chauvoei 1-PR

Answer 13

• Blackleg
• acute, infectious, necrotizing myositis in young calves in summer

Question 14

Pathogenesis of Clostridium chauvoei

Answer 14

• transmission by ingestion of spores
• they reach the blood from intestine via the liver, then liver to muscle
• activation of latent spores by anoxia
• locally necrotizing myositis, systemic toxemia
• rapid death

Question 15

Clostridium chauvoei (Blackleg) diagnosis?

Answer 15

• swollen legs, gas under the skin
• anaerobic culture
• fluorescent antibody stain
• PCR

Question 16

Clostridium tetani 1-PR

Answer 16

• rod terminal spores
• tennis-racket shape
• deep wounds
• particular association with horse manure
• survives excellently as spores
• causes contractions and spasms

Question 17

Virulence factors of Clostridium tetani?

Answer 17

• associated with local infection that then spreads to the CNS
• production of tetanospasmin which is a toxin
• tetanolysin = local cytolytic activity

Question 18

Pathogenesis of Clostridium tetani?

Answer 18

1. Production of toxin at infection site
2. Toxin migrates through axon to CNS
3. Toxin migrates to inhibitory neuron
4. Toxin in inhibitory neuron endplate inhibits release of inhibitory transmitters (GABA and glycine)
5. Motor neurons can fire stimulatory signals uninhibited causing spasm

Question 19

Treatment and prevention of Clostridium tetani (Tetanus)

Answer 19

• keep animal in calm, darkness, silence
• muscle relaxants, artificial respiration
• vaccination and toxoid

Question 20

Clostridium botulinum 2-PR

Answer 20

• most potent toxin known
• flaccid paralysis
• preformed toxin produced under anaerobic spoilage of decaying animals/plants
• intoxication

Question 21

Clostridium botulinum virulence factors

Answer 21

• botulinum toxin is THE most powerful toxin
• 1ug will kill a person
• zinc endopeptidase = homology to tetanospasmin

Question 22

What is the mechanism of action behind botulinum toxin?

Answer 22

• targets the cholinergic cells
• blocks presynaptic release of acetylcholine
• location of effect = peripheral

Question 23

How do we diagnose Clostridium botulinum? (Botulism)

Answer 23

• Toxin test (mouse>ELISA)
• PCR for toxin genes
• clinical (causes a wasp waist in mice via diaphragmatic paralysis)

Question 24

What is the pathogenesis of tetanus in a horse? (causative agent, route of infection, virulence factor, disease and clinical signs)

Answer 24

• Clostridium tetani
• particular association with horse manure
• infects deep wounds then makes its way up to the CNS and inhibits the inhibitory transmitters like GABA so that the motor neurons fire spastically
• causes contractions and spasms

Question 25

What is the pathogenesis of botulism in a cow? (causative agent, route of infection, virulence factor, disease and clinical signs)

Answer 25

- Clostridium botulinum - usually produced under anaerobic spoilage of decaying animals/plants - intoxication usually occurs via ingestion of spoiled feed - the toxin blocks the presynaptic release of acetylcholine, causing flaccid paralysis

Question 26

What is the pathogenesis of blackleg in a steer? (causative agent, route of infection, virulence factor, disease and clinical signs)

Answer 26

- Clostridium chauvoei - lives in the soil and intestine as a latent spore and activates in anoxic conditions - transmission occurs via ingestion of the spores, they travel through the blood to eventually reach muscle and become active in anoxic environments - rapid proliferation occurs and causes swollen legs, gas under the skin and a change in colour - death typically occurs rapidly

Question 27

What is the pathogenesis of pulpy kidney in a goat? (causative agent, route of infection, virulence factor, disease and clinical signs)

Answer 27

- Clostridium perfringens type D - most strains are normal commensals in the gut, Type D is found in sheep and goats - known as over eating disease because with a higher starch intake it provides a good environment for overgrowth of Clostridium perfringens Type D - produces epsilon toxin that liquifies the kidney - it is unlike the other Clostridium perfringens strains because it does NOT cause enteritis

Question 28

Is the tetanus toxoid vaccine effective?

Answer 28

Yes!

Question 29

Are the blackleg vaccines effective?

Answer 29

Yes! You can vaccinate via parenteral immunization of inactivated bacteria and toxoid.