Bacillus/ Clostridium Flashcards
What kind of bacteria is Bacillus?
- Gram positive large rods
- Produce resistant spores
- Aerobes/ Facultative anaerobes (Clostridia are straight anaerobes)
- Grow rapidly producing colonies @ 24 hours.
- Can use many substrates to grow.
- Most are non pathogenic envrionmental organisms.
What are the main species of Bacillus of Veterinary Importance?
- B. anthracis- anthrax in cattle, man
- B. cereus- food poisoning, eye, soft tissue infection (man), Mastitis (cattle)
- Emetic form
- Diarrheal form
- B. liceniformis- sporadic abortion in cattle.
Species infection variation of Anthrax:
What species is highly susceptible?
Species moderately susceptible?
Species comparitvely resistant?
Species totally resistant?
- This is a worldwide endemic affecting virtually all mammals.
- Ruminants are highly susceptible and can develop a rapidly fatal septicemia.
- Pig, horses moderately susceptible.
- Carnivores are moderately resistant.
- Birds totally resistant.
Anthrax Epidemiology:
Most important factor in Anthrax persistance?
When do outbreaks occur?
How is infection acquired?
- **Endospore formation most important factor in persistance of anthrax in the environment and spread to other animals. **
- Endospores are EXTREMELY resistant and can survive in the environment (soil) for decades.
- Outbreaks usually occur in herbivores when pasture contaminated by spores…this is why ruminants are HIGHLY susceptible.
- These spores are brought to the surface by flooding, excavation, subsidence, earthworm activity.
- Infection is acquired by ingestion of spores either by inhalation or skin abrasian which is more common in man.
Describe the infectous process of B. anthrax.
- Endospores in the environment are brought to the soil surface (flooding, excavating, earthworm activity).
- These spores are ingested (grazing, drinking) or inhaled.
- The spores germinate inside the herbivore and multiply in the lymphatics and spleen.
- Vegetative forms (sexually active-asexual) are released in massive numbers into the ruminants blood in the final hours of its life.
- This causes an overwhelming septicemia and the animals begins to bleed from every orifice.
- Vegetative forms are shed at death in hemorrhagic excudate from the nose, mouth, anus.
- These vegetative form sporulate when exposed to O2 and become the notorious resistant endospores than can last for decades in the environment.
- Spores can infect cutaenously (man), pulmonary infection, gastrointestinal infection (infected meat, water, vegetables)
Anthrax Pathogenesis:
What are its virulence factors? Where are they encoded and how are they regulated?
- Virulence factors:
**a. poly-d-glutamic acid capsule
b. complex toxin**
2. Both virulence factors are encoded on plasmids.
3. The expression of these virulence factors are regulated by host temperature and CO2.
4. The poly-d-glutamic acid capsule inhibits phagocytosis.
5. The complex toxin consists of three anitgenic components ( protective antigen, edema factor, lethal factor) and the protective antigen acts as the binding moeity for edema/lethal factor.
Anthrax Pathogenesis continued:
Edema Factor- What virulence factor is this a component of? How does it work?
Lethal factors-What virulence factor is this a component of? How does it work?
What effects will these antigenic factors have on tissues?
- Edema factor:
- One of the antigenic components of the complex toxin.
- Calmodulin dependent adenylate cyclcase increase cAMP causes build up fo fluid in tissue as well as inhibits neutrophils.
- Lethal factor:
- Antigenic component of the complex toxin.
- Lethal toxin is a zinc metalloprotease plus Protective Antigen which acts as a binding domain.
- Lethal factor stimulates macrophages to release IL-1 beta and TNF alpha and cleaves MAP kinase (this is responsible for the inflammatory response, but without cannot kill anthrax)
- Tissue swelling (edema), darkening of the tissue, necrosis.
- When the lethal factor induces the release of the cytokines IL-1 beta and TNF- alpha from the macrophages they induce signs of shock and eventually death.
What is characteristic of anthrax just before death?
A MASSIVE septicemia, bactermia occluding the vasculature, overwhelming the body. Death occurs. Bleeding from orifices. Spread of infection.
How can we diagnose Anthrax?
- Carcasses are bloated & DO NOT EXPERIENCE rigor mortis.
- Bleeding ensues from the mouth, anus, nose.
- Blood is collected from the animal and stained with polychrome methylene blue and will show BLUE BACTERIA WITH PINK CAPSULES… This is called a McFadyeans capsule stain. (unique to anthrax)
What is anthrax characteristic appearance on blood agar?
Medusa head colonies.
What are the 3 forms of anthrax disease in man?
- Cutaneous-endospores enter abraded/ damaged skin
- Pulmonary- woolsorters disease- via inhalation of spores
- Intestinal via ingestion by infected meat, vegetation, or water.
How can we control anthrax?
- Do not open carcass. this will facilitate spore fomration and environmental contamination.
- Annual vaccination.
- Burn infected carcasses AWAY from water sources.
What kind of bacteria is Clostridum?
Discuss any enzymes, toxins, and sensitivities.
- Gram positive large rods
- Resistant spores (similar to bacillus)
- Strict anaerobes (tell me how im sposed to breath with NO AIR)
- Grow VERY rapidly (similar to bacillus)
- Produce VFA
- Contain enzymes including proteases, saccharases.
- Produce 2 toxins:
**1. tetanus toxin on plasmid.
- Botulism toxin on lysogenic phage.**
* Antimicrobial sensitive
Where is Clostridia found? What are the 3 types of Clostridium?
- Found in soil, alimentary tract of animals, and in feces.
1. Neurotoxic clostrida
2. Histotoxic clostridia
3. Enteropathogenic/ enterotoxemia clostridia
Neurotoxic Clostridia:
Most susceptible?
Moderately susceptible?
Comparitively resistant?
Resistant?
- Horses/ Humans.
- Ruminants/ pigs
- Carnivores
- Poultry
