Exam 2: Bacillus Flashcards
What are Bacillus spp.?
Large gram positive, aerobic or facultative anaerobic rods that produce endospores only under aerobic conditions
What are Clostridium spp.?
Obligate anaerobic, large, gram positive rods that form endospores
What can only spores of clostridium survive?
Oxygen
What is the significance of B. anthracis?
Mammalian pathogen
Anthrax
What is the significance of B. cereus?
Food poisoningm, gangreous bovine mastitis, supperative wound infections
Common soil saprophyte and lab contaminant
What is the significance of B. larvae?
In apiculture
Bee foul brood
What is the significance of B. thuringiensis?
Biologic insecticide
Produces insecticidal crystal protein
Exotoxin used in transgenic plants
What is the significance of B. polymyxa?
Produces protein ionophore antibiotic
Polymyxin B.
What is the significance of B. colistinus?
Produces protein ionophore antibiotic
Colistin
What is the most significant pathogen of the genus in vet med?
B. anthracis
What are the susceptible species (from most to least) to B. anthracis?
Cattle Deer Sheep People Goats Horses Swine Dogs Birds and poikilotherms are resistant
What is the septicemic form of B. anthracis usually acquired through?
Inhalation
How quickly can the septicemic form be fatal?
In 4 hours
What form of B. anthracis do humans normally get?
Skin form, but they can also inhale
What is the incubation period in humans before septicemia?
5-7 days
Does human-to-human transmission occur?
Not as far as we know
What form of B. anthracis can swine and strict carnivores acquire?
Oral/pharyngeal form
What is the infections particle of B. anthracis?
Endospore (most resistant form of life)
How can an endospore be killed?
Autoclave (121 degrees C, 15 psi, 15 min)*
Hot air oven
Formalin
Heat-fixed slides
What happens to vegetative cells in unopened carcasses?
They are easily killed and die rapidly as this is an anerobic environment, but their spores will live on at air interfces
What are the endemic areas of B. anthracis in order of most occurring?
Mississippi river delta Texas gulf coast SE South Dakota NE Nebraska Sacramento/San Joaquin Valleys NW territory Great Slave Lake area
What soils can B. anthracis be found in?
Alkaline soil
High N content
Soils rich in Ca and N
How can B. anthracis be spread?
By periodic flooding
What must soil flora lack?
Certain Sterptomyctes spp.
When do spores form?
During dry periods
What contributes to epidemics?
Alternating wet and dry periods
In an outbreak, what are large numbers of B. anthracis shed through?
Animal amplification
What are the 6 primary forms of disease with B. anthracis?
Septicemic Cutaneous form Pharyngeal form Intestinal form Respiratory form Meningitis
Describe the septicemic form of disease
Herbivores: incubation of 3-7 days, fatal after 1-2 hours after first signs
High fever, bleeding, more prolonged in horse than cow
Horse and swine reported to have low number of organisms in circulation during septicemia
Describe the cutaneous form of disease
Intensely dark, relatively painless edematous eschar
Ulcer with necrotic center (malignant carbuncle)
May become septicemic, but heals rapidly with antibiotic therapy
Reported in people, rabbits, swine, and horses
Describe the pharyngeal form of disease
Reported in swine, dogs, and cats
Subacute to chronic carbuncular lesions of jowl and tongue
Swelling of lips, head, and throat
Severe gastroenteritis
Describe the intestinal form of disease
Reported in people, dogs, and cats
B. anthracis grows readily on cut surface of boiled veggies and sporation occurs
Describe the respiratory from of disease
In people, usually becomes septicemic and rapidly fatal
Describe the meningitis form of disease
CNS signs, only recognized in people
Rare
What is the pathogenesis of anthrax?
- Ingestion, inhalation, skin exposure by spore contact
- Poly-D-glutamate capsule
- To be virulent, it requires 2 different plasmids (1 coding for capsule and 1 coding for toxins)
- Sheer numbers of anthrax overwhelm spleen and a single, multicomponent protein exotoxin is produced
Describe Poly-D-glutamate capsule
Antiphagocytic
Antiopsonic
Nonimmunogenic
Nonantigenic
What are the toxin actions from the exotoxin produced?
Damage/kill phagocytes Increase capillary permeability Prevent clotting Block opsonization Capillary thrombosis occurs BP falls Shock and death follow
What is the toxin a product of?
A 110 Mdal plasmid
What is this toxin specifically?
Tripartite subunit toxin (1 unit binds, 2 units are toxic)
What is the structure of the subunit toxin?
A:B structure (B binds and A is active)
Describe the toxin
Edema factor (EF) Protective antigen Lethal factor (LF)
What does edema factor affect?
Na/K pump
What does protective antigen do?
Binds to cell receptor and allows EF and LF to enter
Describe lethal factor
Dominant virulence factor
Cleaves and inactivates MAPKK1 and MAPKK2, which are enzymes in charge of cell growth
Why is it believed that birds are resistant to anthrax?
The toxin is not produced at 42 degrees C
What would you see from an animal that should make you think about anthrax?
Any sudden death with bleeding from all body openings, unclotted dark blood, delayed rigor mortis
Where should the blood sample for anthrax come from?
Jugular veins
Why should you be quick to bring back a sample on anthrax?
If the animal has been dead more than 1 hour, it is less likely to culture
Why should you not open a carcass believed to have anthrax?
Once exposed to air, spores will be released and infect
What stain smears for anthrax?
Wrights, giemsa, methylene blue, or gram stain
What is anthrax like in vivo?
A large blue bacilli, single or short chains, no spores usually
What are B. anthracis antigens demonstrated in extracts from contaminated products by?
Ascoli test
What is the treatment for anthrax?
Penicillin (cidal) or tetracycline (static), which are only effective early before lethal concentration of anthrax accumulates
Penicillin resistant strains are isolated in Mississippi
What is the immunity to anthrax like?
Mainly humoral, antitoxic
Why is the sterne strain used mostly in US?
Has plasmid for toxins, but not for capsule
What is the vaccine available for people?
Alum-precipitate supernatant toxoid
