Gram Pos: Bacillus

Question 1

Describe the key bacterial characteristics of Bacillus.

Answer 1

-gram pos rod in chains
-aerobes or facultative anaerobes
-endospore forming (most durable cell type) *
-catalase + & oxidase -
-motile except B. Anthracis (non motile) *
-Medusa head colonies
-ubiquitous in soil (soil saprophytes) *
-majority non path environmental organisms
-most IMP pathogen (B. Anthracis) = obligate mammalian pathogen *
-sporadic cases in livestock
-REPORTABLE

Question 2

Describe endospores.

Answer 2

-cryptobiotic state of dormancy for long periods
-resistant to adverse conditions
-one endospore formed per vegetative cell as response to nutrient depletion
-forms intracellularly & released as free spores when exposed to O2
-Koch described spore formation in B. Anthracis & used the bacteria in an experiment leading to Koch postulates

Question 3

Describe virulence factors & pathogenesis of B. Anthracis.

Answer 3

-sus of animals for replication
-survival of endospore in soil = exposure of carcass to O2
-ecological cycle of infection (seasonal disease)

Question 4

Describe the predisposing factors of B. Anthracis.

Answer 4

inc exposure of animals to anthrax spores in soil
-history of previous anthrax death & buried carcass
-soil conditions: alkalinity, high in Ca & N, high moisture
-warm temp
-cycles of flooding & evaporation
>soil rearrangement
>endospore conc inc in standing surface water
-drought
>animals forage closer to ground -> soil ingestion & mechanical injuries

Question 5

Describe the modes of infection of B. Anthracis.

Answer 5

1. Cutaneous
2. GI (ingestion) ***
3. Inhalation

Question 6

Describe the B. Anthracis capsule contents.

Answer 6

-polymer of D-glutamic acid
-encoded on plasmid pXO2
-only made in vivo
-anti-phagocytotic
virulence depends on presence of BOTH capsule & tripartite anthrax toxin

Question 7

Describe the anthrax toxin - tripartite lethal combination.

Answer 7

3 sep proteins encoded on plasmid pXO1
1. Protective antigen (PA): cell binding factor for translocation into cell
2. Edema factor (EF): calmodulin dependent adenylate cyclase
-enters cell following binding to PA
-inc levels of cAMP -> disturb water homeostasis -> edema
-neutrophils targeted
3. Lethal factor (LF): zinc metalloprotease
-cell death & hypoxia induced tissue injury & shock -> necrosis & hemorrhage

Question 8

Describe the species of vet IMP.

Answer 8

-incubation period from hrs to days
-CS varies w species, dose, route of inf

Question 9

Describe peracute septicemia in ruminants.

Answer 9

-rapidly fatal w respiratory distress & shock
-bleeding from orifices *
-PM: dark unclotted blood, incomplete rigor mortis (bc inc cAMP)
-splenomegaly *

Question 10

Describe the direct examination of samples.

Answer 10

-collect peripheral blood from tail vein
-blood & organ smear stained w polychromatic methylene blue (McFadyean) -> blue stain organisms w a pink capsule
-gram stain: chains of encapsulated gram + non spore forming rods, non motile, rectangular w square ends
-aerobic culture on blood agar
-PCR for detection of B. Anthracis DNA
*BSL3 agent, ID in labs only

Question 11

Describe B. Anthracis treatment & control.

Answer 11

1. Endemic
   -annual vaccines
   -LA pen during outbreaks
2. Non endemic
   -quarantine herd
   -PPE
   -treat all animals w LA antimicrobials
   -observation of animals for 2wks
   -vaccinate 8-12d after antibiotic treatment
   -incinerate carcass or deep burial (>6.5ft) under layer of quicklime (anhydrous Ca oxide) *
   -disinfect

Question 12

Describe the zoonosis in anthrax.

Answer 12

‘Woolsorters disease’
-ingestion rare
-cutaneous most common
-pulmonary
-injection
*bioterrorism