Bacillus spp

Question 1

characteristics of spores of bacillus spp

Answer 1

• hardy cells that enter a dormant phase
• contain thick DNA
• Thick cell layers to protect them from environmental stress
• Protective structure makes them incredibly resistant to environmental stressors such as heat, acid & alcohol

Question 2

Dormancy and Longevity of bacillus spp

Answer 2

• spores can remain dormant for years
• IN case of Bacillus anthracis, spores can survive for up to 50 years in an unopened carcass

Question 3

Resistance quality of bacillus spp

Answer 3

• highly resistant to adverse conditions like heat & drying
• Different spore forming bacteria may exhibit varying levels of resistance
• Bacillus spores are more resistant to heat compared to Clostridium spores
  • Although many Clostridium spp are resistant to alcohol & heat

Question 4

Morphology of bacillus spores

Answer 4

• spores can appear in various morphologies
  
  • Terminal, subterminal or larger than the cell
• Some spores are located at the ends, in the middle or have internally localised spores
  
  • Some may even look like a dumbbell

Question 5

Survival & regeneration of bacillus spores

Answer 5

ability to form spores means that they can survive in the environment & later regenerate into vegetative cells hat can infect humans or animals

Question 6

Aetiological agent of Anthrax

Answer 6

Bacillus anthracis

Question 7

Spp that is affected by Anthrax

Answer 7

Cattle & sheep
horses
pigs
dogs & cats
humans

Question 8

Plasmid characteristics of bacillus anthracis

Answer 8

• rovides the bacterium with a thick capsule
  
  • Prevents phagocytosis in the host’s immune cells
  • Allows the bacteria to evade the initial immune response & multiply within the host
  • Capsule is not recognised by most hosts, which aids in evading the immune system

Question 9

What does plasmid of bacillus anthracis produce

Answer 9

It produces a potent endotoxin with 3 subunits: protective antigen, lethal factor & oedema factor

Question 10

What can the products of Bacillus anthracis cause

Answer 10

These components work together to cause oedema & severe tissue damage in the host

Question 11

Typical clinical signs of bacillus anthracis

Answer 11

• typically manifests as pre-acute or acute septicaemic disease leading to rapid death in the host
• Sudden death (Animals are often found dead without prior obvious symptoms)

Unclotted blood

• Rapid decomposition of host tissues
• Incomplete rigor mortis
• Rapid bloating & oedema
• Cytopredation

Question 12

Signs of anthracis in cattle & sheep

Answer 12

• most commonly found dead
• Acute cases may show pyrexia (temp. up to 42oC)
  
  • Rapid respiration, abortion , SC oedema, dysentery & blood stained deep yellow milk
• Rapidly affected

Question 13

Post mortem of cattle & sheep with anthracis

Answer 13

rapid bloating, incomplete rigor mortis, oedema, dark unclotted blood

Question 14

Signs of anthracis in horses

Answer 14

• may experience sudden death with swelling of the body & legs or they might linger for a few days with colic & body swelling before dying
• Horses and pigs are generally less affected than ruminants, though cases in pigs have been reported in places like Papua New Guinea

Question 15

Signs of anthracis in pigs

Answer 15

Infection is often localised especially in the throat with fever lasting 2-7 days before death

Question 16

anthracis in Dogs & cats

Answer 16

• highly resistant but should be monitored if exposed to infected carcasses
• are relatively resistant, but exposure should still be carefully monitored

Question 17

anthracis in humans

Answer 17

• can contract severe forms
• can acquire anthrax, particularly if exposed to a high dose, but infections are treatable if identified early

Question 18

Describe cutaneous anthrax in humans

Answer 18

enters through skin abrasions, leading to large sores with necrotic centres

Question 19

describe Pulmonary anthrax (Woolsorter’s disease) in humans

Answer 19

• caused by inhaling aerosols of spores from fleece or hides, affecting the lungs
• much more severe

Question 20

describe Intestinal anthrax in humans

Answer 20

• results from ingesting contaminated meat
• All human forms are potentially deadly

Question 21

Diagnosis of Anthrax

Answer 21

• If suspect anthrax, necropsy must not be performed due to high risk of spore aerolisation & spread
  
  • Extremely dangerous to humans & environment

Question 22

Sample collection for anthrax

Answer 22

• Blood smear or swab
• Samples should be ideally collected from distal parts of the body
  
  • Ear (cutting off an ear at the base & sealing it in a bag)
  • Eye socket or fluid from throat swellings/ LN

Question 23

Microscopic examination of anthrax

Answer 23

• demonstrate encapsulated, spore-forming large rods or fluid smear
• typically using a polychrome methylene blue stain to visualise the thick capsule around the bacterium

Question 24

PCr for bacillus anthracis

Answer 24

• specific PCR tests can be performed on blood smears for confirmation
• generally effective, though samples from animals dead from more than 12 hours might be less ideal due to the spread of gut bacteria

Question 25

On farm Immunochromatographic Test for bacillus anthracis

Answer 25

Blood samples from peripheral blood or aspirates from the jugular vein can also be used with these tests

Question 26

Reporting of anthrax

Answer 26

- any suspected cases of anthrax must be immediately reported to the local Department - Always better to report a false alarm than to allow anthrax death to uninvestigated as it poses significant risks & future stock owners & industry