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Medical Microbiology lectures > L.3 GPB Bacillus Anthracis > Flashcards

L.3 GPB Bacillus Anthracis Flashcards

1
Q

What is the classification of B.anthracis?

A

GPB

GPB stands for Gram Positive Bacilli.

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2
Q

What are the characteristics of B.anthracis?

A

Non-motile, endospore forming, facultative anaerobe.

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3
Q

What disease is caused by B.anthracis?

A

Anthrax.

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4
Q

What are the forms of anthrax disease?

A
  • Cutaneous
  • GI tract
  • Respiratory
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5
Q

In which regions is anthrax most common?

A
  • Central and South America
  • Sub-Saharan Africa
  • Central and southwestern Asia
  • Southern and eastern Europe
  • Caribbean
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6
Q

What percentage of human anthrax cases worldwide is cutaneous anthrax?

A

95-99%.

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7
Q

What is the mortality rate for anthrax?

A

<1-20%.

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8
Q

How many cases of anthrax occur per year in the USA?

A

1-2 cases.

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9
Q

What is the reservoir for B.anthracis?

A

Dormant spores in the environment, e.g., soil.

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10
Q

Why is B.anthracis difficult to eradicate from endemic areas?

A

Due to the presence of endospores.

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11
Q

What type of infection is anthrax considered?

A

Zoonotic infection.

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12
Q

What are the modes of entry for B.anthracis?

A
  • Ingestion
  • Inhalation
  • Penetration of spores through skin
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13
Q

What is the most common form of anthrax disease?

A

Cutaneous anthrax.

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14
Q

How do endospores lead to cutaneous anthrax?

A

Endospores come in contact with open breaks in human skin.

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15
Q

What occurs when spores germinate locally in cutaneous anthrax?

A

Vegetative cells create papule which extend to large fluid-filled sacks.

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16
Q

What happens upon rupturing of the fluid-filled sacks in cutaneous anthrax?

A

Tissue necrosis occurs.

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17
Q

What is the characteristic lesion associated with cutaneous anthrax?

A

Black lesion called ‘eschar’.

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18
Q

What complications may arise from cutaneous anthrax?

A
  • Cellulitis
  • Meningitis
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19
Q

What is the fatality rate for untreated cases of cutaneous anthrax?

A

20%.

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20
Q

What happens to the mortality rate of cutaneous anthrax with treatment?

A

Mortality rate drops to zero.

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21
Q

What is the primary cause of gastrointestinal anthrax?

A

Ingestion of undercooked meat infected with spores

Gastrointestinal anthrax progresses from the mouth to the rectum, forming from papule to eschar.

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22
Q

List the symptoms of gastrointestinal anthrax.

A
  • Abdominal Pain
  • Nausea
  • Vomiting of blood
  • Bloody diarrhoea

These symptoms arise due to the infection process and tissue damage.

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23
Q

How is respiratory anthrax contracted?

A

Inhalation of spores

Inhaled spores lead to severe respiratory symptoms and complications.

24
Q

What are the symptoms of respiratory anthrax?

A
  • Coughing up blood
  • High fever
  • Tachycardia
  • High blood pressure

These symptoms indicate severe systemic infection and can lead to rapid deterioration.

25
What are the sequelae of respiratory anthrax?
* Haemorrhage * Mediastinal lymph node necrosis * Bacteraemia ## Footnote These complications are associated with the spread of the infection and high mortality.
26
Which type of anthrax has the highest mortality rate?
Respiratory anthrax ## Footnote This form is particularly lethal due to rapid progression and severe symptoms.
27
Define bioterrorism.
The intentional release of viruses, bacteria, or other germs that can sicken or kill people, livestock, or crops ## Footnote This definition is provided by the CDC.
28
Why is anthrax considered a good weapon for bioterrorism?
Can be released quietly and without anyone knowing ## Footnote Anthrax has been used as a bioterrorism weapon for over 100 years.
29
What major bioterrorism event occurred in 2001?
2001 US postal system attacks resulting in 22 deaths ## Footnote This incident highlighted the dangers of anthrax as a bioweapon.
30
Describe the entry mechanism of Bacillus anthracis.
Ingestion, inhalation, or penetration of spores via skin, GI-tract, or lungs ## Footnote These routes facilitate the initial infection process.
31
What happens during the colonization phase of Bacillus anthracis pathogenesis?
Spores are phagocytosed by macrophages and germinate inside, leading to release of active bacterium via cytolysis ## Footnote This process allows the bacteria to evade the immune response initially.
32
How does Bacillus anthracis evade the immune system?
* Poly D glutamic acid capsule (antiphagocytic) * Protective antigen (facilitates toxin entry) ## Footnote These factors help the bacteria survive and cause disease.
33
What are the two main factors that cause host damage in Bacillus anthracis infection?
* Oedema factor (causes fluid buildup + swelling) * Lethal factor (kills immune cells + disrupts cell signalling) ## Footnote These factors contribute to the severity of the disease.
34
What occurs during the spread phase of Bacillus anthracis infection?
Spores form again and contaminate the environment ## Footnote This allows for further transmission and potential outbreaks.
35
What is the function of the capsule in virulence factors?
Prevents subsequent ingestion by macrophage and aids survival until enough toxin is produced to cause disease ## Footnote Essential for full anthrax disease
36
What is the role of protective antigen in anthrax?
Secreted by active bacteria and binds to immune cells via cell surface protein ANTxr1 ## Footnote Forms a channel in the cell membrane
37
What are the two plasmid-encoded exotoxins associated with anthrax?
* Lethal factor * Oedema factor
38
What type of enzyme is the lethal factor?
Zinc metalloprotease ## Footnote Cleaves MAPK1 and 2, preventing cells from making energy
39
What is the consequence of the lethal factor's action on cells?
Cells die by apoptosis as a result of energy deprivation
40
What is the function of the oedema factor?
ADP ribosyl transferase that converts ATP to cAMP ## Footnote Activates Kinase A, which is responsible for regulating multiple signaling pathways
41
What inappropriate immune response does the oedema factor cause?
Causes necrosis and bleeding
42
What are the potential consequences of the immune response triggered by anthrax toxins?
Multi-organ failure, septic shock, and death
43
What are AB toxins?
Activity binding toxins ## Footnote They consist of two components: an active enzyme and a binding component
44
What is Bacillus anthracis classified as in terms of hazard?
Hazard Group 3 organism ## Footnote All suspected cases should be worked up in Category 3 Lab Facility.
45
What types of specimens are collected for B. anthracis investigation?
* Cutaneous (95%) = Tissue, Vesicle or eschar lesion Swabs * Gastrointestinal (5%) = Faeces * Inhalation (<1%) = CSF, Blood, Tissue Samples, Lung aspirates, Pleural fluid
46
What agar media are used for culturing B. anthracis?
* Blood agar * PLET agar
47
At what temperature and duration should B. anthracis cultures be incubated?
37C for 24-48hrs
48
What are the colonial morphology characteristics of B. anthracis on Blood agar?
Non-haemolytic, grey/white flat colonies, 2-5mms, tacky on loop
49
What are the colonial morphology characteristics of B. anthracis on PLET agar?
Cream/pale teal in colour, thick cream rim, mucoid, large colonies
50
What are the basic characteristics of Bacillus anthracis?
* Gram positive bacilli (large box car ends with central spores) * KOH negative * Catalase positive * Oxidase negative * Non-motile
51
What confirmatory tests can be used for B. anthracis?
* MALDI-TOF * VITEK
52
What molecular detection method is used for B. anthracis?
RT-PCR of pag gene, cya gene, Lef gene
53
What is the treatment for cutaneous B. anthracis infection?
Ciprofloxacin
54
What is the treatment regimen for inhalation B. anthracis infection?
* Ciprofloxacin * Rifampicin * Vancomycin
55
What preventive measure is recommended for workers at high risk of exposure to B. anthracis?
Vaccination

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