Bacteria 1 (gram +ve): Anthrax

Question 1

Which bacterium causes anthrax?

Answer 1

Bacillus anthracis, gram+ rod spore forming

• zoonotic disease
• potential biological warfare disease
• Spores are highly resistant - these (endo)spores are produced due to lack of nutrients -> do not multiply or have metabolic activity
• Frequently appears in chains of cells
• commonly found in soil of grazing areas

Question 2

How is the disease passed on to humans?

Answer 2

Question 3

What is the pathophysiology of anthrax?

Answer 3

• Bacteria taken up in macrophage
• Migrate to regional lymph node -> regional haemorrhagic lymphadenitis

(cutaneous anthrax does not commonly goe into blood stream; inhalational anthrax: perihilar LNs)

• The endospores germinate within macrophages
• The bacteria are released from the macropahges and continue to multiply in the lymphatic system
• Then released into bloodstream and cause massive speticaemia
• No evidence of immune response against the bacilli
• GI anthrax pathophysiology not clear
• three toxins produced that cause death:

Question 4

What are the clinical symptoms of anthrax infection?

Answer 4

• inhalational anthrax has 80 - 100% fatality rate
• you need a high index of suspicion to diagnose anthrax (e.g. bioterrorism, endemic area, postal workers)

Question 5

How do we treat anthrax?

Answer 5

Consensus recommendations call for ciprofloxacin or doxycycline until penicillin sensitivity is proven., Post exposure prophylaxis should be considered following a possible deliberate aerosol release

Question 6

Where is the disease mostly prevalent?

Answer 6

Africa and then also middle east

Question 7

Which clinical sign is typical for cutaneous anthrax?

Answer 7

black eschar

• generally single lesion
• mortality less than 5%
• incubation period 2 - 7 days

small pimple -> central vescile

• > black central eschar with fever, malaise, headache
• > day 10 eschar begins to resolve

Question 8

How do you get GI anthrax and how does it present?

Answer 8

• similarly trasmitted form: oropharyngeal anthrax

Question 9

How does inhalational anthrax present on a CXR?

Answer 9

Mediastinal widening

Question 10

How do we diagnose anthrax?

Answer 10

Gram stain shows chains, methylene blue staining shows chains of capsules

Culture in blood agar

Anthraxin skin test (rapid diagnostic confirmation)

other tests:

• ELISA
• Fluorescent antibody staining
• PCR

Question 11

How do we prevent anthrax?

Answer 11

• limit exposure to anthrax spores
• control of occupational exposure -> disinfection

Vaccination of live stock and high risk workers

Question 12

What?!?! Anthrax vaccine? Which ones exist?

Answer 12

Question 13

how would you control an outbreak?

Answer 13

Question 14

MCQ key points

Answer 14

• Anthrax lends itself well to a picture based diagnosis. • One of the distinguishing features of anthrax eschar and e.g. Rickettsia/tick eschar is that the anthrax lesion will have significant surrounding oedema.
• Remember the different manifestations of anthrax for your differentials – GI/respiratory infection will not have the diagnostic eschar of cutaneous anthrax.

Inhalational anthrax is initially a clinical diagnosis requiring a high index of suspicion. , Clinical laboratory features may include an elevated leukocyte count, neutrophilia, elevated transaminases, metabolic acidosis and elevated creatinine., The gold standard and most sensitive test is still classical microbiological culture of the organism from skin lesion aspirate, blood, pleural fluid or cerebrospinal fluid.