20 Anthrax Flashcards
what causes anthrax
Bacillus anthracis is the etiological agent of the disease known as anthrax
what is anthrax gram
Gram-positive
what is the ‘respiration’ of anthrax
aerobic
what shape is anthrax
rod
does anthrax move
non-motile
do anthrax form spores
key characteristic is that it forms endospores which are oval and located centrally in the cell
where are anthrax spores
spores persist in the environment
what disease is anthrax
anthrax primarily disease of herbivores
what animals is anthrax common in
sheeps, goats, cattle, horse
how do humans get anthrax
Infections result from direct contact with an infected animal or from exposure to spores in animal products. Person-to-person transmission is extremely rare
how do spores enter humans
Spores enter through skin lesions and mucous membranes
what happens when B. anthracis replicates or its spores germinate
Toxins are produced and accumulate
The toxins cause fluid accumulation (swelling, edema) and cell damage
what happens from cutaneous anthrax
Because of fluid accumulation and cell damage a papule starts to develop which will ulcerate and necrotise to form an Escher
what happens if spores are inhaled
pulmonary anthrax
symptoms of pulmonary anthrax
growth and toxin production in lungs causes:
> swelling mediastinal (thoracic cavity) haemorrhage, septicaemia and possibly death
what happens if spores are ingested
intestinal anthrax
symptoms of intestinal anthrax
rapid onset abdominal pain and abdominal swelling due to haemorrhage, septicaemia and death
what may cutaneous anthrax cause when disseminate
10% of cases disease will disseminate and may result in
- Septicaemia (bad)
- Haemorrhagic meningitis (very bad)
- If the colonising bacteria continue to multiply and produce toxins then there is the risk of death (worse than very bad)
how many anthrax toxins are there
three toxin subunits
what are the three toxin subunits
- Protective antigen (PA) 2. Lethal factor (LF)
3. Edema factor (EF)
what is protective antigen
will bind the other two factors
- Which is the receptor binding subunit
what is the lethal factor
(LF)
- Enzyme subunit
what is Edema factor (EF)
subunits can form two active toxins, lethal toxin (LT) (PA + LF) and edema toxin (ET) (PA +EF)
which are the non-toxic subunits
PA, LF and EF are non-toxic alone
where does the protective antigen bind
binds to the host cell membrane and to lethal factor or edema factor
what is endocytosed
lethal toxin or edema toxin complex is endocytosed
what is released from endosome
Inside the cell LF or EF are released from the endosome
what does LF do
LF alters host cell signal pathways to trigger apoptosis
what does EF trigger
EF triggers rapid increase in cAMP levels resulting in edema
the anthrax toxin mode of action
Once in the phagosome – release of toxins into the host cell
B. anthrasis capsule composed of
poly-D-glutamic acid
how is anthrax detected
Swab and Gram stain to reveal - Large Gram-positive bacilli, often in chains
Culturing samples from blood, skin lesions or respiratory secretions on blood agar
what is anthrax like when swabbed
- Non-haemolytic (anthrax is non-haemolytic)
- Characteristic colonies
where do antitoxins bind
bind to protective antigen with high affinity in a dose-dependent manner
how are antitoxins administered
adjunct to intravenous antimicrobials if there is a high level of clinical suspicion for systemic anthrax
what makes B. anthracis a good weapon
Can be easily manufactured using standard laboratory equipment
Persistence of endospore in environment
Delayed onset of recognisable symptoms renders treatment ineffective
Pathogenicity
No obvious colour, taste, or odour
