Bacillus anthracis

1. Bacillus Anthracis
Anthrax

2. Bacillus Anthracis
 From greek word
“anthrakos”
 Large (1 - 1.2µm in
width x 3 - 5µm in
length), gram (+)
 Non motile
 Facultative anaerobe
 Spore forming (oval,
endospores)
 Polypeptide capsule
 Produces 3 exotoxins

3. Endospores
 Can survive in dry soil
for decades
 Sporulation requires
oxygen
 Can be killed by:
 Vegetative cells in 60 0 C X
30 min
 Spores in 100 0 C X 10 min
 4% Formaldehyde
 4% KMnO4
 Hypochlorite ( 0.5%)

4. Natural Infection Sources
 Primarily domesticated and wild animals (sheep,
cows, horses, goats)
 Soil rich in organic matter (pH < 6.0) in regions
where dramatic changes occur in climate
 Streams, insects, wild animals, birds, contaminated
wastes
 Undercooked meat
 Contact with flesh, bones, hides, hair, & excrement
 Cutaneous & inhalational infections are most
common

5. Thos who are at increased risk
 Tanneries
 Textile mills
 Wool sorters
 Bone processors
 Slaughterhouses
 Laboratory workers
 Military

6. Biological Weapon
 Germany (1915)
 Manchuria (1937)
 Swerdlowsk, Russia (1979)
 South Africa (1978-1980)
 Tokyo (1983)
 USA, Washington (2001)

7. Forms of Anthrax
 Cutaneous anthrax
 Skin
 Most common
 Spores enter to skin through small lesions
 Inhalation anthrax
 Spores are inhaled
 Gastrointestinal (GI) anthrax
 Spores are ingested
 Oral-pharyngeal and abdominal

8. Pathogenesis
 The infectious dose of B. anthracis in humans is
unknown (though for primates the LD50 is 8,000-
10,000 )
 Virulence factors are
 Capsule
 3 toxins (Edema factor (EF), Lethal factor (LF) and Protective
antigen (PA))

9. Capsule
 Glycocalyx. Sticky, gelatinous polymer external to cell
wall.
 pX02 plasmid
 Made up of poly-D-glutamic acid
 Non-toxic on its own
 A-B model of toxicity. Two proteins must combine to
create the toxic complex. Protective antigen is the
common protein and both EF and LF need PA to get into
the cell and cause damage.
 Only encapsulated B. anthracis virulent
 Most important role during establishment of disease.
Protects against phagocytosis & lysis during vegetative
state.

10. Toxins
 pX01 plasmid
 PA, EF & LF (50% of proteins in the organism)
 A-B model
 PA+LF  lethal activity
 EF+PA  edema
 EF+LF  inactive
 PA+LF+EF  edema & necrosis; lethal
 Protective antigen (PA, 83kDa)
 Pag gene
 Binds to receptor & helps internalize other 2 proteins
 Edema factor (EF, 89 kDa)
 Cya gene
 Adenylate cyclase
 Affects all cells
 Lethal factor (LF, 87 kDa)
 Lef gene
 Metalloprotease
 Cleaves mitogen activated protein kinase kinsase (MAPKK)
 Affects only macrophages

11. Stages of infection
 Encounter: organism and body surfaces
 Adhesion: generalized and receptor-specific
 Initial multiplication  in situ colonization
 Invasion  breaching of anatomic barriers
 Lymphatic stage  invasion of bloodstream
 Generalized infection, metastases  local
colonizations, “tropisms” of certain organisms

12. Pathogenesis
Abrasion, inhalation,
ingestion
Introduced
Phagocytosed by
Macrophages
Regional LNs
Germinate inside
macrophages
Vegetative Forms
Release
Multiply in lymphatics
Blood stream
10 7 to 10 8/ml
Septicemia
Death

13. Phases of symptoms
1st phase (within 7 days) 2nd phase (within 2-3 days)
 Fever (> 37,7°C/100°F)
 Chills or night sweats
 Headache, cough, chest
discomfort, sore throat
 Joint stiffness, joint
pain, muscle aches
 Shortness of breath
 Enlarged lymph nodes,
nausea, loss of
appetite, abdominal
distress, vomiting,
diarrhea
 Meningitis
 Breathing problems,
pneumonia
 Shock
 Swollen lymph glands
 Profuse sweating
 Cyanosis (skin turns
blue)
 Death

14. Cutaneous Anthrax
 95% human cases are cutaneous infections
 Incubation period 2-3 days
 Small, pruritic, non-painful papule at inoculation
site
 Papule develops into hemorrhagic vesicle (24-48
hrs) & ruptures
 Slow-healing painless ulcer (d=1-3 cm) covered
with black eschar, surrounded by edema
 Infection may spread to lymphatics causing local
adenopathy
 Septicemia may in 20% of cases
 20% mortality in untreated cutaneous anthrax

15. Cutaneous Anthrax

16. Inhalation Anthrax
 Incubation: 1 to 7 days with acute onset (may develop in
a few hours)
 Very high doses of bacteria (bio-weapon aerosoles)
 Initial phase
 Nonspecific (mild fever, malaise)
 Second phase
 Severe respiratory distress
 Fever, dyspnea, cyanosis, rales, tachycardia, feeble pulse,
hypotension, mediastinal widening, eventual death
 Vomiting, sweating, axiety
 Lesions in mediastinal lymph nodes, carried there by
alveolar macrophages, causing edema, toxemia,
bacteremia
 Case fatality: 75 to 90% (death in 2 or 3 days if
untreated)

17. Inhalation Anthrax
Widened
mediastinum
on x-ray

18. GI Anthrax
Oropharyngeal Abdominal (common)
 Caused by deposition
and germination of
spores in the upper
gastrointestinal tract
 Local lymphadenopathy,
edema, sepsis develop
after an oral or
esophageal ulcer
 Caused by deposition
and germination of
spores in the lower
gastrointestinal tract,
which results in a
primary intestinal lesion
 Abdominal pain and
vomiting appear within a
few days after ingestion

19. Incubation: 2 to 5 days
 Severe gastroenteritis common (due to
undercooked & contaminated meat)
 Case fatality rate: 25 to 75%
• Mucosal lesion (lesions are edematous, with
black eschar) to the lymphatic system
 Nausea, anorexia, vomiting, fever
 Progresses to severe abdominal pain and bloody
emesis and diarrhea
 Ascites may develop on day 2 - 4
 Death 2 to 5 days after onset of symptoms
 Rare in developed countries

20. Diagnosis
 Gram stain
 Culture of B. anthracis from the blood, skin lesions,
vesicular fluid, or respiratory secretions
 X-ray and Computed Tomography (CT) scan
 Rapid detection methods
- PCR for detection of nucleic acid
- ELISA assay for antigen detection
- Other immunohistochemical and
immunoflourescence
 Examination

21. Treatment
• Penicillin is drug of choice (ciprofloxacin, erythromycin,
chloramphenicol, doxycycline) 60 days
• Vaccine (for laboratory workers, livestock handlers,
active duty military members) BioThrax/Anthrax
vaccine
• Do not incise lesions
• Eschar is not dangerous after treatment
• The patient must remain hospitalized until fully cured

22. Prevention
 Annual animal vaccination
 Disposal of animal carcasses: disinfect with oil, burn,
bury deep, covered with quicklime.
 Spores will not form inside the carcass, and
putrefaction kills the Bacillus. Flies feeding on
incoagulable blood may be a problem.
 Gloves, masks, disinfection of materials.
 Health edu
 Death, ilness reports

23. Bioterrorism
‘First choice’ weapon
o “Poor Man’s Nuke”
o Availability
o Silent, unnoticeable
o Deniability
o Slow action
o Highly lethal
o Non-contagious
o Prevention (enemy can easily vaccinate themselves
prior)
o UV resistant

24. Category A Biological weapon
High-priority agents include
organisms that pose a risk to
national security because they :
 can be easily
disseminated or
transmitted person-to-
person;
 cause high mortality,
with potential for
major public health
impact;
 might cause public
panic and social
disruption;
and
 require special action
for public health
preparedness
These agents include:
 Bacteria: Bacillus anthracis
(anthrax); Yersinia pestis
(plague); Clostridium botulinum
toxin (botulism); Francisella
tularensis (tularaemia);
 Filoviruses: Ebola
hemorrhagic fever, Marburg
hemorrhagic fever; and
 Arenaviruses: Lassa (Lassa
fever), Junín (Argentine
hemorrhagic fever) and related
viruses