3. History Caused by Bacillus anthracis Human zoonotic disease
Spores found in soil worldwide
Primarily disease of herbivorous animals
Sheep, goats, cattle
Many large documented epizootics
Occasional human disease
Epidemics have occurred but uncommon
Rare in developed world

4. Epidemiology Three forms of natural disease Inhalational Cutaneous
Rare (<5%)
Most likely encountered in bioterrorism event
Cutaneous
Most common (95%)
Direct contact of spores on skin
Gastrointestinal
Rare (<5%), never reported in U.S.
Ingestion

5. All ages and genders affected Occurs worldwide
Endemic areas - Africa, Asia
True incidence not known
World 20, ,000 in 1958
U.S. 235 total reported cases
18 cases inhalational since 1900, last one 1976
Until 2001, last previous case cutaneous 1992

6. Mortality Inhalational 86-100% (despite treatment)
Era of crude intensive supportive care
Cutaneous <5% (treated) – 20% (untreated)
GI approaches 100%

7. Incubation Period Time from exposure to symptoms
Very variable for inhalational
2-43 days reported
Theoretically may be up to 100 days
Delayed germination of spores

8. Human cases – historical risk factors
Agricultural
Exposure to livestock
Occupational
Exposure to wool and hides
Woolsorter’s disease = inhalational anthrax
Rarely laboratory-acquired

10. Transmission No human-to-human Naturally occurring cases Bioterrorism
Skin exposure
Ingestion
Airborne
Bioterrorism
Aerosol (likely)
Small volume powder (possible)
Foodborne (unlikely)

11. Transmission Cutaneous Handling hides/skins of infected animals
Bites from arthropods (very rare)
Handling powdered form in letters, etc.
Intentional aerosol release
May see some cutaneous if large-scale

12. Microbiology Bacillus anthracis Aerobic, Gram positive rod
Long (1-10μm), thin ( μm)
Forms inert spores when exposed to O2
Infectious form, hardy
Approx 1μm in size
Vegetative bacillus state in vivo
Result of spore germination
Non-infectious, fragile

13. Classification
Same family: B. cereus, B. thuringiensis
Differentiation from other Bacillus species
Non-motile
Non β-hemolytic on blood agar
Does not ferment salicin
Note: Gram positive rods are usually labeled as “contaminants” by micro labs

14. Environmental Survival
Spores are hardy
Resistant to drying, boiling <10 minutes
Survive for years in soil
Still viable for decades in perma-frost
Favorable soil factors for spore viability
High moisture
Organic content
Alkaline pH
High calcium concentration

15. Transmission Inhalational Handling hides/skins of infected animals
Microbiology laboratory
Intentional aerosol release
Small volume powdered form
In letters, packages, etc
Questionable risk, probably small

16. Transmission Gastrointestinal Ingestion of meat from infected animal
Ingestion of intentionally contaminated food
Not likely in large scale
Spores not as viable in large volumes of water
Ingestion from powder-contaminated hands
Inhalational of spores on particles >5 m
Land in oropharynx

17. Virulence Factors All necessary for full virulence Two plasmids
Capsule (plasmid pXO2)
Antiphagocytic
3 Exotoxin components (plasmid pXO1)
Protective Antigen
Edema Factor
Lethal Factor

18. Protective Antigen Edema Factor Lethal Factor
Binds Edema Factor to form Edema Toxin
Facilitates entry of Edema Toxin into cells
Edema Factor
Massive edema by increasing intracellular cAMP
Also inhibits neutrophil function
Lethal Factor
Stimulates macrophage release of TNF-α, IL-1β
Initiates cascade of events leading to sepsis

19. Pathogenesis Disease requires entry of spores into body
Exposure does not always cause disease
Inoculation dose
Route of entry
Host immune status
May depend on pathogen strain characteristics

20. Forms of natural disease
Inhalational
Cutaneous
Gastrointestinal
Determined by route of entry
Disease occurs wherever spores germinate

21. Pathogenesis. Inhalational Spores on particles 1-5 m
Inhaled and deposited into alveoli
Estimated LD50 = 2500 – 55,000 spores
Dose required for lethal infection in 50% exposed
Contained in imperceptibly small volume

22. Inhalational Phagocytosed by alveolar macrophages
Migration to mediastinal/hilar lymph nodes
Germination into vegetative bacilli
Triggered by nutrient-rich environment
May be delayed up to 60 days
Factors not completely understood
Dose, host factors likely play a role
Antibiotic exposure may contribute
Delayed germination after antibiotic suppression

24. Vegetative bacillus is the virulent phase
Active toxin production
Hemorrhagic necrotizing mediastinitis
Hallmark of inhalational anthrax
Manifests as widened mediastinum on CXR
Does NOT cause pneumonia
Followed by high-grade bacteremia
Seeding of multiple organs, including meninges

25. Toxin production Has usually begun by time of early symptoms
Stimulates cascade of inflammatory mediators
Sepsis
Multiorgan failure
DIC
Eventual cause of death
Symptoms mark critical mass of bacterial burden
Usually irreversible by this time
Clearance of bacteria unhelpful as toxin-mediated

26. Pathogenesis of cutaneous form.
Spores in contact with skin
Entry through visible cuts or microtrauma
Germination in skin
Disease begins following germination
Toxin production
Local edema, erythema, necrosis, lymphocytic infiltrate
No abscess or suppurative lesions
Eventual eschar formation

28. . In cutaneous anthrax, a malignant pustule develops at the infection site. This pustule is a central area of coagulation necrosis (ulcer) surrounded by a rim of vesicles filled with bloody or clear fluid. A black eschar forms at the ulcer site. Extensive edema surrounds the lesion.

29. The organisms multiply locally and may spread to the bloodstream or other organs (eg, spleen) via the efferent lymphatics. B anthracis remains in the capillaries of invaded organs, and the local and fatal effects of the infection are due, in large part, to the toxins elaborated by B anthracis.

30. Dissemination from the liver, spleen, and kidneys back into the bloodstream may result in bacteremia. Secondary hemorrhagic intestinal foci of anthrax result from B anthracis bacteremia.

31. Cutaneous Systemic disease Can occur, especially if untreated
Spores/bacteria carried to regional lymph nodes
Lymphangitis/lymphadenitis
Same syndrome as inhalational
Sepsis, multiorgan failure

32. Pathogenisis GI form Gastrointestinal Spores contact mucosa
Oropharynx
Ingestion
Aerosolized particles >5 m
Intestinal mucosa – terminal ileum, cecum
Larger number of spores required for disease
Incubation period 2-5 days

33. Gastrointestinal Spores migrate to lymphatics
Submucosal, mucosal lymphatic tissue
Mesenteric nodes
Germination to vegetative bacilli
Toxin production
Massive mucosal edema
Mucosal ulcers, necrosis
Death from perforation or systemic disease

34. Oropharyngeal anthrax
Oropharyngeal anthrax is a variant of intestinal anthrax and occurs in the oropharynx after ingestion of meat products contaminated by anthrax. Oropharyngeal anthrax is characterized by throat pain and difficulty in swallowing. The lesion at the site of entry into the oropharynx resembles the cutaneous ulcer.

35. Clinical Features Symptoms depend on form of disease Inhalational
Cutaneous
Gastrointestinal

36. Inhalational Asymptomatic incubation period Prodromal phase
Duration 2-43 days, ~10 days in Sverdlovsk
Prodromal phase
Correlates with germination, toxin production
Nonspecific flu-like symptoms
Fever, malaise, myalgias
Dyspnea, nonproductive cough, mild chest discomfort
Duration several hours to ~3 days
Can have transient resolution before next phase

37. Fulminant Phase
Correlates with high-grade bacteremia/toxemia
Critically Ill
Fever, diaphoresis
Respiratory distress/failure, cyanosis
Septic shock, multiorgan failure, DIC
50% develop hemorrhagic meningitis
Headache, meningismus, delirium, coma
May be most prominent finding
Usually progresses to death in <36 hrs
Mean time from symptom onset to death ~3 days

38. Laboratory Findings Gram positive bacilli in direct blood smear
Electrolyte imbalances common
Radiographic Findings
Widened mediastinum
Minimal or no infiltrates
Can appear during prodrome phase

39. Cutaneous Most common areas of exposure Hands/arms Neck/head
Incubation period
3-5 days typical
12 days maximum

40. Cutaneous – progression of painless lesions
Papule – pruritic
Vesicle/bulla
Ulcer – contains organisms, sig. edema
Eschar – black, rarely scars

41. Systemic disease may develop
Lymphangitis and lymphadenopathy
If untreated, can progress to sepsis, death

42. Gastrointestinal Oropharyngeal Oral or esophageal ulcer
Regional lymphadenopathy
Edema, ascites
Sepsis
Abdominal
Early symptoms - nausea, vomiting, malaise
Late - hematochezia, acute abdomen, ascites

43. Diagnosis. Early diagnosis is difficult Non specific symptoms
Initially mild
No readily available rapid specific tests

44. Presumptive diagnosis
History of possible exposure
Typical signs & symptoms
Rapidly progressing nonspecific illness
Widened mediastinum on CXR
Large Gram+ bacilli from specimens
Can be seen on Gram stain if hi-grade bacteremia
Appropriate colonial morphology
Necrotizing mediastinitis, meningitis at autopsy

45. Definitive diagnosis
Direct culture on standard blood agar
Gold standard, widely available
Alert lab to work up Gram + bacilli if found
6-24 hours to grow
Sensitivity depends on severity, prior antibiotic
Blood, fluid from skin lesions, pleural fluid, CSF, ascites
Sputum unlikely to be helpful (not a pneumonia)
Very high specificity if non-motile, non-hemolytic
Requires biochemical tests for >99% confirmation
Available at Reference laboratories

46. Other diagnostic tests
Anthraxin skin test
Chemical extract of nonpathogenic B. anthracis
Subdermal injection
82% sensitivity for cases within 3 days symptoms
99% sensitivity 4 weeks after symptom onset

47. Testing for exposure
Nasal swabs
Can detect spores prior to illness
Currently used only as epidemiologic tool
Decision based on exposure risk
May be useful for antibiotic sensitivity in exposed
Culture on standard media
Swabs of nares and facial skin
Serologies
May be useful from epidemiologic standpoint
Investigational – only available at CDC

48. Differential diagnostics
Inhalational
Expect if anthrax
Influenza
Pneumonia
Community-acquired
Atypical
Pneumonic tularemia
Pneumonic plague
Mediastinitis
Bacterial meningitis
Thoracic aortic aneurysm
Flu rapid diagnostic –
More severe in young pts
No infiltrate
No prior surgery
Bloody CSF with GPBs
Fever

49. Cutaneous Expect if anthrax fever no response to 3º cephs
Spider bite
Ecthyma gangrenosum
Pyoderma gangrenosum
Ulceroglandular tularemia
Mycobacterial ulcer
Cellulitis
Expect if anthrax
fever
no response to 3º cephs
painless, black eschar
+/- lymphadenopathy
usually sig. local edema

50. Gastrointestinal Expect if anthrax Gastroenteritis Typhoid Peritonitis
Perforated ulcer
Bowel obstruction
Expect if anthrax
Critically ill
Acute abdomen
Bloody diarrhea
Fever

51. Treatment. Hospitalization IV antibiotics Intensive supportive care
Empiric until sensitivities are known
Intensive supportive care
Electrolyte and acid-base imbalances
Mechanical ventilation
Hemodynamic support

52. Antibiotic selection
Naturally occurring strains
Rare penicillin resistance, but inducible β-lactamase
Penicillins, aminoglycosides, tetracyclines, erythromycin, chloramphenicol have been effective
Ciprofloxacin very effective in vitro, animal studies
Other fluoroquinolones probably effective
Engineered strains
Known penicillin, tetracycline resistance
Highly resistant strains = mortality of untreated

53. Empiric Therapy Until susceptibility patterns known Adults
Ciprofloxacin 400 mg IV q12° OR
Doxycycline 100mg IV q12°
AND (for inhalational)
One or two other antibiotics

54. Pregnant women
Same as other adults
Weigh small risks (fetal arthropathy) vs benefit
Immunosuppressed
same as other adults

55. Susceptibility testing should be done
Narrow antibiotic if possible
Must be cautious
Multiple strains with engineered resistance to different antibiotics may be coinfecting
Watch for clinical response after switching antibiotic

56. Antibiotic therapy Duration Switch to oral 60 days
Risk of delayed spore germination
Vaccine availability
Could reduce to days therapy
Stop antibiotics after 3rd vaccine dose
Switch to oral
Clinical improvement
Patient able to tolerate oral medications

57. Other therapies Passive immunization Antitoxin
Anthrax immunoglobulin from horse serum
Risk of serum sickness
Antitoxin
Mutated Protective Antigen
Blocks cell entry of toxin
Still immunogenic, could be an alternative vaccine
Animal models promising

58. Postexposure Prophylaxis
Who should receive PEP?
Anyone exposed to anthrax
Not for contacts of cases, unless also exposed
Empiric antibiotic therapy
Vaccination

59. Avoid unnecessary antibiotic usage
Potential shortages of those who need them
Potential adverse effects
Hypersensitivity
Neurological side effects, especially elderly
Bone/cartilage disease in children
Oral contraceptive failure
Future antibiotic resistance
Individual’s own flora
Community resistance patterns

60. Post exposure prophylaxis.
Antibiotic therapy
Treat ASAP
Prompt therapy can improve survival
Continue for 60 days
30-45 days if vaccine administered

61. Antibiotic therapy Same regimen as active treatment
Substituting oral equivalent for IV
Ciprofloxacin 500 mg po bid empirically
Alternatives
Doxycycline 100 mg po bid
Amoxicillin 500 mg po tid

62. Prevention. Vaccine Anthrax Vaccine Adsorpbed (AVA) Supply
Limited, controlled by CDC
Production problems
Single producer – Bioport, Michigan
Failed FDA standards
None produced since 1998

63. Vaccine
Inactivated, cell-free filtrate
Adsorbed onto Al(OH)3
Protective Antigen
Immunogenic component
Necessary but not sufficient

64. Vaccine
Administration
Dose schedule
0, 2 & 4 wks; 6, 12 & 18 months initial series
Annual booster
0.5 ml SQ

65. Vaccine
Adverse Effects
>1.6 million doses given to military by 4/2000
No deaths
<10% moderate/severe local reactions
Erythema, edema
<1% systemic reactions
Fever, malaise

66. Infection control. No person to person transmission
Standard Precautions
Laboratory safety
Biosafety Level (BSL) 2 Precautions

67. Decontamination. Skin, clothing Instruments for invasive procedures
Thorough washing with soap and water
Avoid bleach on skin
Instruments for invasive procedures
Sterilize, e.g. 5% hypochlorite solution
Sporicidal agents
Sodium or calcium hypochlorite (bleach)