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Bacillus anthrax ,a potent bioweapon


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Microbiology of anthrax

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Bacillus anthrax ,a potent bioweapon

  1. 1. Sporogenous Bacilli Aerobic Bacilli 1.Bacillus anthracis 2.Bacillus cereus 3. Anthracoid bacilli Anaerobic Clostridia 1. Cl.perfringens 2. Cl. tetani 3. Cl.botulinum
  2. 2. -First pathogenic bacteria to be observed under microscope -First bacilli to be isolated in pure culture -First bacilli in which spores were demonstrated -First bacterium used for preparation of attenuated vaccine -First bacterium to be shown cause of disease -First bacterium that evolved as a potent weapon in bioterrorism
  3. 3. Morphology Cultural characteristics Biochemical reactions Resistance Pathogenicity Lab diagnosis Epidemiology Prophylaxis Treatment BIOTERRORISM
  4. 4. -One of the largest pathogenic bactera;4-8x1-1.5 mm in size -Gram +ve, rod shaped, non-motile and non acid-fast -Bamboo stick appearance of long chains -Polypeptidal capsule -Central or sub terminal oval spores
  5. 5. -Aerobic ,Facultative anaerobic -On NA : Colonies are round, grayish white,irregular,raised with “frosted glass” appearance,2-3 mm in diameter. Medusa head /Barrister's wig appearance of colonies under low magnification -On BA: Non-hemolytic colonies -Gelatin stab culture: “Inverted fir tree" appearance -PLET medium: for selective isolation
  6. 6. -Glucose, Maltose, Sucrose fermented with ACID production -Nitrate reduction test -Gelatin liquefaction test All positive -Catalase test RESISTANCE -Spores survive for many years(dry state & soil) -vegetative cells 60 0C x 30 min. -spores 1000C x 10 min. -4% FD & KMnO4 kills spores Duckering: 2% formaldehyde at 30-40 0C for 20 min. disinfects wool & 0.25% at 60 0C for 6 hrs. for animal hair & bristles. -Moist heat kills :
  7. 7. Virulence factors: 1.Capsular polypeptide – inhibits phagocytosis 2.Anthrax toxin –a complex of 3 fractions: -Edema factor(OF or Factor I) whole complex -Protective antigen factor(PA or Factor II) produces local edema -Lethal factor(LF or Factor III) & generalized shock Edema factor + protective antigen = Edema toxin Lethal factor + protective antigen = Lethal toxin
  8. 8. Clinically three forms of Human anthrax occur 1.Cutaneous anthrax 2.Pulmonary anthrax 3.Intestinal anthrax Broadly can be classified into Non Industrial/Agricultural ( Through infected animals): Cutaneous anthrax Rarely intestinal anthrax Industrial Anthrax ( Through animal products): Mostly through animal products( wools, hair, hides, bones) Likely to develop Cutaneous and pulmonary anthrax
  9. 9. 1.Cutaneous Anthrax(95-99% human anthrax) •Mainly in professionals( Veterinarian, butcher, Zoo keepers, persons handling carcasses/hides/hair, loading skin on bare backs-hide porters disease . • Spores infect skin- a characteristic gelatinous edema & congestion develops at the site (Papule- pustule-black ulcer(eschar) .Later a ring of vesicle containing serous fluid surrounds eschar termed as Malignant pustule. •Face ,neck,arms and back are common sites • 80-90% heal spontaneously ( 2-6wks) • 10-20% progressive disease – develop fatal septicemia, death
  10. 10. Different locations & morphology of lesion in cutaneous anthrax
  11. 11. 2.Pulmonar Anthrax- wool sorter's/Ragpicker’s disease: -Acquired with inhalation of spores(bioterrorism-aerosol) -Requires very high infective dose(10,000 t0 20,000 spores) -Inflammatory reaction occurs in trachea, bronchi with hemorrhagic bronchospasm -Presents initially with non -specific symptoms but later with symptoms of severe respiratory infection & severe respiratory collapse -Hemorrhagic meningitis sometimes occurs as complication -Progress to septicemia very rapidly -Mortality rate is very high
  12. 12. 3.Intestinal Anthrax -Rare in man and is found in primitive communities eating dead carcasses of infected animal -Presents with serious severe enteritis, bloody or hemorrhagic diarrhoea,bloody vomit -Fatality rate is 25-60% depending upon treatment
  13. 13. EPIDEMIOLOGY(INDIA) -Anthrax is enzootic in India -An epizootic of anthrax in sheep active AP,TN borders -Largest live stock population in the world -Pondicherry ( JIPMER) - 30 human cases reported ( Mostly Cutaneous, Septicemic or Meningeal) -Vellore ( CMC)- 49 human cases -Chittor ( Rajasthan)- 30 human cases -Tirupati ( Andhrapradesh)- 25 human cases -Midnapur ( WB)- 22 human cases
  14. 14. LABORATORY DIAGNOSIS A. Hematological investigation-not significant B.Bacteriological investigation: Specimen- swabs, pus, pustules, blood ,sputum, feces etc. 1.Microscopy:Gram staining & spore staining Characteristic Mc’ Fadyean’s reaction Immunofluorescent microscopy
  15. 15. 2.Culture: Suitable culture media for selective isolation 3.Animal inoculation : done in guinea pigs, mice & rabbits. 3.Serology(Ascoli’s thermoprecipitation test) 4.Molecular methods : PCR with specific primers 5.Molecular typing: MLVA & AFLL for epidemiological studies
  16. 16. PROPHYLAXIS Humans protected by preventing disease in animals -Veterinary supervision -Trade restrictions -Proper sterilization & disinfection of animal products -Deep burial or cremation of carcasses  Improved industry standards  Safety practices in laboratories  Post-exposure antibiotic prophylaxis
  17. 17. VACCINATION: -Active immunization with Pasteur’s anthrax vaccine -Salvo immune serum in serious toxic cases -Cell free vaccine in high risk groups -Inactivated /killed vaccine for veterinarians & Agri-workers -Sterne vaccine used effectively in livestock's -Alum precipitated toxoid found safe in professionals  3 doses given intramuscularly TREATMENT Effective antibiotics in humans: Sulphonamides,ciprofloxacin,penicillin,erythromycin, Vancomycin,doxycyline,chloramphenicol FDA -approved ciprofloxacin,doxycycline and penicillin
  18. 18. BIOTERRORISM-anthrax as a bioweapon -Anthrax was used by Scandinavian rebels against Russians -Operation vegetarian by Royal Air Force against Germany in 1944 ,an anti-livestock operation -In 1997-accidental release of anthrax spores from biological weapons complex in Russia infected 94 people ,68 died -In Oct.2001 anthrax attacks in USA termed Amerithrax(FBI) 22 cases- 11 inhalation(5 deaths),11 cutaneous(no deaths)
  19. 19. -Important cause of food poisoning -Distributed widely in nature(soil, vegetables & foods) -Non-Capsulated but Motile (few non-motile strains ) -Two patterns of food borne disease are produced: 1.Diarrhoeal type: -caused by serotypes 2,6,8,9,10 & 12 -associated with wide range of foods -characterized by diarrhea & abdominal pain 2.Emetic type(fried rice syndrome) caused by STs 1,3 & 5 - associated with consumption of cooked rice - characterized by acute nausea & vomiting For isolation MYPA medium is used 10,00000 bacilli/gram of stool is significant
  20. 20. ANTHRACOIS /PSEUDOANTHRAX -Saprophytic ,spore-forming, non-pathogenic species -They are most common laboratory contaminants (e.g. B.subtilis contaminating blood transfusion bottles -They are opportunistic & may cause septicemia