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Bacillus anthracis. Amanda Russell Anna Bossert. Taxonomy. Kingdom: Bacteria Phylum: Firmicutes Class: Bacilli Order: Bacillales Family: Bacillaceae Genus: Bacillus Species: anthracis. Basic Facts.

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bacillus anthracis

Bacillus anthracis

Amanda Russell

Anna Bossert

taxonomy
Taxonomy
  • Kingdom: Bacteria
  • Phylum: Firmicutes
  • Class: Bacilli
  • Order: Bacillales
  • Family: Bacillaceae
  • Genus: Bacillus
  • Species: anthracis
basic facts
Basic Facts
  • Zoonotic Disease: usually carried by animals, can be transmitted to human hosts under natural conditions
  • Rod-shaped
  • monomorphic
  • Endospore-forming, remain viable in soil and animal products for decades
  • Gram-positive
  • Aerobic respiration
  • Exotoxin producing
  • Grows best at 24-40⁰C
  • Incubation period: 1 to 15 days
  • Three forms: inhaltion, gastrointestinal, cutaneous
virulence factors
Virulence Factors
  • Encoded on two plasmids
    • One encodes for the synthesis of a polyglutamyl capsule (inhibits phagocytosis by macrophages)
    • Other bears genes encoding for the synthesis of exotoxins
  • Exotoxins: three proteins
    • Protective antigen
    • Edema Factor: adenylate cyclase activity, increases cAMP, leads to cytoplasm loss after forming an edema
    • Lethal Factor: interferes with transcription factor in genome (NfkB) which regulates immunity genes. Once these are no longer transcribed, immune response of macrophages will fade.
general mode of infection
General Mode of Infection
  • B. anthracisspores enter the body (lungs, skin lesion, gastrointestinal) and germinate, giving rise to the vegetative form
  • The bacterium begins to produce capsules containing exotoxins, which will help evade the host’s immune system
  • The PA portion will bind to receptors on the membrane of macrophages, when seven complexes are combined they form a ring. This ring will pierce through the membrane and the macrophage will shuttle in the complex as an endosome
general mode of infection cont
General Mode of Infection cont.
  • The PA molecules will form a pore that pierces the endosome membrane, releasing the EF and LF into the cytoplasm of the macrophage
  • EF and LF essentially kill the macrophage, and release the contents of the macrophage to the outside.
  • The endosome enzymes that were released will degrade surrounding tissues, resulting in the common symptoms of anthrax.
cutaneous anthrax
Cutaneous Anthrax
  • B. anthracis comes into contact with a skin lesion, or cut.
  • The spores germinate, producing bacteria, which produce exotoxins to evade the macrophages
  • Infection is manifested in a painless ulcer with a necrotic (dead) center
  • Transmission: coming in contact with infected animals or their products through a skin lesion
symptoms of cutaneous anthrax
Symptoms of cutaneous anthrax
  • Boil-like skin lesion forming a painless ulcer
  • Swelling of the lymph glands
  • Fever
  • Headache
inhalation anthrax
Inhalation Anthrax
  • The spores are inhaled and lodge in the alveolar spaces
  • Alveolar macrophages engulf the spores.
  • Spores germinate within macrophages after failed phagocytosis
  • Bacteria proceed to lymph nodes and spread into bloodstream, where they begin to release the exotoxins
  • Transmission: inhaling the spores of B. anthracis
symptoms of inhalation anthrax
Symptoms of Inhalation Anthrax
  • Initial symptoms: sore throat, mild fever, muscle aches
  • Severe difficulty breathing
  • Septic shock
  • Development of meningitis
  • Respiratory failure resulting in death
gastrointestinal anthrax
Gastrointestinal Anthrax
  • Spores are consumed after eating undercooked meat
  • Spores can evade stomach acid due to their capsule
  • Once in the digestive tract, they begin to germinate and produce bacteria, which release exotoxins
  • After the macrophages have been lysed, the endosome enzymes begin degrading intestinal walls, allowing the bacteria to spread directly into the bloodstream
  • Transmission: Digesting undercooked meat containing spores
symptoms of gastrointestinal anthrax
Symptoms of Gastrointestinal anthrax
  • Serious gastrointestinal difficulty
  • Nausea
  • Fever
  • Abdominal pain
  • Vomiting of blood
  • Severe bloody diarrhea
  • Acute inflammation of intestinal tract
  • Loss of appetite
diagnosis
Diagnosis
  • A diagnosis can be made by taking a smear of a skin lesion (if cutaneous anthrax) and gram-staining the sample.
  • Blood tests that show encapsulated, broad, gram-positive bacilli
  • Cultures: large, flat, nonhemolytic colonies, non-motile, will test positive for catalse, positive for capsule production
  • Confirmatory Diagnosis: Serological tests for toxins at reference laboratories
transmission
Transmission
  • Bacillus anthracis is transmitted mainly through the contact of infected animals or their products, and humans, resulting in cutaneous anthrax
  • It cannot be spread from human to human.
  • 2001: Anthrax was sent in the form of a powder in letters, when the recipient of the letter opened them and inhaled the spores, they became infected. 5 out of 22 died.
    • Biological Warfare Debate
prevalence
Prevalence
  • In the past, anthrax was found all over the world.
  • Now, this bacterium is found mainly in underdeveloped countries lacking the means of disease control; such as the Middle East, Africa, Australia, southern and eastern Europe, South and Central America, Asia
  • It is not common in the United States, although small outbreaks periodically occur in agricultural areas on animals.
  • The last outbreak resulted in the death of 5 out of 22 people in 2001.
    • 1987: 20 out of 22 had died
  • 2,000 – 20,000 human outbreaks annually
susceptibility
Susceptibility
  • All warm-blooded animals are susceptible to anthrax, especially herbivores
    • Other domesticated animals such as horses and mules may also contract the disease.
treatment
Treatment
  • Cutaneous / gastrointestinal
    • Antibiotic therapy for 7 – 14 days
  • Inhalation
    • Antibiotic therapy for 30 days if used alone
    • If vaccine is available, antibiotics can be discontinued after 3 doses of vaccine
vaccine
Vaccine
  • Anthrax Vaccine Adsorbed (AVA)
    • 6-dose series at 0,2,4 weeks and 6,12,18 months
    • Annual booster injections to maintain immunity
  • Who receives vaccine?
    • Animals, mainly cattle
    • People with high occupational risk
      • Military, people close to an outbreak
prevention
Prevention
  • Decontamination
    • Wash down with anti-microbe effective soap
    • Boil articles that came in contact with infected hosts
    • Chlorine
    • Burning articles
  • Early detection
    • USPS installed BioDetection System
  • Antibiotics
    • Penicillin
    • Doxycycline
current research
Current Research
  • New research has found that extracellular metalloproteases may play a role in the survival of the bacterium
    • Aid in degradation of the LL-37 peptide.
    • Other bacillus species showed no resistance to this peptide
current research cont
Current Research cont.
  • Anti-protective antigen antibody has been shown to suppress the vegetative form of B. anthracis before it sporulates.
current research cont1
Current Research cont.
  • Research has also shown a new technique in identifying anthrax spores before a new outbreak occurs.
    • Microwave-Accelerated Metal-Enhanced Fluorescence (MAMEF) (Metal-enhanced flulow power microwave heating) is used to accelerate DNA hybridization
    • The DNA of the B. anthracis spores was detected almost immediately.
references
References
  • http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=17955147&ordinalpos=2&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum
  • Microbiology Lecture Textbook
  • http://www.cdc.gov/
  • http://www.nlm.nih.gov/medlineplus/anthrax.html
  • http://pathport.vbi.vt.edu/pathinfo/pathogens/Bacillus-anthracis.html
  • http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=191218&lvl=1
  • http://www.ncbi.nlm.nih.gov/sites/entrez
  • http://www.bt.cdc.gov/agent/anthrax/lab-testing/#references