Anthrax Bacillus anthracis

Document Sample
Anthrax Bacillus anthracis Powered By Docstoc
					Anthrax: Bacillus anthracis

                    Kimberly Covert
                    BIO 488
     Basics of Anthrax
• Bacillus anthracis causes anthrax
• Became a growing concern after 5
  people died in 2001 through the
  bioterrorist attack delivered through
  the US Postal Service
• Found commonly as an
  environmental pathogen
• Can be weaponized but is expensive
  and dangerous
What does it look like?

         Electron Micrograph of a
         monkey RBC and the
         rod-shaped B. anthracis
     The Mighty Spore-former
                                                         • B. anthracis is a spore-
                                                           forming bacteria and has a
                                                           polyglutamic acid capsule
                                                         • It commonly causes
                                                           infections in grazing
                                                           species of vertebrates such
                                                           as cows, goats, and sheep
                                                         • Can be transmitted to
                                                           humans, although rare,
                                                           through ingestion of
                                                           spores, eating
                                                           contaminated meat, or     through a bioterrorist attack
       On the Plus Side
• Anthrax cannot be spread from human to
• Cases in the Unites States are rare; about
  2 cases a year are reported
• Is mostly a disease found in developing
• Laboratory growth of B. anthracis is
  difficult and most experts do not forsee it
  being used as a large scale biochemical
  The Types of Infection
• There are three types of infections

  – Cutaneous

  – Inhalation

  – Gastrointestinal
   Cutaneous Infections
• Most common making up 95% of
• Bacterium enters the body through a
  break in the skin
• Transmitted though the handling of
  animal products
• Initial infection resembles a bug bite but
  will develop into a painless ulcer
• May also cause swelling of local lymph
         Cutaneous Anthrax

                                                              In cases that go
                                                              untreated the
                                                              mortality rate is
                                                              about 20%

                                                              Death is rare with
                                                              the use of
     Inhalation Anthrax
• Transmission is through the
  inhalation of anthrax spores
• This is the type that was used in the
  2001 bioterrorist attack
• Manifests as a common cold and
  progresses to severe breathing
  problems and shock
Inhalation Anthrax

         Inhalation anthrax is
         usually fatal
         This picture shows
         the lung tissue of a
         patient infected with
         inhalation anthrax
         The red arrow points
         to the infective spores
Gastrointestinal Anthrax

• Transmitted through eating of
  undercooked contaminated meat or
  animal products
• Results in acute inflammation of the
• Causes nausea, vomiting, and
  diarrhea which become more severe
  with time
    Gastrointestinal Anthrax

                                                              The mortality rate of
                                                              patients infected with
                                                              Gastrointestinal Anthrax is
                                                              anywhere from 25-60%

                                                              This is a picture of the
                                                              intestines of a patient that
                                                              died from Gastrointestinal

                                                              There is severe edema and
 The Immune Response
• B. anthracis is an extra-cellular
• The polyglutamic acid capsule is
• Typical anti-body players
  – Monoclonal Ab response
  – IgG
  – IgA (nasal entry for inhalation anthrax)
  – IgM
 The Immune Response

• Systemic and mucosal anti-toxin
  responses are typical
• There are high levels of IgG and IgM
  in the serum
• There are high levels of IgA in the
  secretions of the upper and lower
  respiratory tracts
 The Immune Response
• The anthrax toxin also induces the
  release of inflammatory cytokines
  – IL-1β
  – IL-6
• IL-6 directs a Th2 response
  promoting B-cell proliferation
• IL-1β activates macrophages and
  contributes to inflammation
       Immune Evasion
• Two of the toxin components edema
  factor and lethal factor can suppress the
  immune system
• The inhibit:
  – proliferation of T lymphocytes
  – the release of inflammatory cytokines
  – the activation of macrophages and dendritic
• Inhibition is mediated through blocking
  kinase signaling pathways necessary for
  the activation of the cells
   Detection of Anthrax
• Anthrax spores are not able to be
  seen by the naked
• They have no distinct odor or taste
• However in weaponized form, they
  must be suspended in a powder
• Most of the signs and symptoms are
  flu-like but there is no runny nose
  with an anthrax infection
Testing for Anthrax Exposure

• There are no definitive testing methods to
  determine if a person has contracted
• Nasal swabs and environmental testing
  are done to determine exposure but not to
  determine treatment
• No every exposed person will contract a
• Signs and symptoms are what determines
Laboratory Identification

• Staining of the capsule with
  methylene blue
• Non-fastidious
• Non-hemolytic on horse blood agar
  whereas many other species of the
  Bacillus genus are hemolytic
               The Toxin
• The lethal affects of a B. anthracis
  infection are mediated by a toxin
• The toxin has 3 parts
   – A lethal factor (LF)
   – An edema factor (EF)
   – A protective antigen (PA)
• PA transports LF and EF to the cytosol of
  cells where they do their damage
• The protective antigen is used to induce
           The Vaccine
• The vaccine for anthrax is a toxoid
• The Protective Antigen (PA) is the toxoid
• After injection, immunity to the PA is
• Since PA is disabled, the anthrax toxin
  cannot be transported into the cell to do
• The vaccine is administered at 0, 2, and 4
  weeks. Then again at 6, 12, and 18
  months with annual boosters following.

• The vaccine is not generally made
  available to the public
• Only those persons who are at a
  high risk of exposure should be
• Antibiotics are sufficient post-
  exposure in most cases
        Who is at risk?
• Military personnel
• Laboratory workers who come into
  contact with the organism
• Those who work with imported
  animal furs and hides
• Anyone who handles animal
  products that are at a high potential
  of contamination
• There are several prescription drugs
  prescribed for anthrax infections
• For inhalation and gastrointestinal
  anthrax and for severe cases of
  cutaneous anthrax multiple antibiotics are
• The main drugs are
  –   Ciprofloxacin (main)
  –   Doxycycline (main)
  –   Penicillin
  –   Erythromycin
  –   Chloramphenicol
• Is part of the tetracycline class of
• Inhibits protein synthesis
• Inhibits the normal flora
• Common side effects include upset
  stomach, vomiting, and diarrhea
• Should not be take by children or
  pregnant women because it
  suppresses bone growth
• Belongs to the family of Quinolone
• Inhibits nucleic acid synthesis
• Side effects include, nausea,
  vomiting, diarrhea, dizziness, and
• Are not recommended for children
  and pregnant women because it
  suppressed the growth of catilage
  Should we stock pile?
• Most experts agree that the risk of a large
  scale bio-terrorist attack is low and
  stockpiling of antibiotics is unnecessary
• A stockpile may be created that will be
  used against numerous bioterrorist
  agents including anthrax
• If a stockpile were to be created,
  doxycycline is recommended over cipro
  because it is less expensive and there is
  less immunity in B. anthracis and other
  bioterrorist agents
More Research on the Toxin

• The 3D crystal structure of the PA and
  one of the binding sites on human cells
  CMG2 bound together has recently been
• This discover give scientists more of an
  idea of how the two interact and how to
  shut down the interaction
• Another possible outcome of the
  discovery is the using an altered anthrax
  toxin to attack tumor cells
          Tumor Attack
• Researchers believe that the CMG2
  receptor is very similar to the other
  receptor on human cells, TEM8
• TEM8 is usually found in the cells lining
  the blood vessels of tumors
• If an altered toxin with an affinity only for
  TEM8 could be produced, it would be
  selectively toxic for the tumor cells and
  have no effects on normal cells
• In effect, the toxin would be able to kill the
   What’s the big deal?
• Anthrax and bioterrorism are part of
  a bigger controversial issue
• Many people seem to be highly
  concerned with bioterrorism
• The government has restricted
  access to many dangerous
  pathogens and research has
  become far more restricted
          The Big Deal
• The greatest concern comes from the
  publishing of techniques that could
  potentially aid terrorists in mass
  producing toxic biological agents
• The paper published on the recreation of
  the 1918 strain of influenza raised many
  ethical questions about who should be
  allowed to reproduce dangerous
  pathogens and if the methods should be
  open the public
         The Big Deal
• The previous terrorist attacks were
  not exacted on a mass scale and not
  well thought out
• The biggest question remains, do
  terrorist groups have the funding and
  the personnel to carry out a large
  scale attack?
• Are we aiding them in learning how
  to created and distribute a
  biochemical weapon?

• Websites:

  – The Centers for Disease Control
  – The New England Journal of Medicine
  – The National Institutes of Health

• Brouillard, J.E. et al. 2006. Antibiotic selection and
       resistance issues with fluoroquinolones and
       doxycycline against bioterrorist agents.
       Pharmacotherapy. 1:3:3-14.

• Comer, J.E. et al. 2005. Direct inhibition of T-lymphocyte
     activation by anthrax toxins in vivo. Infection and
     Immunity. 73:12:8275-81.

• Hanson, J.F. et al. Neutralizing antibodies and persistence
      of immunity following anthrax vaccination. Clinical
      Vaccine Immunology. 13:2:208-213.

• McConnell, M.J. et al. Cytokine response and survival of
     mice immunized with an adenovirus expressing
     Bacillus anthracis protective antigen domain 4.
     Infection and Immunity. 74:2:1009-15.
• Petro, J.B., Relman, D.A. 2003. Understanding threats to
       scientific openness. Science. 302:1898-1898.

• Pittman, P.R. et al. 2006. Patterns of antibody response in
       humans to the anthrax vaccine absorbed (AVA) primary
       (six-dose) series. Vaccine. Feb 9 (Epub ahead of print).

• Santelli, E. et al. 2004. Crystal structure of a complex between
      anthrax toxin and its host cell receptor. Nature.

• Sloat, B.R., Cui, Z. 2006. Strong Mucosal and Systemic
       Immunities Induced by Nasal Immunization with Anthrax
       Protective Antigen Protein Incorporated in Liposome-
       Protamine-DNA Particles. Pharmaceutical Research.

• Xu, J.J. et al. 2005. Toxin-neutralizing monoclonal
       antibodies to the different domains of anthrax protective
       antigen. Wei Sheng Wu Xue Bao. 45:6:947-51.