Clostridium perfringens

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Clostridium perfringens

• Carl Kihm
• BI-331 Microbiology
• December 7, 2004

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Clostridium perfringens

• Relatively Large
• Anaerobic
• Gram-positive
• Spore-forming rods
• Found in the soil
• Member of the normal gut flora of humans
• Produce harmful toxins and hydrolytic enzymes
• Gangrene - Clostridium Myonecrosis
• Clostridial food poisoning

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Clostridium Myonecrosis

• Infection typically grows in a wound found on a
  limb that has an anaerobic area of dead tissue.
• Reduced blood flow to the wound leads to hypoxia.
  When the oxygen tension is low enough, C.
  perfringens undergo rapid growth in the ischemic
  tissue, and spread their enzymes and toxins to
  healthy surrounding tissue.
• This lack of blood supply results in dead,
  anaerobic tissue which is necessary for the
  anaerobic infection to spread.
• The enzymes are responsible for fermenting the
  tissues amino acids and fatty acids and
  producing a variety of end products
• The foul-smelling gas helps to split muscles
  apart and allows the infection to expand. When
  the appropriate conditions are present, the gas
  gangrene infection can spread throughout an
  entire limb within several hours.

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Clostridium Myonecrosis

• The five biotypes (A-E) of C. perfringens produce
  an assortment of over 20 different toxins.
• The a-toxin is produced in varying amounts by
  each of the five biotypes of C. perfringens and
  is considered to be the primary virulence factor
  involved with clostridium myonecrosis

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Clostridium perfringens a-toxin

• The crystal structure of a-toxin reveals a
  two-domain protein, the amino-terminal domain
  composed of a-helices joined by a flexible linker
  region to the carboxy-terminal domain of
  ß-sheets.
• The amino-terminal domain has phospholipase-C
  activity. The carboxy-terminal domain may have a
  key role in a-toxins membrane interaction and
  binding to phospholipids.
• Several of a-toxins exposed hydrophobic residues
  are believed to be located in the appropriate
  positions to interact with the fatty-aceyl tail
  groups of membrane phospholipids.

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Clostridium perfringens a-toxin

• Phospholipase-C, Sphingomyelinase-C
• Promotes membrane degradation by hydrolyzing
  phospholipids
• Products of the phospholipids hydrolysis rather
  than the actual degradation of cell membrane are
  responsible for the harmful effects
• Diacylglycerol activates PKC- activates
  membrane-bound phospholipases -IP3

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Other Clostridium perfringens toxins

• ßeta toxin
• Pore-former, functions similarly to a-toxin
• epsilon toxin
• Binds tightly to the plasma membrane of sensitive
  cells- does not enter the membrane. Through an
  unknown mechanism, the e-toxin is believed to
  affect cell membrane permeability.
• ?ota toxin
• A-B toxin -consists of a binding component (Ib)
  and an enzymatic protein (Ia), catalyzes the
  ADP-ribosylation of actin monomers.
• thet? toxin
• binds cholesterol in eukaryotic membranes, causes
  the complete hemolysis of red blood cells by
  forming oligomers which subsequently form pores
  through the cell membrane.
• ?appa toxin
• collagenase - can hydrolyze collagen molecules -
  destruction of blood vessels and connective
  tissues observed in clostridial myonecrosis.
• digma toxin
• selectively lyses cells, does not enter the cell
  membrane, the toxins exact mechanism of
  disruption is not known.

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Clostridium Myonecrosis

• C. perfringens also secrete a variety of
  hydrolytic enzymes that degrade extracellular
  substrates and cause cell lysis.
• act synergistically with toxins
• important role in providing nutrients for C.
  perfringens growth and also contribute to the
  disorganization of gangrenous lesions.

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Other Clostridium perfringens toxins
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Clostridium Myonecrosis

• In response to ischemia, tissues and macrophages
  release monocyte chemoattractant protein 1
  (MCP-1), a chemokine responsible for recruiting
  monocytes to the ischemic area.
• Macrophages release macrophage inflammatory
  protein 1 alpha (MIP-1- a) and tumor necrosis
  factor alpha (TNF- a). These cytokines lead to
  the recruitment of additional macrophages and
  polymorphonuclear leucocytes (PMNs) which have
  the ability to survive anaerobic conditions.
  However, due to the lack of blood supply to the
  infection, the macrophages can not reach the site
  of infection and are ineffective.
• Due to the same reason, antibiotics are unable
  move into the dead tissue spaces. The wound
  ultimately becomes a safe-haven for the bacteria.
  (anti-toxin treatment is more effective)

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Clostridium Myonecrosis

• Not all wounds exposed to C. perfringens become
  infected those infected usually have damaged
  blood vessels or heart problems
• Toxins can enter the bloodstream and cause damage
  to organs such as the kidneys. With an average
  incubation time of 10-48 hours, the infection can
  spread rapidly to the surrounding healthy tissues
  and organs. The expanding zone of infected dead
  tissue requires prompt and severe treatment
  amputatation

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Vaccine Development

• Vaccines have been developed from crude filtrates
  of C. perfringens however, a it is difficult to
  prepare immunogenic toxoids.
• Current efforts to develop an effective vaccine
  are minimal since the incidence of this disease
  is relatively small.

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• Blood agar plate with C. perfringens
• characteristic double zone of hemolysisalpha-toxi
  n incomplete outer zonetheta-toxin clear inner

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Clostridium perfringens
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