Corynebacterium diphtheriae   b.carl
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Corynebacterium diphtheriae b.carl






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Corynebacterium diphtheriae   b.carl Corynebacterium diphtheriae b.carl Presentation Transcript

  • Corynebacterium diphtheriae
  • General Characteristics
    • Gram Positive
    • Club shaped rod
    • Forms clusters of “Chinese-characters”
    • Aerobic
    • Non-spore forming
    • Exterior fimbriae
    • Contains no plasmids
    • Toxigenic and Non-toxigenic forms
  • Compound Light Microscope
    • The club or bar appearance of the cells is due to pockets of inorganic phosphate which form metachromatic granules when stained
  • Electron Microscope
  • Reservoir
    • Human Body
    • Normal flora of skin and nasopharynx
    • Enters upper respiratory tract and cutaneous
  • Transmission
    • Spread by inhalation of airborne bacteria
    • Direct contacted with an infected person
    • Open wounds
  • Virulence Factors
    • Diphtheria toxin
      • Diphtheria toxin gene is encoded by a bacteriophage
      • Phage Beta
      • DT inhibits of protein synthesis (elongation factor 2)
      • C. Diphtheria without this gene is not as harmful
    • Repressor (DtxR) gene, is activated by iron and prevents transcription of the tox gene
      • High iron levels = no toxin release
      • Low iron levels = toxins released
  • Clinical Diseases
    • Respiratory diphtheria is caused by C. diphtheriae bacteria adhering to and colonizing the tonsils, nasal cavity, and throat
    • Cutaneous diphtheria can be caused by both the toxigenic and the nontoxigenic strains of C. diphtheriae
      • Creates deep, erosive ulcers
    • If left untreated could damage the heart and nerves and eventually lead to death.
  • Identification/Diagnosis
    • Upper-respiratory tract illness characterized by sore throat, low-grade fever, and an adherent membrane of the tonsils, pharynx, and/or nose
      • Creates a pseudomembrane, a greenish-gray film that hardens in the pharynx from inflammation and can cause asphyxiation.
    • Sample of the bacteria is isolated from the patient’s throat/mouth and cultured
    • “ Bull Neck” appearance
    • To test for toxigenicity, the Elek test is performed
  • Symptoms
    • Cystine-Tellurite blood agar, incubated at 35 degrees C in A CO(2)-enriched atmosphere. Colonies of Corynebacterium diphtheriae on tellurite containing agar are gray-black, while most of the usual oral flora are inhibited.
  • Treatment
    • Diphtheria infection is treated with diphtheria antitoxin
    • Formalin eliminated the toxicity of DT without destroying its immunogenicity. Formalin-treated DT, now called diphtheria toxoid
    • 14-day course of antibiotics, preferably Erythromycin or Penicillin
  • Prevention
    • Tdap (Adults) or DTaP (Under 7 yrs old) Vaccines
      • combined vaccine against diphtheria, tetanus (Lockjaw), and pertussis (whooping cough)
    • Children should get 5 doses of DTaP vaccine, one dose at each of the following ages:
      • 2 months
      • 4 months
      • 6 months
      • 15-18 months
      • 4-6 years
  • Prevention (cont.)
    • Tdap
      • A single dose of Tdap is recommended for people 11 through 64 years of age.
    • Td
      • Td , protects only against tetanus and diphtheria
      • recommended every 10 years.
  • Questions
    • What is a common symptom of a toxigenic C. diphtheriae infection?
    • a) Chickens Neck
    • b) Bulls Neck
    • c) Giraffe’s neck
    • d) None of the Above
    • C. diphtheriae infection is treated with:
    • a) antibiotics
    • b) antitoxins
    • c) no treatment except replenish water
    • d) both a and b
  • References
    • Mandlik, A., Swierczynski, A., Das, A. and Ton-That, H. (2007), Corynebacterium diphtheriae employs specific minor pilins to target human pharyngeal epithelial cells. Molecular Microbiology, 64: 111–124. doi: 10.1111/j.1365-2958.2007.05630.x
    • Holmes, R.K. (2000) Biology and molecular epidemiology of diphtheria toxin and the tox gene. J Infect Dis 181 (Suppl. 1): S156–S167.
    • Coordinating Center for Infections Diseases/Division of Bacterial and Mycotic Diseases "Diphtheria" 6 October 2005
    • Todar, Kenneth, University of Wisconsin-Madison Department of Bacteriology, "Diphtheria" 2002
    • National Center for Immunization and Respiratory Diseases: Division of Bacterial Diseases, “Diphtheria” February 7, 2011