Nature and Properties of Micro-organisms

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Nature and Properties of Micro-organisms

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Smallest to largest….. Prions Viruses Bacteria Fungi

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Nội dung Text: Nature and Properties of Micro-organisms

  1. Nature and Properties of Micro-organisms Laura JV Piddock
  2. Smallest to largest…..  Prions  Viruses  Bacteria  Fungi
  3. Prions  Infectious protein  No DNA or RNA  Normal cellular form of protein vs. pathological form Pathological form found in neural tissue and tonsils PrP-C & PrP-Sc
  4. Pathology  Spongiform encephalopathy: transmissible, familial  Transmission: oral, operative (neural tissue, dura, corneas), ??? blood  Resistance to disinfectants  Formaldehyde increases infectivity
  5. Viruses  DNA or RNA  Shell of protein (capsid) surrounding nucleic acid  Classification on basis of nucleic acid DNA viruses: eg Herpes simplex virus (HSV) RNA viruses: eg influenza virus
  6. DNA viruses: herpes simplex virus (HSV)
  7. RNA viruses: Influenza
  8. Viruses Obligate intracellular parasites Use host cell for nucleic acid and protein synthesis Cell attachment: target for blocking antibody vaccines Intracellular replication: target for antiviral drugs n.b. retroviruses (RNA) e.g. HIV RNA  DNA
  9. Viral effects on host cells  Degeneration (cytopathic effect): CMV  Cell lysis  Cell fusion, syncytia formation: RSV  Cell proliferation  Transformation: malignancy (parvoviruses)  Latent infection - no sign of infection until reactivation  ‘cold sores’ (HSV)  chickenpox  shingles (VZV)
  10. CMV hepatitis owl eye effect inclusion body
  11. Varicella zoster virus (VZV) VZV: Chickenpox VZV: Shingles Re-activation of latent infection Suppression of cell mediated immunity
  12. Bacteria  Unicellular, prokaryotes  DNA and RNA  Binary fission  No mitochondria  Rigid cell wall containing peptidoglycan
  13. Eubacteria  Classified according to:  size & shape  cell wall (Gram stain)  aerotolerance  Gram stain reaction  positive - purple  negative - pink  Shape  coccus - round (chains? clusters?)  bacillus - rod
  14. Wound swab: S. aureus
  15. Neisseria gonorrhoeae Gram stained urethral discharge. The image shows many polymorphonuclear leukocytes (PMNs) and gram-negative extra- and intra-cellular diplococci. (1,000X oil)
  16. Pneumococci in sputum
  17. Other important bacteria  Strict anaerobes: e.g. Bacteroides fragilis  metronidazole sensitive  ‘Higher bacteria’ e.g. Mycobacterium tuberculosis  Spirochetes eg Treponema pallidum (syphilis)
  18. M. tuberculosis causes TB  M. leprae causes leprosy complex cell wall (acid-alcohol fast bacilli; AFB)
  19. Treponema pallidum
  20. Unusual bacteria  Mycoplasma  E.g. Mycoplasma pneumoniae (pneumonia)  lack peptidoglycan - resistant to penicillins  Chlamydiae  E.g. Chlamydia trachomatis (trachoma; NSU)  obligate intracellular parasite  needs host ATP
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