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Nature and Properties of Micro-organisms

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Nature and Properties of Micro-organisms

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    1. Nature and Properties of Micro-organisms Laura JV Piddock

    2. Smallest to largest�.. Prions Viruses Bacteria Fungi

    3. Prions

    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

    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)

    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

    17. Other important bacteria Strict anaerobes: e.g. Bacteroides fragilis metronidazole sensitive �Higher bacteria� e.g. Mycobacterium tuberculosis Spirochetes eg Treponema pallidum (syphilis)

    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

    21. Chlamydia trachomatis

    22. Important bacterial cell components 1: (endo)spores.

    23. Gram positive, bacillus, anaerobic, spores

    24. Important bacterial cell components 2: Flagella

    26. Important bacterial cell components 3: Pili (Fimbrae)

    27. Important bacterial products 1: extracellular polysaccharide

    29. Important bacterial products 2: Exotoxins: secreted by Gram positive bacteria E.g. C. tetani active immunity - toxoid passive immunity - antitoxin

    30. Bacterial cell walls

    31. Important cell wall components 1 Peptidoglycan: synthesis is target for penicillins, cephalosporins and vancomycin Gram positives: lipoteichoic acid, septic shock Beta-lactamases hydrolyse penicillins and cephalosporins secreted by Gram positive bacteria Within periplasm of Gram negative bacteria

    32. Important cell wall components 2 LPS, Endotoxin

    33. Fungi Eukaryotes Rigid chitinous cell walls Antifungal drugs interfere with cell wall synthesis Classified morphologically: moulds - filamentous, spore-forming eg Penicillium, Aspergillus yeasts - unicellular, budding reproduction eg Candida, Cryptococcus

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