1 / 74

Infectious diseases

Infectious diseases. What is a pathogen?. What is a pathogen?. Pathogen- from Greek pathos (emotion/suffering) ; gene – to give birth to An agent causing illness or disease in the host/ an infectious particle able to produce disease. Are all pathogens infectious?. Not necessarily.

gerek
Télécharger la présentation

Infectious diseases

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Infectious diseases

  2. What is a pathogen?

  3. What is a pathogen? Pathogen- from Greek pathos(emotion/suffering); gene – to give birth to An agent causing illness or disease in the host/ an infectious particle able to produce disease

  4. Are all pathogens infectious? • Not necessarily

  5. Infectious agents • Pathogenic bacteria • Pathogenic viruses (not considered organisms) • Pathogenic fungi • Pathogenic protists (protozoa) • Pathogenic parasites – e.g. helminth worms • Pathogenic prion (not organisms)

  6. What are the top ten infectious diseases? 10. Smallpox 9. Typhoid 8. Influenza 7. Bubonic Plague 6. Cholera 5. Anthrax 4. Malaria 3. SARS Coronavirus 2. EBOLA or Nantahaemorrhagic virus 1. HIV

  7. WHO

  8. Non-specific defences: External Defences 6.3.3: Outline the role of skin and mucous membranes in defence against pathogens

  9. Routes of infection

  10. Innate Immunity: commensal (non-pathogenic) bacteria • Of the 100 billioncells in our bodies, only 10 billion are actually human cells! • The rest are commensal bactseria, fungi, protozoa and even arhropods! • They perform essential housekeeping functions in our bodies…

  11. Summary of external defences Anatomical Defences • skin • mucous membranes Body secretions/excretions • mucous • tears, saliva, urine (wash-out) • Lysozyme (antibacterial enzymes) in tears/nose/saliva • lactoperoxidase in breast milk • Acidic pH (sweat, urine, gastric fluid, vaginal secretions) • Zinc and spermine in semen Normal commensal flora • Inhibitory substances • Compete for nutrients Cilia Mucociliary escalator in respiratory tract

  12. Drug treatment of infection – Antibacterials, Antifungals and antiviral treatments

  13. Antibiotics • Many antibiotics are naturally produced by saprotrophic organisms (fungi and bacteria) in order to compete for the dead organic matter on which they feed • Many antibiotics are produced by fungi, to inhibit bacterial growth • Some antifungals are produced by bacteria to inhibit fungal growth

  14. Culture and sensitivity testing

  15. How do antibiotics work? • Antibiotics block metabolic pathways which are specific to bacterial or fungal cell metabolism/replication (but are absent or different in eukaryotic animal cells): • Cell wall synthesis • Cell membrane function • DNA replication • Transcription and translation of RNA (remember that the 70 S prokaryote ribosome differs from the eukaryotic 80 S ribosome)

  16. How do antibiotics work? • A great wee animation

  17. Antibiotics can be bacteriostatic OR bactericidial Bacteriostatic drugs inhibit replication and growth of the bacteria (maintain bacteria in a stationary phase of growth): • May act on cell metabolism – specific prokaryotic enzymes • May inhibit DNA replcation, transcription or translation • Work in concert with the immune system • (Chloramphenical, macrolides, tetracyclins) Bactericidal drugs KILL bacteria • May disrupt the integrity of the cell wall • May act on essential metabolic pathways – specific prokaryotic/fungal enzymes

  18. The definition bacteriostatic/bacteriocidal is an oversimplification • It depends on the DOSE of drug used • It depends on the efficacy of the host innate defence system • It depends on ability of the drug to penetrate the infected tissue (e.g cross the blood brain barrier in meiningitis, penetrate bronchial secretions in pneumonia, penetrate cells for intracellular bacterial infection)

  19. Antibiotics were (once) miracle drugs • the paradox of the antibiotic miracle drug

  20. Do antibiotics work on viruses? Obviously not!!! This hyperlink introduces the whole complicated world of viral replication…

  21. Antiviral agents Acyclovir Highly specific for Herpes Viruses – disables viral DNA replication Tamiflu Specific for Flu virus May accelerate alleviation of symptoms by 12 h Resitance has been recorded

  22. Interferon Treatment • Interferon is a naturally produced protein (cytokine) which is produced in response to viral infection • It has been used for treatment of HIV, Hepatitis C and certain types of cancer

  23. Innate immunity begins with the inflammatory response • the inflammatory response

  24. Blood components Involved in allergic reactions Respond to parasitic infections

  25. Phagocytes • Neutrophils (polymorphonuclear neutrophils)(most abundant, 60 – 70%) • Macrophages: circulating or ‘marginal’ (Big devourers) • Dendritic Cells

  26. Phagocytes

  27. Macrophages

  28. Neutrophils • Most common type of white blood cell (50 – 70%) • Phagocytic – but die immediately! • First immune cells to reach a site of infection – attracted by chemotaxis • PUS is made of dead neutrophils (that’s what makes pus white…)

  29. Dendritic Cells

  30. A dendritic cell slide show… • Dendritic Cells are beautiful...

  31. Phagocytosis (1)

  32. Phagocytosis (2)

More Related