1 / 39

GENERAL ASPECTS OF BACTERIAL PATHOGENESIS Lecture 33

GENERAL ASPECTS OF BACTERIAL PATHOGENESIS Lecture 33. Faculty: Dr. Alvin Fox. Key Words. Pathogen Transmission Outbreak, Epidemic, Pandemic Adhesion Normal flora Penetration Infection Invasiveness/spread

wilkinson-junior
Télécharger la présentation

GENERAL ASPECTS OF BACTERIAL PATHOGENESIS Lecture 33

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. GENERAL ASPECTS OF BACTERIAL PATHOGENESIS Lecture 33 Faculty: Dr. Alvin Fox

  2. Key Words Pathogen Transmission Outbreak, Epidemic, Pandemic Adhesion Normal flora Penetration Infection Invasiveness/spread Infectious diseases Extra/intra cellular pathogen Compromised host Exotoxin Opportunistic infection Endotoxin - non-specific immunity Nosocomial Specific immunity Koch’s postulates Autoimmunity Bioterrorism

  3. Pathogenicity • virulence factors • number of initial organisms • immune status

  4. Pathogens • The “usual” rate • Oubreak - local • Epidemic - regional/national • Pandemic – widespread (international) • infections “beyond the norm”

  5. Koch's postulates • isolated • diseased not healthy people • growth • pure culture • induce disease • susceptible animals • re-isolated • susceptible animals

  6. Opportunistic infections • normal flora • environment • often compromised individuals

  7. Opportunists - normal flora • Skin • Staphylococcus aureus • Staphylococcus epidermidis • Propionibacterium acnes • Intestine • Bacteroides • high numbers • Enterobacteriaceae • low number

  8. Opportunists - environment • air • water • soil • food

  9. Opportunists • Community-acquired • Nosocomial - hospital

  10. Transmission • airborne droplets • food • water • sexual contact

  11. Host defenses • Gut • peristalsis • defecation • respiratory tract • ciliary action • coughing • sneezing • urogenital tract • urination

  12. Adhesion BACTERIUM adhesin receptor EPITHELIUM

  13. S. pyogenes F-protein lipoteichoic acid fibronectin

  14. E. coli Fimbriae Flagella

  15. E. coli fimbriae Type 1 mannose P • galactose • glycolipids • glycoproteins

  16. Penetration and spread Epithelium Blood stream Salmonella typhi Salmonella enteritidis Vibrio cholerae Gut lumen

  17. Connective tissue destrction • Helps bacterial dissemination • collagenase • hyaluronidase

  18. Extracellular pathogens • resistant to extra-cellular killing • killed on phagocytosis • resist killing • by avoiding internalization

  19. Protein A inhibits phagocytosis PHAGOCYTE Fc receptor Protein A immunoglobulin BACTERIUM

  20. r r r M protein inhibits phagocytosis Complement fibrinogen M protein peptidoglycan

  21. Intracellular parasite Bacteria Macrophage or neutrophil Lysozome Phagosome Enter cytoplasm Fusion No fusion

  22. Killing of intracellular parasite • Cell mediated immunity

  23. Tissue Injury • exotoxins • endotoxins and non-specific immunity • - no antigen • specific immunity • - antigen

  24. Exotoxins • proteins • usually enzymes • destroy cellular structures • destroy extracellular matrix

  25. A-B toxins Cell surface Active Binding A B

  26. Diphtheria toxin and Pseudomonas exotoxin A • ADP-ribosylates elongation factor (EF2) • inhibits protein synthesis • kills cells, destroys tissues

  27. Cholera toxin and E. coli labile toxin • ADP-ribosylation of regulator • adenylate cyclase activation • cyclic AMP • active ion and water secretion • diarrhea

  28. Shiga toxin - shigellosis • Shiga-like toxin – enterohemorrhagicE. coli • lyses 28S rRNA in ribosome • death of epithelial cells • poor water absorption • diarrhea

  29. Botulinum toxin • inhibits acetylcholine release • inhibits nerve impulses • muscles inactive • flacid paralysis • Tetanus toxin • inhibits glycine release • inactivates inhibitory neurons • muscles over-active • rigid paralysis

  30. Exotoxins - extracellular matrix of connective tissue • Clostridium perfringens • collagenase • Staphylococcus aureus • - hyaluronidase

  31. Membrane damaging exotoxins • Proteases • Phospholipases • Detergent-like action

  32. C. perfringens phospholipase • destroys blood vessels • stops influx inflammatory cells • creates anaerobic environment • allows growth of this strict anaerobe.

  33. Exotoxins • Antibodies (anti-toxins) neutralize • vaccination

  34. Endotoxin • Lipopolysaccharide - endotoxin • peptidoglycan -endotoxin-like action • cell envelope components • not proteins/enzymes

  35. Septic shock • hypotension (tissue pooling of fluids) • disseminated intravascular coagulation • fever • lack of effective oxygenation • overall system failure

  36. Endotoxins • non-specific inflammation • cytokine release • complement activation • B cell mitogens • polyclonal B cell activators • adjuvants

  37. Specific immunity and immunopathology • chronic infection • tuberculosis • leprosy • syphilis • persisting bacterial remnants • autoimmunity

  38. IgA proteases • help survival on external surfaces • H. influenzae • S. pneumoniae • N. gonorrhoeae • N. meningitidis

  39. Bioterrorism • air • most common • no previous exposure • zoonoses • manifest initially • colds/flu-like • death or debilitation • recognition • clinically (e.g. common source clusters) • clinical microbiology • biodetection (environment) • future

More Related