1. Host Microbe Relationship Patricia Sidelsky 2007

2. Microbe host relationships  Symbiosis – Coexistence of two or more organisms to the success of the other in the environment. Can evolve specific mechanisms to maintain this relationship 1. Mutualism 1. Mutualism 2. Commensalism 2. Commensalism 3. Parasitism 3. Parasitism

3. Mutualism  Both partners in a relationship are dependent upon each other  Each contributes to the success of the other organism in a particular environmemt

4. Rhizobium and legumes

5. Coral and Zooxanthellae

6. Coral Bleaching can lead to death of the reef

7. Leaf cutter ants

8. Ruminants - Gut reactions: Sequencing ruminal bacteria

9. Commensalism  Microbes that share space on the skin as well as the metabolic products  Coexist – the partners in the relationship do not contribute to the success of their fellow microbes, but neither are they harmed

10. E. Coli in the gut  E. coli lives in an enriched environment high in nutrients  In return E. coli produces Vitamin K for blood clotting

11. Parasitism and Pathogens  Pathogens are disease producing organisms  The parasite benefits from the relationship  The host is harmed  +/- relationship

12. Flat worms - Platyhelminthes  Cestodes  Trematodes

14. Schistosomiasis

15. Schistosomes

17. Clinorchis senensis - Liver

18. Tapeworm

19. Tapeworm

20. Protozoan parasites – Plasmodium vivax and Plasmodium falciparum

21. Giardia lamblia

22. Entamoeba histolytica

23. Key terms  Infection refers to the presence or a parasitic organism or pathogen( implies that they are established and reproducing)  Infestation – A word usually limited to larger parasites like helminths or worms  Contamination – refers to the presence of microbes( can be on the surface of an inanimate object )

24. Disease  Disturbance in the state of health that may result in the infection of human tissue by microbes  Changes in the host that interfere with normal function  Fever, diarrhea, inflammation, irreparable damage

25. Pathogenicity  Ability to produce disease  Invasion of pathogen  Release of molecules by pathogen  Host response to invader

26. Relationships  Normal flora – normal microbiota – Many organisms have well established associations with humans  Resident microbiota – microbes that are always present – skin, orifices, interior of nose and throat – Tend to colonize mucous membranes

27. Transient microbes  Present under certain conditions  May require special nutrients  Not as adaptive OPPORTUNISTIC ORGANISMS MAY BE TRANSIENT

28. Opportunistic organisms  Able to penetrate the immune defenses if there is another infectious agent present  Immunocompromised due to malnutrion or other extenuating factor  Introduced at an inappropriate body site  Imbalance of the normal flora due to antibiotic therapy  Imbalance of the normal flora due to chemotherapy

29. Candida

30. C. difficile

31. Burkholderia cepacia

32. How Microbes Cause Disease  Adherence  Colonization  Invasiveness  Virulence factors and Toxins  Growth and Multiplication in the host  Exiting the host  Cell injury and destruction

33. Adherence  Adhesins - molecules that are adhesive in nature and are found on the tips of the fimbriae  These adhere to the host cell membrane( specificity involved between pathogen and host)

34. Receptors that are specific for infective agents  CCR5 receptor on macrophages that binds to both bacteria and viruses  Yersinia pestis - causative agent of the plague  HIV- causative viral agent of AIDS

35. CCR5 receptor

36. Anthrax and receptors

37. Invasiveness  Ability to grow in the host  To spread through tissues  To avoid the immune defenses

38. Virulence factors  Hyaluronidase – enzyme that breaks down connective tissue. Break down of connnective tissue insures that the streptococci can spread through epithelial tissues lining the throat

39. Coagulase( staphlococcus aureus)  Causes blood to clot – fibrin clot protects the bacteria  Walls off microorganisms so that they can avoid macrophages and neutrophils

40. Streptokinase  Dissolves blood clots  Pathogens trapped in blood clots are freed

41. Exotoxin or endotoxin  Exotoxins secreted or released by bacteria into the host tissues  Endotoxins – Molecules present in the cell wall or exterior covering of a bacterium

42. Hemolysins( Exotoxins)  Burst red blood cells and release hemoglobin to be used for the cell’s metabolism  Alpha  Beta ( clear area around bacteria on blood agar) page 397  Gamma

43. Exotoxins against WBC  Leukocidins – release by strep and staphylococci – destroys white blood cells that are able to phagocytosed bacteria

44. Neutrophil and infection

45. Endotoxins  LPS ( A antigen)  Produced by Gram negative organisms  Endotoxins released when bacteria are killed by antibiotic  Can cause severe reaction