Principles of Disease

1. Principles of Disease Microbiology 2314

2. Every disease is a race between a pathogen trying to gain a foothold and the host defenses trying to prevent the pathogen from doing so.

3. Disease • Is a Process • Is a State of Being Not In Good Health • Involves Many Factors - Age - Nutrition - Gender - Race

4. We tend to equate one pathogen with one disease, but it is more complicated than that.

5. It is actually much more complicated than that.

6. Definitions: Parasite • Refers to Protozoans and Worms

7. Definition: Pathogen • Refers to Bacteria / Virus / Fungus • An organism with the potential to cause disease.

8. More Definitions: • Infection A pathogen growing in or on the host • Virulence The degree or intensity of pathogenicity • Invasiveness Ability to spread to other tissues • Infectivity Ability to secrete toxins • Septicemia Blood infection

9. Pathology Scientific study of disease • Etiology Cause of disease • Pathogenesis Development of disease • Host Organism that shelters and supports the growth of pathogens.

10. Disease • An abnormal process in which part or all of the body is not properly adjusted or is incapable of performing normal functions often because of infection by pathogens.

11. Relationships Between Microorganisms and Man • Usually germ-free in utero • Microorganisms begin colonization in and on the surface of the body during and after birth • We require these organisms • Germ-free organisms are less healthy than organisms with normal microbiota David Vetter the “Bubble Boy”

12. Body Regions Have Characteristic Flora • Skin 1012 • Mouth 1010 • GI Tract 1014

14. Normal Flora Are Found Mostly • on the skin • in the eyes • in the nose • in the mouth • in the upper throat • in the lower urethra • in the lower intestine • especially in the large intestine • Note that this list basically includes all of the body surfaces exposed to the external environment.

15. Microbial Antagonism • Normal Microbiota establish permanent colonies inside or on the body without producing disease • Symbiosis • Three Types 1. Commensalism 2. Mutualism 3. Parasitism • Transient microbiota are members of the normal flora that are not always present or are present for only a few days, weeks, or months before disappearing.

16. Nitrogen Fixation -- Mutualism

17. Ruminants and Resident Microbes – Mutualism

18. Lichen Symbiosis -- Mutualism

19. Ascaris Worms / Parasitism

20. The upper respiratory tract consists of the nostrils, nasal cavities and throat.  It contains a number of commensalistic inhabitants including:  Staphylococcus epidermidis. Out of all types of symbiotic bacteria, commemsalists are the least studied.  The reason for this is simple; if a bacteria is not causing harm or benefit to a host there is simply not much reasons to studying it.

21. Microbial Antagonism Microbial Antagonism or Colonization inhibition: A process by which pathogenic microorganisms are inhibited by normal flora from colonizing healthy organisms (a form of symbiosis) Antagonism between the fungus Paraconyothyrium variabile and Fusarium oxysporum

22. Mechanisms by which this inhibition occurs includes: 1. competing with pathogenic microorganisms for nutrients 2. competing with pathogenic microorganisms for space 3. producing toxins that are harmful to some pathogenic microorganisms

23. Remember! • Categorizing symbiotic relationships is convenient, but keep in mind that under certain circumstances the relationship can change.

24. Question? • A colonic microorganism which bores into its host and by doing so does it damage, competes with its host for nutrients, but is the sole supplier of an organic growth factor without which the host could not survive. This symbiotic relationship is an example of (chose the best answer): a. commensalism b. mutualism c. parasitism

25. Question? • A colonic microorganism which bores into its host and by doing so does it damage, competes with its host for nutrients, and is the sole supplier of an organic growth factor without which the host could not survive. This symbiotic relationship is an example of (chose the best answer): a. commensalism b. mutualism c. parasitism

26. Question? • A bacteria is attached to the intestinal wall via its pili, causes its host no harm, and secretes an antibacterial poison which limits colonization of the intestine by other, unrelated bacteria. With regard to the prevention of disease, what process specifically is this bacteria effecting?

27. Microbial Antagonism

28. Question? • Microbial antagonism (choose best answer) a. is a parasitic interaction between two organisms b. describes generally the harm done by a microorganism to a host c. can be an example of mutualism d. can be an example of parasitism e. all of the above Ab. none of the above

29. Question? • Microbial antagonism (choose best answer) a. is a parasitic interaction between two organisms b. describes generally the harm done by a microorganism to a host c. can be an example of mutualism d. can be an example of parasitism e. all of the above Ab. none of the above

30. Question? • A colonic microorganism which bores into its host and by doing so does it damage. This organism has no additional redeeming characteristics. You would describe the symbiotic relationship it has with its host as an example of (choose the best answer): a. commensalism b. mutualism c. microbial antagonism d. parasitism e. none of the above

31. Question? • A colonic microorganism which bores into its host and by doing so does it damage. This organism has no additional redeeming characteristics. You would describe the symbiotic relationship it has with its host as an example of (choose the best answer): a. commensalism b. mutualism c. an effector of microbial antagonism d. parasitism e. none of the above

32. Question? • Which is not a member of the normal flora of a plant or an animal? (assume all are obligate colonizers of the plant or animal host organism) a. a bacterium b. a virus c. a fungus d. a protozoa e. all are equally likely to be members of normal flora

33. Question? • Which is not a member of the normal flora of a plant or an animal? a. a bacterium b. a virus c. a fungus d. a protozoa e. all are equally likely to be members of normal flora

34. Question? • Name a part of the body that you would notexpect to have an associated normal flora.

35. StomachKidneyLiverEtc.Anything Basically That Is Internal

36. Transient Microbiota • Transient microbiota are members of the normal flora that are not always present or are present for only a few days, weeks, or months before disappearing.

37. Opportunistic Microorganisms • Do not cause disease under normal conditions but can cause disease under special conditions. Staph Infection

38. Cooperation Among Microorganisms • One of the organizing principles of life on Earth is that cells cooperate. • This is evident in the case of multicellular organisms, from nematodes to humans, but it also appears to apply widely among single-celled organisms such as bacteria, fungi, and amoeba.

39. A well-studied example of intraspecies cooperation concerns the cyanobacterium Anabaena, which grows in long chains, in which approximately one cell out of ten differentiates into a heterocyst that provides fixed nitrogen for the neighboring cells

40. This Cellular Cooperation Can Increase the Virulence of a Microorganism Example: Strep Infection  Scarlet Fever  Rheumatic Fever

41. The Etiology of Infectious DiseaseKoch’s Postulates • Robert Koch played an important role in determining that specific microbes were associated with specific diseases. • Four Postulates

42. 1. Same pathogen must be present in every case of the disease. 2. Pathogen must be isolated in pure culture.

43. 3. Pathogen isolated from pure culture must cause the same disease in lab animal. 4. Pathogen must be re-isolated from inoculated lab animal.

44. Exceptions to Koch’s Postulates • Inability to grow on artificial media (Syphilis)

45. Exceptions to Koch’s Postulates • Unequivocal signs and symptoms (Tetanus)

46. Exceptions to Koch’s Postulates • Diseases caused by variety of organisms (Pneumonia) • Pathogens causing variety of diseases (Streptococcus pyogenes)

47. Exceptions to Koch’s Postulates • Diseases that occur in humans only (Smallpox)

48. Classifying Infectious Diseases • Symptoms Subjective Changes Cannot Be Measured • Signs Objective Changes Measurable Changes

49. Sign or Symptom? • Pain • Temperature • Nausea • Swelling • Discomfort • Blood Pressure

50. Classifying Infectious Diseases • Syndrome A specific group of symptoms or signs that always accompany a specific disease.