Microbiology/Infectious Diseases EO 003.02

1. Microbiology/Infectious DiseasesEO 003.02

2. MAIN TEACHING POINTS • Principles of Microbiology • Bacterial Diseases • Mycoplasma, Chlmaydial, Rickettsial Diseases • Viral Diseases, Parasitic Diseases • STD/HIV/Food Bourne Diseases • Fungal Diseases/Immunocompromised Host

3. Principles of Microbiology • History of Microbiology • Role of Host and Organism • Characteristics of Microorganisms: -Bacteria -Viruses -Fungi -Rickettsia -Parasites -Mycoplasma -Chlamydia • Immunity • Prevention

4. History of Microbiology Discovery of Micro organisms Antony van Leeuwenhoek-1676 The “Father of Microbiology” • observed “little animals” • first to describe the cellular nature of living things • first to see bacteria and protozoa • but did not make the connection between the bacteria and disease

5. History of Microbiology Spontaneous Generation Disproved-Louis Pasteur-1861 • pasteurization • developed anthrax vaccine • developed rabies vaccine • introduced the terms aerobic and anaerobic in describing the growth of yeast

6. History of Microbiology:Germ Theory Role of Microbial in Disease- Joseph Lister-Surgeon-1867 • provided the first indirect evidence that microbes caused disease • postulated that microbes were a major cause of surgical infections • showed that heat sterilized instruments and carbolic acid on dogs greatly reduced post op infections.

7. History of Microbiology Role of Microbials in Disease-Robert Koch-1877 • first to demonstrate that specific microbe caused disease • established the link between Bacillus anthracis and the disease • his method of proving the cause of disease now called Koch’s Postulates Koch’s first micrographs showing Bacillus anthracis

8. History of Microbiology Microbiology in the Twentieth Century • development of sub disciplines • discovery of genetic systems in bacteria and viruses • development of chemotherapy to treat infectious diseases • molecular biology-advancement of scientific tools/equipment (electron microscopy) • gene therapy testing and genetic engineering

9. Role of Host and Organism Pathogenicity • the state of producing or the ability to produce/cause disease. Immunity • refers to the general ability of a host to resist a particular infection or disease. Virulence • refers to the ability of a bacteria to cause infection and it has two components • Invasiveness- spread • Toxigenicity- power /strength

10. Host Defenses Two Major Areas: • Non-specific resistance mechanisms • also called natural defenses • Acquired or Specific immunity • immune response

11. Nonspecific Resistance Four categories: • General-direct and indirect barriers • Physical or mechanical barriers-first line of defence • Chemical barriers • Biological-second line of defence

12. Acquired or Specific Immunity Immune Response: • Reaction of the body to foreign antigens-inflammatory response • System consisting of several immunologic mechanisms • Lymphocytes recognize and eliminate infectious agents

13. Acquired Immunity: Can be • naturally acquired or artificially acquired Can be • either active or passive

14. Acquired or Specific Immunity • Developed after exposure to an antigen or transfer of antibodies or lymphocytes from an immune donor. -naturally acquired active immunity-infection process -naturally acquired passive immunity-placental transfer -artificially acquired active immunity-vaccine -artificially acquired passive immunity-antibodies produced by animal or vitro are given to host

15. Host Defenses Specific immunity (immune response) Acquired Immunity Nonspecific Resistance General Direct/indirect Natural Artificial Physical Active Passive Active Passive Chemical Antibodies or Lymphocytes produced due to infection Antibodies are passed to fetus from placenta or colostrum Antibodies are produced as a result of immunization Antibodies produced by animal or in vitro Biological

16. Immunotherapy -Active vs passive -Drugs Variations in Host Defense Immunosuppression or deficiency -Illness -Drugs -Radiation

17. Immune Response Host Factors • Antibody-mediated immunity or humoral (AMI) • Principle immune response against extracellular bacteria -regulated by B cells and the antibodies they produce -defends against bacteria, bacterial toxins and viruses -Helper T-Cells(CD4) and macrophages identify antigen and activate cytokines ( co-stimulators of B cells) -B Cell divides into plasma cells and B memory cells - B Cells- Plasma cell produce antibodies

18. Scanning electron micrograph of human macrophage ingesting Streptococcus pyogenes. The spherical cell riding piggy-back on the macrophage is a lymphocyte, an important component in the immune response to infection.

19. 1. The macrophage eats the bacteria, 2. Proteins (antigens) from the bacteria are broken down into short peptide chains, 3. Those peptides are then "displayed" on the macrophage surface 4. Bacterial peptides are similarly processed and displayed on the surface of B lymphocytes 5. Helper T cell stimulates B Cell to turn on antibody production. 6. B Cell multiplies/enlarges and clones to be antibody secreting plasma cells, all secreting antibodies 7. Antibody binds to bacteria-enables ingestion by white cells

20. Host Factors • Cell-mediated immunity (CMI) • protective immune response against intracellular bacteria -controlled by T cells (3 types) -cells infected by viruses/bacteria in the body - trigger proliferation and differentiation of T Cells -protect against parasites, fungi, etc, can also kill cancerous body cells

21. T Cells • Three types • Migrate from red bone marrow to the thymus • Helper • CD4 T cells • Killer • CD8 T Cells • Cytotoxic • Memory • Left over from previous infection, these allow for swifter response to same antigen in the future.

22. Electron microscope picture shows a Killer T-cell (cytotoxic) about to attack a larger cancer cell

23. T-Killer lymphocyte recognizes surface markers on cells and labels them for destruction T-lymphocyte attacking and killing a much larger influenza virus. Time elasped-30min.

25. HOST FACTORS • Inflammatory response • Triggered by physical biological or chemical agents • Vasodilation of the capillaries • Permeability allowing protein rich exudate to move in to the affected area (neutrophils, macrophages) • Emigration of leukocytes into the affected area • Chemotaxis mediators released by damaged tissue draw leukocytes • Phagocytosis engulf bacterium

26. HOST FACTORS • Complement System • System of approx 20 protiens produced in liver and collectively called complement they facilitate actions of antibodies • 4 major functions • Mark an invader/antigens for phagocytosis • Target cytolysis – membrane attack complex • Supplements inflammatory response • Works with immune response

28. Organism Factors • Invasiveness • Toxigenicity • Exotoxins • Endotoxins

29. Invasiveness ability to adhere, multiply and spread • Transport to host • direct/indirect contact, vectors and fomites • Attach and colonize • requires adherence factors or adhesions • Invade the host • production of lytic substances, enzymes, or other products. • Grow and reproduce • find appropriate environment. Some very specific, eg: specific tissues or blood plasma-receptors

30. Toxigencity Exotoxins • 3 Catagories; neurotoxins, enterotoxins, and cytotoxins. • Ability to produce toxic substances • Bacterial protein (often enzymes) excreted by growing bacteria. highly toxic and often fatal • Target cell specific. Both gram + and – bacteria • Does not usually produce fever • Highly antigenic: formation of antitoxins • Botulism, tetanus, diphtheria

31. Toxigencity Endotoxins • part of cell wall of gram - • bacteria, is liberated when cell wall disintegrates. • weakly toxic and will usually produce fever, diarrhea, vomiting. • do not convert into toxoids • large doses can cause death-hemorrhagic shock and tissue necrosis • Heat stable

32. A Comparison of Endotoxins & Exotoxins Characteristic Endotoxin Exotoxin Bacterial type Gram-negative bacteria Many Gram positive bacteria, some gram negative bacteria Cellular location Lipopolysaccharide region of wall Cytoplasm (inside the cell) Chemical structure Lipid portion of the lipopolysaccharide Proteins Heat stable Stable Unstable Toxicity Low High Representative symptoms Flu-like illness, fever, inflammation, fatigue, respiratory distress, septic shock, nausea  Cell & tissue necrosis (death), neurological effects, severe dehydration Representative diseases Septic shock, humidifier disease, organic dust toxic syndrome  Botulism, cholera, diphtheria, tetanus, bubonic plague, food poisoning

33. Cells - Basic types • Procaryotic • “pro”=before,+”karyos” nucleus • lack a true nucleus • most bound by chemically complex cell wall • grow very rapidly • typical sizes: 1 um diameter • includes bacteria, viruses and archaeobacteria

34. Cells – Basic Types • Eucaryotic • “eu”=true, + “caryos”=nucleus • membrane-enclosed nucleus • complex DNA • complex processes-phagocytosis, ameboid movement • includes: protists, fungi, animals and plants • typical size: 5 micrometers (yeast cells) to 50 or 100 micrometers

35. Bacteria-characteristicsSize, Shape and Arrangement Size: • most range from 0.25 to 3. micron (µm) in diameter • 0.5 to 5 µm in length • Spirochetes can reach up to 20µm

36. Bacteria-characteristics Shape or morphology: • Coccus (sphere) • Bacillus (rod) • Spiral, spirochete (flexible corkscrew) • Vibrio (comma-shape) • Pleiomorphic (variable in shape) Pseudomonas Strep

37. Bacteria-characteristics Arrangements: • Single cell • Double cells (diplo-) • Packets of four (tetrads) • Grape-like clusters (staphylo-) • Chains (strepto-) • Single cells side to side (palisade)

38. Bacteria-characteristics • Capsule/Cell Wall -most bacteria except one group -used for identifying and classifying -made of peptidoglycan -important for identifying Gram- or Gram +

40. Bacteria-characteristics External Appendages: • Flagella-long filaments • Pili (fimbriae)-protein fibers • Conjugation or Sex pilus-hollow tubes to transfer DNA

41. Bacteria-characteristics Reproduction: • Chiefly by binary fission • Nutritional requirements • Affected by environmental factors • Short doubling time Staphylococcus aureus have gone through 2 cell divisions, producing a pair of tetrads. This can happen every 20-30min

42. LAG PHASE: Growth is slow at first  LOG PHASE: they start multiplying exponentially, doubling in number every few minutes. STATIONARY PHASE: As more and more bugs are competing for dwindling food and nutrients, booming growth stops and the number of bacteria stabilizes. DEATH PHASE: Toxic waste products build up, food is depleted and the bugs begin to die.

43. Bacteria-characteristics Survivability: • Can be destroyed by heat, light, ionizing radiation • Spores are extremely resistant to destruction • Antiseptics • Bacteriostatics • Bacteriocidals • Antibiotics Macrophage enveloping Candida albicans

44. Bacteria-characteristics Metabolic requirements: • Nutrients • Oxygen -aerobes, anaerobes • Temperature

45. Bacteria-metabolic activities Enzyme Production • Coagulases, Hemolysins-promote spread • Proteases, lipases-provide nutrients • Protective enzymes-penicillinase Toxins/gasses/pigments • Endotoxins and exotoxins can cause local or systemic effects. • Toxoids-confer immunity • Gasses-clostridia • Pigments-Pseudomonas

46. The bacterium borrelia burgdorferi is responsible for Lyme disease. Bacteria-Dissemination • Airborne • Physical contact -fomites • Secretions -universal precautions • Food/water borne -epidemics • Animals/insects -zoonoses -vectors -parasites, etc

47. Bacteria-study methods Microscopy • Dark field-unstained cells, hanging drop • Phase contrast-good for endospores or eucaryotic cells • Fluorescence-use fluorochromes, orange or green

48. Bacteria-study methods Staining: differential • Gram’s stain -divides bacteria into two classes -Gram positive-staph, strep -Gram negative-hemophilus, neisseria • Acid Fast -mycobacterium -tuberculosis -leprosy

49. Bacteria-StudyMethods • Culture -in vivo(in living body) -in vitro (outside living body, test tube) -sensitivity (C&S) Pseudomonas

50. Bacteria-Antibiotics • Systemic or topical • Bacteriocidal (kill) -penicillins, cephalosporins • Bacteriostatic (inhibit) -tetracyclines, erythromycin, sulfonamides