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1-1. CHAPTER 1 The Background of Microbiology. 1-2. Introduction . Microbiology: study of organisms that cannot be seen by gross examination Microscope is needed Three types of microscopes Basic compound microscope Scanning electron microscope Confocal laser microscope (Continues). 1-3.

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  1. 1-1

  2. CHAPTER 1The Background of Microbiology 1-2

  3. Introduction Microbiology: study of organisms that cannot be seen by gross examination Microscope is needed Three types of microscopes Basic compound microscope Scanning electron microscope Confocal laser microscope (Continues) 1-3

  4. Microorganisms Abundant in/on the body Many are beneficial (normal flora) Few cause disease (pathogenic) Increased ability to produce an infection (virulence) Introduction 1-4

  5. Classifications of Microorganisms According to cell type Protists (one-celled organisms) Two groups Prokaryotes (e.g., bacteria, mycoplasmas) Eukaryotes (e.g., animals, plants) (Continues) 1-5

  6. Classifications of Microorganisms Unclassified microorganisms include Viruses Incapable of reproducing on their own Require a host cell For example, measles, HIV, common cold 1-6

  7. Infectious Proteins Prions Do not fit any cellular category Anucleate Cause CNS infections Lack nucleic acid 1-7

  8. Eukaryotes Cell membrane Outer layer; selectively permeable Protects; provides passage for nutrient/waste Nucleus Control center Contains DNA (Continues) 1-8

  9. Eukaryotes • Cytoplasm • Maintains cell shape • Nucleolus • Within the nucleus • Needed for protein manufacture • Ribosomes • Site of protein synthesis • Contain RNA (Continues) 1-9

  10. Eukaryotes Mitochondria Powerhouses Store energy in the form of ATP Golgi apparatus Combines CHO with proteins Lysosomes Synthesized in ER 1-10

  11. Prokaryotes • Contain • Cell membrane, cell wall • No nucleus (anucleate) • Nucleoid for storing DNA • Capsule of slime layer to increase resistance to antibacterial agents (Continues) 1-11

  12. Prokaryotes Cilia (short, fine filaments that move fluid over a surface) Flagella (long filaments that provide motility for the cell) Spores (hard outer wall produced by inactive bacterial cells) 1-12

  13. Normal Flora versus Pathogens • Normal flora • Exist on, in, or around us; may become pathogenic if they do not remain in intended location of the body • Most prevalent in areas open to the outside • Not found in blood or CSF • Pathogen • Capable of causing disease 1-13

  14. Immune System • Three lines of defense • Protective barriers • Circulatory or bloodstream response • Innate, adaptive response 1-14

  15. Protective Barriers Intact skin and its secretions Respiratory tract (e.g., mucus, sneezing) GI tract (e.g., saliva, acidic pH of stomach) GU tract (e.g., expulsion of urine) 1-15

  16. Circulatory and Bloodstream Response • Phagocytes (phag/o = to eat) • Neutrophils, monocytes, macrophages, dendritic cells • Lysosomes • May be in fixed locations (e.g., bone marrow, liver) or may roam to location of foreign substance 1-16

  17. Innate Immune Response • Exists at birth • Is not pathogen specific • Does not require previous exposure • Kills invading microbes • Begins inflammatory response (redness, swelling, and pain) • Alerts adaptive immune response 1-17

  18. Innate/Adaptive Immune Response • Antigen presenting cells (APCs) • Macrophages and dendritic cells kill microbes • Present intruding microorganisms to T cells • Antigen • Marker recognized as foreign • Phagocytic cells engulf pathogen, presenting fragments on its surface, notifying the adaptive immune system of invader 1-18

  19. Adaptive Immune Response • Cellular mediated • Recognizes pathogen • Activates T cells (which secrete cytokines) • Humoral response • T cells interact with B cells that produce antibodies (immunoglobulins) • Antibodies destroy antigen 1-19

  20. Infection • Caused by invasion by microbe • Localized or generalized • Virulence determined by • Cell structure • Production of endotoxin (contained within the microbe) or exotoxin (produced by and secreted by the microbe) (Continues) 1-20

  21. Infection • Most common disease-causing microorganisms in humans • Bacteria • Viruses • Fungi • Parasites 1-21

  22. Direct and Indirect Disease Transmission • Contact transmission • Direct contact (with the person) • Indirect contact (with fomite, vector, common vehicle, or airborne droplets) 1-22

  23. Fever and the Inflammatory Response • Infection accompanied by • Fever • Assists in clearing infections • Important defense mechanism • Inflammation • Part of the innate immune response • Caused by dilatation of blood vessels • Infiltration of infected site by antibodies and WBCs results in death of the microbe 1-23

  24. Summary • Classification of microorganisms • Prokaryotic • Eukaryotic • Normal flora • Live on/in body • Pathogens • Cause disease (Continues) 1-24

  25. Summary • Immune system response • Innate • Adaptive • Cellular • Humoral • Pathogenicity • Ability of microbes to cause disease • Virulence • Strength of disease-causing microbe 1-25

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