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CHAPTER 1 The Background of Microbiology
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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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Introduction Microorganisms Abundant in/on the body
Many are beneficial (normal flora) Few cause disease (pathogenic) Increased ability to produce an infection (virulence) 1-4
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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
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Eukaryotes and Prokaryote
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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
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Infectious Proteins Prions Do not fit any cellular category Anucleate
Cause CNS infections Lack nucleic acid 1-7
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Eukaryotes Cell membrane Nucleus Outer layer; selectively permeable
Protects; provides passage for nutrient/waste Nucleus Control center Contains DNA (Continues) 1-8
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Eukaryotes Cytoplasm Nucleolus Ribosomes Maintains cell shape
Within the nucleus Needed for protein manufacture Ribosomes Site of protein synthesis Contain RNA (Continues) 1-9
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Eukaryotes Mitochondria Golgi apparatus Lysosomes Powerhouses
Store energy in the form of ATP Golgi apparatus Combines CHO with proteins Lysosomes Synthesized in ER 1-10
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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
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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
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Normal Flora versus Pathogens
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
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Immune System Three lines of defense Protective barriers
Circulatory or bloodstream response Innate, adaptive response Phagocyte Neutrophil Monocyte 1-14
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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
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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
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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
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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
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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
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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
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Infection
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Infection Most common disease-causing microorganisms in humans
Bacteria Viruses Fungi Parasites 1-21
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Bacteria, Virus, Fungi, Parasites
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Direct and Indirect Disease Transmission
Contact transmission Direct contact (with the person) Indirect contact (with fomite, vector, common vehicle, or airborne droplets) 1-22
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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
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Summary Classification of microorganisms Normal flora Pathogens
Prokaryotic Eukaryotic Normal flora Live on/in body Pathogens Cause disease (Continues) 1-24
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Summary Immune system response Pathogenicity Virulence Innate Adaptive
Cellular: activates phagocytes, T-cells, release cytokines Humoral: a person not previously infected, B-cells will produce antibodies Pathogenicity Ability of microbes to cause disease Virulence Strength of disease-causing microbe 1-25
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