Flashcards
Host Defenses and Pathogenicity
Cards in this deck (28)
- 1Time for ingested organismThere is a given set amount of hours that it has available to it to attach to somewhere in the intestines and replicate before it will be shot out of the intestines. Time is limited while trying to find targeted binding site to colonize
- 2Path of microbe in human host1. Mouth (Enzymes, antibodies)
2. Esophagus
3. Stomach - acidic at 1.8 pH
4. duodenum - dumping to gall bladder
5. Gall bladder (bile - antimicrobial)
6. pancreas (enzymes - protein structures degraded)
7. small intestine (microflora)
8. large intestine (competition with large # in microflora) - 3Host Defense1. Physcial barriers
2. Mouth - lysozyme, antibodies IgA
3. Peristalsis
4. Stomach - HCl, pH <2, pepsin
5. Small, large intestine - digestive enzymes, bile, resident microflora, mucus layer
6. Innate, adaptive immunity - 4Battle ground1. Intestinal tract: intestinal villi in lumen, increases SA and absorbance of nutrients
2. Mucin covers villi, covered by bacteria - 5Villi1. Small intestine
2. Lacteal: lymph draining system
3. Goblet cells: produce mucin
4. Crypt: some pathogen will seek out crypts to colonize (Camplyobacter) - 6Immune System1. Innate immunity: includes phagocytes, antimicrobial peptides
2. Adaptive: includes B and T cells (B ad T lymphocytes) - 7Cell Mediated (innate) ImmunityPhagocytosis is central
Use of phagocytes and T cells (lymphocytes) - 8Phagocytosis1. Receptors identify foreign particles
2. phagosome formed on interior of phagocytic cell, fuses with lysosome
3. destroyed+dumped to environment (exocytosis)
Lysosome contains: proteases, lipases, carbohydrases, lysozyme; hydrogen peroxide, free radicals such as superoxide anion, singlet oxygen, hydroxyl radical - 9Humoral Immunity: Antibody-mediated response (Adaptive)1. B cells are primed with specific antigens on virus or microbe
2. Triggers production of antibodies - 10Gut-associated Lymphoid Tissue1. Lamina propria - rich in B cells, T cells, macrophages
2. Peyer's patches (lacteal) - B, T cells, macrophages, M cells
3. Mesenteric lymph nodes - collection points for lymph that drains from intestinal vili and Peyer's patch - 11M cells1. Extensions that reach out into lymph and grab foreign particle
2. Transfer unmodified antigen across cell to underline immune system
3. Present to B cells, helper T cells
4. Exploited by salmonella
5. Entry point where B cells are constantly primed - 12Immune system attacking self: Chronic maladies associated with diarrhea1. Arthritis, kidney damae, neurological damage (myelin sheath)
2. Arthritis with Camplyobacter, Salmonella, Shigella, Yersinia
3. Associated with HLA-B27 antigen
4. Gullain-Barre Syndrome - C. jejuni - 13Allergies1. disorder of immune system
2. Histamine - 14Increases Risk1. antibiotics
2. Antacids
3. Large volume of water
4. Fatty foods
5. nutritional deficiencies
6. Poor hygiene - 15Virulencedegree of pathogenicity of a microbe, or the relative ability of a microbe to cause disease. The word virulent, which is the adjective for virulence, is derived from the Latin word virulentus, which means “poisonous”
- 16General characteristics of infectious organisms1. viable in vivo
2. Pass low pH in stomach,
3. Compete with microflora for docking sites, target tissues, and nutrients
4. Can multiply within GI tract
5. Can penetrate mucosal barier if need to to reach its target site
6. Overcome host defense - 17Function of Virulence factors1. Attachment
2. Invasion
3. Evasion - block phagocytosis, produce proteases to destroy antibodies
4. Essential nutrient, iron
5. Toxins
6. Secretion systems - 18Attachment1. Adhesins that bind to specific receptors on host cells
2. Fimbrial adhesins - outer membrane proteins or secreted proteins (curli -
E. coli, Samonella, filamentous hemagglutinin adhesin)
3. Pathogens may adhere to extracellular matrix such as collagen, fibronectin, IgG - 19Pili1. Type I pili: present in many members of Enterobacteriaceae
2. P pili: specific adherence of uropathogenic E. coli to uroepithelial cells - 20Survival inside phagocytes1. Enzymes degrade membrane-bound vacuole
2. Prevent acidification of phagosome and fusion with lysosome
3. Neutralize reactive oxygen species (superoxide dismutase)
4. Proteases degrade host lysosomal proteins
5. Capsules - phagocytes can't phagocytize
6. Microbes may also induce endocytosis in non-phagocytes - 21Evasion1. Ig proteases - breakdown antibodies
2. Polysaccharide capsules - inhibit phagocytosis
3. Bind host proteins to make look like self
4. Antigenic variation of surface components - 22Nutrient Acqusition1. Iron is tightly bound by high-affinity proteins in host
2. Bacteria will bind to these proteins or produce siderophores that bind iron b/c iron regulates virulence genes (high [iron], genes turned on) - 23Cytotoxicity1. IpaB produced by Shigella flexneri kills macrophages
2. Some toxins cause tissue damage and induce host responses (diarrhea) - 24Bacterial toxinsTarget membranes, ribosomes, secondary signal pathways (hormones)
- 25Why do bacteria retain toxin1. Dissemination
2. Nutrients
3. Reduce competitors
4. Unknown function - 26Secretion SystemsTransport cytoplasmic proteins to cell wall, outer membrane, or surrounding environment
1. General: signal peptides, used by gram (-)
2. 6 pathways in gram (-)
3. Type III secretion system - trigger y contact with host cell, looks like syringe - 27Regulation of virulence factors1. Tightly regulated
2. Expression linked to environmental signals (temp, oxygen, CO2, iron, pH, osmolarity, nutrients)
3. Global regulators - 28Pathogenicity Islands1. Often contain multiple virulence genes
2. G+C content of island differs from host genome
3. Island flanked by direct repeats, tRNA genes, insertion sequence elements
4. Integrase, transposase, origin of replication is present
5. On chromosome or plasmid
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- Food Microbiology (Exam 2) Flashcards on Host Defenses and Pathogenicity, created by Amanda Vang on 11/11/2017.
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- Amanda Vang
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