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45 Cards in this Set
- Front
- Back
Exotoxin
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a highly specific protein produced inside some Gram Positive Bacteria that is then secreted or released.
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Which microbes make exotoxins?
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Bacteria that produce exotoxins can be gram negative but is predominately gram positive
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What is the Function of an Exotoxin?
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The function of an Exotoxin is to poison body parts or interfere with activities in the body.
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Exotoxins work....
(3) |
-destroying certain parts of host cells
-inhibit certain metabolic functions -highly specific in body tissues |
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Exotoxins are....
(3) |
-soluble in body fluids
-can easily diffuse into the blood and are transported throughout the body. -among the most lethal substances |
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Functional types of Exotoxins (3)
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1. Cytotoxin (may also damage tissues or organs)
2. Neurotoxin (damages nerves-causes paralysis or spasms) 3.Enterotoxin (Food-poison) |
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3 Structural Types of Exotoxins
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1. A-B Exotoxins
2.Membrane-Disrupting Exotoxins 3.Superantigen Exotoxins |
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Exotoxin (4)
A-B toxins |
-consist of two parts designated A and B.
-The A part is the active (enzyme) component and the B part is the binding component. -The A-B components of the exotoxin separate. The A component alters the function of the host cell by inhibiting protein synthesis. -The B component is released from the host cell, and the receptor is inserted into the plasma membrane for reuse. |
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Exotoxins
Membrane-Disrupting Toxins |
-cause lysis of host cells by disrupting their plasma membranes.
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Exotoxins (3)
Superantigens |
-Bacterial proteins; antigens that provoke a very intense immune response.
-stimulates the proliferation of immune cells called T-cells. These cells are types of white blood cells (lymphocytes). -In response to superantigens, T-cells are stimulated to release enormous amounts of chemicals called cytokines. |
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Exotoxins- Superantigens
Cytokines |
-small protein molecules produced by various body cells, especially T Cells, that regulate immune responses.
-excessively high levels of cytokines released by T cells enter the blood stream and give rise to a number of symptoms including fever, nausea, vomiting, diarrhea, and sometimes shock and even death. |
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ANTITOXINS
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The body produces antibodies that provide immunity to exotoxins.
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TOXOID
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The denatured or inactivated Exotoxin which is useful as a vaccine to induce immunity and stimulate antibody production.
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BOTULINUM EXOTOXIN
common clinical form: |
Clostridium botulinum (botox)
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BOTULINUM EXOTOXIN
How many types exist? |
7 types of Exotoxins: A-G
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BOTULINUM EXOTOXIN
lethal doses: |
A lethal dose of 135-150ng of Botox is considered fatal
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Which Botulinum Exotoxin type has cosmetic value?
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-Type-A (the deadliest of all 7 types)
-A cosmetic dose of BOTOX® is just about 20 - 50 units |
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ENDOTOXINS
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-part of the outer portion of the cell wall of gram negative bacteria
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Gram-negative bacteria...
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-have an outer membrane surrounding the peptidoglycan layer of the cell wall.
-the outer membrane consists of lipoproteins, phospholipids, & lipopolysaccharides (LPS). -LPS aka Lipid A is the endotoxin |
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How do endotoxins work? (2)
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-Endotoxins are released when gram-negative bacteria die and their cells undergo lysis resulting in releasing the endotoxin.
-Endotoxins are also released during bacterial multiplication. |
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How does the use of antibiotics affect endotoxins?
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-Antibiotics used to treat diseases caused by gram-negative bacteria can lyse the bacterial cells.
-This reaction releases endotoxin and may lead to an immediate worsening of symptoms. |
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What are the symptoms of endotoxins? (2)
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-endotoxins exert their effects by stimulating macrophages to release cytokines in very high concentrations. At these levels cytokines are toxic.
-all endotoxins show the same symptoms: chills, fever, weakness, generalized aches, and in some cases shock and even death. |
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Shock
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-refers to any life threatening decrease in blood pressure.
-shock caused by a bacteria is called septic shock. -Gram-negative bacteria cause endotoxic shock. |
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List characteristics of Microbial Life (8)
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1. Irritability-Respond to the Environment
2. Movement 3. Nutrition-Eat & Consume Food 4. Metabolism- Process Food 5. Respiration-Breath 6. Excretion-Get rid of Metabolic wastes 7. Growth-Grow & Develop 8. Reproduction-Reproduce "...their kind" |
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Minimum Conditions
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the lowest condition or amount microbes need to initiate development; growth may not occur below this point.
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Optimum Conditions
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most favorable condition or amount for organism.
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Maximum Conditions
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highest condition or quantity microbes can endure; beyond this, growth is impaired & microbial death may occur.
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What is the purpose of Respiration?
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-an ATP generating process
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Positive Stimuli
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attract living things because they indicate environments that support life and promote growth, or stimulate development.
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Negative Stimuli
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repel because they signal danger or environments that could impede life and inhibit microbial growth or development.
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Requirements for growth
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-divided into two main categories: physical & chemical.
-physical aspects include temperature, pH, & osmotic pressure. -chemical requirements include sources from carbon, nitrogen, sulfur, phosphorus, oxygen, trace elements, and organic growth factors. |
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Describe a capsule (4)
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-glycocalyx (sugar coat) is a substance secreted by prokaryotes
-its sticky and is external to the cell wall and composed of polysaccharide, polypeptide, or both. -If the substance is organized and is firmly attached to the cell wall, the glycocalyx is described as a capsule. -If the substance is unorganized and only loosely attched to the cell wall, the glycocalyx is described as a slime layer |
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What is a capsule made of?
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-composed of polysaccharide, polypeptide, or both.
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What is a capsule's function?
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-capsules are important in contributing to bacterial virulence (the degree to which a pathogen causes disease)
-capsule often protect pathegenic bacteria from phagocytosis by the cells of the host. |
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What groups of dyes are used for Capsule staining?
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-Flurochrome & Immuno-fluorescence microscopy
-Negative staining -Nigrosin dye |
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Fimbraie (4)
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-are numerous short hair-like appendages of Gram-negative bacteria.
-occur at the poles of the bacterial cell or can be evenly distributed over the entire surface of the cell -can number anywhere from a few to several hundred per cell. -has a tendency to adhere to each other and to the surface. |
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What does fimbraie do for bacteria?
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-can help bacteria adhere to epithelial surfaces in the body
-once colonization occurs, the bacteria can cause disease. |
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Pili
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-usually longer than fimbraie and number only one or two per cell.
-involved in motility and DNA transfer |
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What does pili do for bacteria?
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Bacteria specifically use the Pilus to attach to other bacteria, forming a tube through which genetic material can be transferred between cells (Conjugation (sex) pili)
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Mycolic Acid
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-the acid-fast stain is used to identify all bacteria of the genus Mycobacterium and pathogenic species of Nocardia.
-these bacteria contain high concentrations (60%) of a hydrophobic waxy lipid in their cell walls that prevent the uptakes of dyes -the mycolic acid forms a layer outside of a thin layer of peptidoglycan |
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Staining Mycolic Acid bacteria
Dyes |
1. carbol fuchsin
2. counter stain- methylene blue |
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What is an endospore?
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-A special resistant, dormant structure formed within a cell that protects a bacterium from adverse environmental conditions.
-formed by few genera like bacillus and clostridium |
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Sizes of Endospores
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-Bacillus- generally produce normal or under-sized endospores. Therefore, the cells look regular with no bulge.
-Clostridium-oversized spores tend to be over-sized. Therefore, the cells appear swollen to accommodate the endospores |
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Location of Endospores
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1. Central- are exactly in the middle and may be smaller, bigger, or same size as the cell.
2. Subterminal -occur anywhere between the middle and end of the cell and may be smaller, bigger, or same size as the cell. 3. Terminal- are at either end of the cell and may be smaller, bigger, or same size as the cell. |
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Tetanus
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A Gram Positive bacterium with an over-sized, terminal, endospore that makes it look like a drumstick is typical of the disease agent for
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