Lecture 301. Know the examples of enzyme virulence factors discussed in class and how they contribute to virulence a. Hyaluronidase- breaks down hyaluronic acid polymer that glues host cells togetherb. Collegenase- breaks down collagen in connective tissuec. Streptokinase- destroys fibrin of blood clotsd. Coagulase- Found on the exterior of pathogenic staphylococcus aureus cells- creates a fibrin layer around the cell that prevents immune system from detecting the bacteria2. Contrast bacteremia and septicemia a. Bacteremia- when bacteria are in the circulating bloodi. Pathogens can easily be transported to other tissues and organsb. Septicemisa-In some cases, a systemic inflammatory response occirs because of bacteria in the blood or lymph system, leading to life-threatening sepsis.3. Know what virulence, virulence factors, and virulence genes are a. Virulence factors- Disrupt connective tissues or destroy host cellsb. Virulence factor- A pathogen-produced substance (usually a protein, enzyme, adherence factor, or toxin) that promotes the establishment and pathogenesis of an infectious diseasec. Virulence genes- encode for virulence factors4. Understand how to quantify virulence (Lec. 29) a. LOOK AT LECTURE 295. Compare the differences between endo, exo, and enterotoxins a. Endotoxins- lipopolysaccaries of gram negative bacteria that are released into surrounding tissues after lysis of the cellb. Exotoxins- proteins that are excreted by bacteria and are toxic to host cellsc. Enterotoxins- exotoxins that affect the small intestine6. Understand about the function of each of cytolytic toxins, AB toxins, and superantigensa. Cytotixins- cause damage to host cell membranes; can cause host cell lysis and deathb. AB toxins- Consist of two subunits; B subunit binds to surface to specific host cells and A subunit enters host cell where it acts as an enzyme to produce host and cell damagec. Superantigens- Proteins that cause a hyper-stimulated immune response resulting in excessive inflammation and tissue damage7. Know the pathogens and mechanisms of action of diphtheria, tetanus, botulism, cholera,a. Diphtheriai. Is an AB toxin that kills host cells by blocking protein translation ii. Produced by corynebacterium diptheriae (produces an AB toxin)iii. 1. B fragment binds to host cell receptorsiv. 2. A fragment enters cell and blocks tRNA from entering the ribosome by catalyzing modification of elongation factor1. ADP ribose is attached to elongation factor 2 and protein synthesis is prevented (ADP-ribosylation)b. Tetanusi. AB toxins that block neurotransmitter release from nerve cells that signal musclesii. Produced by species of the spore-forming anaerobe Clostridium, normally found in soilsiii. Bacterium colonizes and grows in deep anoxic woundsiv. Exotoxin spreads throughout body toxin binds to inhibitory interneurons. Preventing their function spastic paralysis (muscles constantly stimulated to contract)c. Botulismi. Produced by C. botulismii. 7 typesiii. type A had medical uses- migraines & sweating, muscle spasmsiv. Usually results from improper food preservation, where bacterium grows and produces toxinv. Toxin spreads throughout the body, eventually affecting many muscles – results in flaccid paralysisd. Cholerai. Caused by Vibrio choleraii. Bacterium colonizes small intestine wall and produces chorlea toxiniii. An AB toxin that binds to intestinal epithelial cells1. The A fragment enters host cell and acts as an enzyme to stimulate formation of cyclic AMP2. Increased cyclic AMP alters regulation of ion movement across the epithelium increased ion concentration in SI osmosis, fluid loss, diarrhea8. Describe medical uses of Type A botulism toxin a. Migraines, sweating, muscles spasms9. Know the symptoms caused by endotoxins and understand the tests used to detect them a. Effects of endotoxins on humans and animals i. Fever: endotoxin stimulates the host to release endogenous pyrogens which regulate temperatureii. Diarrheaiii. Inflammationiv. Are generally less toxic than exotoxins b. Assays for endotoxins- Pharmaceitical solution may be sterile, but still contain fragments of dead bacteria and endotoxins. There must be a way to assay for endotoxins which may be in the solutioni. Limilus amoebocyte assay (LAL) – many kinds of color generating or fluorescence- generating detection kits are based in LALii. Blood cells of Limulus are extremely sensitive to endotoxins, which cause the cells to lyse 10. Describe examples of innate resistance a. Definition- IS protection from pathogens that does not rely on previous exposure to the pathogeni. Physical barriersii. Chemical Barriersiii. Normal microflora11. Define a compromised host and an immunocompromised host a. Compromised Host- One in which mechanisms of resisting pathogens is weakened by: injury, illness from a pathogen or from another disease.b. Immunocompromised host- A weakened immune
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