Ch 15 – Microbiology – Flashcards
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| 5 keys to success for a pathogen |
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| -ability to contact host cells -ability to adhere to host cells and resist physical removal -ability to invade host cells -ability to complete for iron and other nutrients -ability to resist immune defenses |
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| ability to contact host cells |
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| -Helicobacter pylori swim with flagella thorugh mucous layer of stomach and adhere to epithelial cells of the mucous membranes |
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| ability to adhere to host cells and resist physical removal |
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| -pili (vibrio cholerae) -adhesins (steptococcus pyogenes) -capsules (streptococcus mutans) |
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| ability to invade host cell |
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| -invasins activate host cell's cytoskeletal machinery enabling bacterial entry into the cell by phagocytosis -Shigella |
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| ability to compete for iron and other nutrients |
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| -Neiserria |
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| ability to resist immune defense (phagocytosis and complement) |
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| -Streptococcus pneumonia is able to initially evade phagocytosis and cause infections such as pneumococcal pneumonia, sinusitis, otitis, and meningitis because of its capsule |
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| Entry of microorganisms into the host |
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| -mucous membranes -skin -parenteral route |
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| mucous membrane entry |
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| -respiratory tract as airborne particles (water droplets) -gastrointestinal tract (food, water, contaminated objects, fomites-esp. in nosocomial infections) -genitourinary tract (sexual contact) -conjunctiva (airborne particles, abrasion) |
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| examples of microorganisms that enter resp., gastro, genital, conj. |
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| -respiratory-Bordetella pertussis, influenza virus, Mycobacterium tuberculosis -gastrointestinal- Vibrio cholerae, Mumps virus, Trichinella spiralis -genital-N. gonorrhea, HIV-1, Treponema pallidum -conjuctiva-Herpes simplex virus, staphlococcus, streptococcus |
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| entry through skin |
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| -insect/animal bites, wounds, injections -Rickettsia rickettsii, Plasmodium, Rabies virus |
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| entry thorough parenteral route |
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| -tissue beneath skin or into mucous membranes -insect/animal bites, wounds, intraveinous fluids, blood transfusions, catheterization -HIV-1, HBV, Clostridium tetani |
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| adherence |
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| -attachment of microorganism to host cell mediated by adhesins -results in the production of biofilms (dental plaque) |
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| N. gonorrhea uses _____ to attach to ______ |
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| -fimbraie -receptors on cells of the genitourinary tract, eyes, and pharynx |
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| Treponema pallidum uses _____ to attach to host cells |
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| -tapered end as a hook |
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| virulence factors |
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| -toxins -capsules -cell wall components -enzymes |
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| exotoxins |
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| -proteins secreted from bacterial cell into surrounding environment -very potent-small amount are necessary to cause -solube-can diffuse into blood -produced by G+ and G- -very specific action on host -converted into toxoids, can be used as vaccine |
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| 3 types of exotoxins |
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| -A-B toxins -membrane disrupting toxins -superantigens |
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| A-B toxins |
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| -most exoxins -2 parts -active component and binding component |
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| Steps of exotoxin (Diptheria) |
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| -bacterium produces and releases exotoxins -B-component attaches to host cell receptor -A-B exotoxin enters host by endocytosis -A-B exotoxin enclosed in pinched off portion of plasma membrane of plasma membrane during pinocytosis -A-B components seperate-A alters cell function by inhibiting protein synthesis. B is released |
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| membrane disrupting toxins |
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| -cause host cells to lyse by -forming pores in plasma membrane (S. aureus) -disrupting phospholipid portion (Clostridium perfringens) -Hemolysin destroys RBCs -Leokocidins kill phagocytic leukocytes |
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| superantigens |
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| -non-specifically stimulate Th-cells to release large amount of cytokines -results in fever, nausea, vomiting, diarrhea, shock and death |
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| Endotoxins |
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| -part of G- cell wall (Lipid A) -small amount escape into surrounding fluids when ingested by phagocytes -stimulate macrophages to release high concentrations of cytokines -more general effects on host (shock, fever, diarrhea) |
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| Steps of Endotoxins |
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| -macrophage ingest G- bacteria -it is degraded in a vacuole releasing endotoxins and stimulating release of cytokines -cytokines are released into bloodstream by macrophages and travel to hypothalmus -induces production of prostaglandins which cause fever |
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| capsules |
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| -polysaccharides or polypeptides found on surface of bacteria -block attachment of phagocytic cells to bacteria -inhibit phagocytosis -Strep. pneumoniae, Haemophilus influenzae, Bacillus anthracis, Yersinia petsis |
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| cell wall components |
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| -strep. pyogenes produces M protein found on the cell surface and fimbriae -enhances attachment to host epithelial cells and protects from phagocytosis |
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| enzymes |
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| -coagulases -kinases -hyaluronidase -collagenase -IgA protease |
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| coagulases |
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| -coagulate fibringoen present in blood -fibrin clot may protect bacterium from phagocytosis -Staphlococcus |
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| kinases |
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| -break down fibrin and digest blood clots formed by body to isolate infection -s. pyogens -s. aureus |
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| hyaluronidase |
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| -digests and damages connective tissues -helps microorganism spread -s. pyogenes -c. perfringens |
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| collagenase |
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| -breaks down collagen that forms connective tissues of organs, tissues, and muscle -Clostridium |
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| IgA protease |
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| -Neisseria produces this to destroy IgA (mucosal surfaces) |
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| invasins |
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| -class of proteins that rearrange actin filaments of host cytoskeleton -enables penetration into the host cell -Salmonella and E. coli |
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| Siderophores |
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| -proteins released into the medium and take the iron away from iron-transport proteins -iron is a nutritional requirement for most pathogenic bacteria -free iron is very scare in human body -iron is mainly bound to hemoglobin, lactoferrin, transferrin, ferritin |
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| pathogenic properties of viruses |
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| -evasion of host immune defenses -cytopathic effect |
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| evasion of host immune defenses |
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| -viruses can grow inside host cells |
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| cytopathetic effect |
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| -visible effects of viral infection -may result in cell death (cytocidal) -may damage without killing |
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| cytopathic effect examples |
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| -arrest of synthesis of macromolecules (HSV stops mitosis) -release of cell's lysosomes contents -formation of inclusion bodies (nuclear and/or cytoplasmic aggregates) -formation of syncytium (fusion of adjacent infected cells) -change in the host cell's function (measles virus makes host cell produce IL-12) -production of interferons by infected cells -induction of antigenic changes on host cell -chromosomal changes in infected cell -loss of contact inhibition (unregulated growth) |
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| pathogenic properties of fungi |
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| -toxins -proteases -capsules |
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| fungi toxins |
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| -trichothecenes are fungal toxins that inhibit protein synthesis in eukaryotic cells (Fusarium and Stachybotrys) -ergot is a toxin thats grows on grain (alkaloid that causes ergotism-hallucinations (LSD)) -also constricts capillaries and prevents proper blood circulation in limbs -Aflatoxin is produced by Aspergillus flavins (grow on plants-peanuts) -Mycotoxins-phalloidin and amanitin are produced by Amanita phalloides-neurotoxins |
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| proteases |
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| -Candida albicans-produces a protease that modifies host cell membrane to allow its attachment |
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| capsules |
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| -Crytococcus neoformans produces a capsule that protects it from phagcytosis |
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| Plasmodium |
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| invade and reproduce within host cells -lysis |
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| Toxoplasma |
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| prevents normal acidification and digestion inside the phagocytic vacuoles of the macrophages it infects |
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| Giardia lamblia |
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| -attaches to the host cell and digests the cells and tissue fluids |
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| Trypanosoma and Giardia |
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| use antigenic variation |
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| exit of microorganisms from host |
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| -resp tract- talking, breathing, singing, shouting, coughing, sneezing -dead cells from skin -feces and urine -blood -milk -secretions from vagina and penis |
