Pathogenicity Test Questions – Flashcards
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| intermediate host |
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| serves as a temporary but essential enviroment for some stages of parasites development |
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| transfer host |
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| is not necessary for development but serves as a vehicle to the final host |
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| reservior host |
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| nonhuman organism infected with a parasite that can also infect humans |
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| infection |
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| growth and multiplication of parasite on or within host |
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| infectious disease |
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| disease resulting from infection |
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| pathogen |
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| a parasite organism that causes infectious disease |
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| pathogenicity |
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| the ability for a pathogen to cause disease |
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| the outcome of a host-pathogen relationship depends on |
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| the number of pathogen organisms present virulence of pathogen host's defense or degree or resistance |
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| virulence |
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| measures the degree or intensity of pathogenicity |
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| 3 things virulence depends on |
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| 1. infectivity- the ability to establish a focal poitn of infection 2. invasivness- abuility to spread to adjecent cells or other tissue 3. pathogenic potential - the degree to which pathogens can cause damage to host the major aspect is toxgenicity ( the ability to prodeuce toxins) |
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| lethal dose 50 (LD50) |
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| the number of pathogens that will kill 50% of an experimental group of hosts |
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| infectious dose 50 (ID50) |
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| number of pathogens that will infect 50% of an experimental group of host |
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| a successful basterial pathogen must be 7 things |
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| 1. maintain a reservior - place to live before and after infection 2. be transported to host 3. adhere to, coloinze, and or/ invade host 4. multiply or complete life cycle on or in hsot 5. initially evade host defenses 6. damage host 7. leave host ( return to reservior or enter new host |
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| all bacterial pathogens must have at least one reservior? |
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| true |
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| for human pathogens what are three reserviors |
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| other humans animals enviroment |
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| what are two types of contact between hosts |
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| direct contact- coughing, sneezing, body contact indirect contact- vehicles ( soil, air, water,food), vectors ( living organisms that transmit pathogens), fomites ( inanimate objects that harbor and tranmit pathogens) |
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| attachment of a parasite to a host is mediated by special molecules or structures called |
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| adhesins or ligands which help bind to the receptors of the host cells |
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| common adhesins or ligands that help the parasite bind to the receptors of the host are |
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| fimbriae or pili, glycocalyx or capsule, slime layer, M protein, techoic and liotechoic acids |
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| what is colonization |
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| establishment of a site of microbial reproduction on or within host |
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| colonization depends on |
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| ability of the pathogen to compete |
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| is the result of colonization necessarily tissue invasion and or damage? |
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| no |
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| what can the invasion of the bacterial pathogen be |
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| can be active penetration of hosts mucous membrane or epithelium via lytic substance that alter host tissue |
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| in what three steps does the invasion os a bacterial pathogen accomplish penetration |
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| 1. attack the ground substance and basement membranes of integuments and intestinial lining 2. degrade protein-carbohydrate complexes between cells 3. disrupt the cell surface |
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| passive penetration of invasion of the bacterial pathogen can be |
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| skin or mucous lesions, insect bites, damage by other organism, wounds or abrasions, phagocytosis, endocytosis |
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| once below mucous membrane bacterium can spread into deeper tissue |
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| true |
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| when bacterium spreads into deeper tissue what might result |
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| may involve production or specific products and or enzymes that promote spreading may enter small terminal lymphatic capillaries once the circulatory system is reached the pathogen has access throughout the host. |
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| when does the pathogen have access throughout the host? |
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| once the pathogen has reached the circulatory system |
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| when does growth and multiplication of the pathogen occur |
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| once the pathogen finds the appropriate enviroment within the host |
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| do some pathogens actively grow in the blood plasma? |
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| yes |
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| bacteremia |
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| presences of viable bacteria in blood |
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| septicemia |
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| presence of bacteria or of their toxins in the bloodstream |
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| the pathogen must leave the cell is it is going to be perpetuated |
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| true |
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| the pathogen leaves the hoat and either moves to -- or to -- |
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| another host or into a reservior |
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| most pathogenic bacteria leave by passive mechanisms for example |
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| feces, droplets, saliva,desquamated cells |
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| virulence factors |
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| products or structural components that contribute to virulence or pathogenicity |
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| example of virulence factors |
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| adhesins, capsules, lytic subastances, products promoting spread |
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| often enviromental factors control expression of virulence factors |
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| true |
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| 3 examples of regulation of virulence factors which are coontroled often by enviromental factors |
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| 1. gene for diptheria toxin regulated by iron 2. expression of virulence genes increased by body temperature 3. expression of cholera toxin regulated by PH, temperature osmolarity and available amino acids |
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| intoxications |
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| disease that results from entry of a specific preformed toxin into host |
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| toxin |
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| a substance that alters the normal metabolism of host cells with negative effects on the host |
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| towins of bacteria are two types |
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| exotoxins and endotoxins |
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| exotoxins |
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| soluble, heat liable proteins that are usually released into the surrounding as the bacteria grow |
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| endotoxins |
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| the LPS of the gram negative bacteria |
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| exotoxins are specialized by specific bacteria ( often with plasmid or prophage containing toxic genes) |
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| yes |
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| are exotixins heat liable proteins which are inactivated at 60-80 degrees celcius? |
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| yes |
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| what are among the most lethal substances known |
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| exotins |
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| exotoxins are not associated with a specific disease and have no specific mechanism of action |
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| false they are associated with a specific disease and have a specific mechanism of action |
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| highly immunogenic ( antitoxin antibodies are formed for endotoxins or exotoxins? |
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| exotoxins |
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| are endotoxons or exotoxins easily inactivated by chemicals? |
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| exotoxins, |
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| formaldehyde and iodine form immunogenic toxiod are examples of chemicals which inactivate endo or exo toxins? |
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| exotoxins |
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| AB exotoxins are composed of two subunits |
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| A subunit- responsible for toxic affect B subunit - binds to the target cell |
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| examples of AB exotoxins entry |
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| diptheria toxin |
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| can AB toxins be specific host site exotoxins? |
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| yes |
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| spcific host site exotoxins may include |
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| neurotoxins enterotoxins cytotoxins AB toxins |
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| neurotoxins |
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| usually ingested as preformed toxins target nerve tissue |
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| enterotoxins |
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| target intestinal mucosa elicit profuse fluid secretion |
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| cytotoxins |
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| specific toxic action on cells/tissues of specific organs |
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| membrane disrupting exotoxins |
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| lyses the cell by disrupting the integrity of the membrane they produce pore forming exotoxins which bind to the cholesterol portion of the membrane and insert itself in the membrane |
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| phospholipases are a type of --- that do what --- |
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| are a type of membrane disrupting exotoxins that remove charged heads of phospholipids and destabilizes the membrane |
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| leukocidins |
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| a type of pore forming exotoxin that kills phagocytic leukocytes |
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| hemolysins |
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| are a type of pore-forming exotoxin that kills erythrocytes, leukocytes and many other cells |
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| streptolysin O |
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| a type of hemolysin that is oxygen sensative |
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| streptolysin S |
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| a type of hemolysin that is oxygen stable |
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| superantigens |
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| nonspecifically stimulate T-cells, and cause a massive release of cytokines |
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| what do superantigens result in |
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| systematic toxicity in host and supression of specific immune response |
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| what are two prime examples of superanitgens |
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| 1. staphylococcal enterotoxins that cause food poisioning and the toxin that causes toxic shock syndrome |
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| with endotoxins what is the toxic portion of the LPS |
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| the lipid A, not a singel macromolecular structure seems to be a complex array of lipid residues |
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| is endotoxins heat stable |
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| yes |
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| when are endotoxins toxic? |
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| only at high doses |
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| are endotoxins highlt immunogenic? |
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| no weakly |
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| endotoxins are usually capable of producing general systematic effect like |
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| fever shock blood coagulation weakness diarea inflamation intestinal hemmorage fibrinolysis |
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| endotoxins bring about effect indirectly by interacting with host molecules and cell activating host systems |
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| true |
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| when endotoxins interact with macrophages they release |
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| endogenous pyrogen |
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| when endotoxins bind to the LPS binding protein they release |
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| cytokines |
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| exotoxins are ---- whereas endotoxins are |
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| proteins.. lipopolysaccharides |
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| endotoxins are released when |
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| gram-negative bacteria die and their cell walls undergoe lysis |
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| what three things on the envasion of a bacteria help the bacteria stay away from the comliment system |
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| capsules, lengthened O-chanin, serum restance |
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| what is serum resistance |
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| modifies lipoolingosacharides interfere with formation of membrane attack system |
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| what is the compliment system |
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| The complement system helps or “complements” the ability of antibodies and phagocytic cells to clear pathogens from an organism |
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| what helps bacteria resist phagosytosis of the host cell |
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| 1.capsules 2.specialized surface proteins -that block adherence of phagocyctes of bacterium 3.production of leukocidins 4. proteases production- that cleave compliment factor C5a (phagocyte chemoattractant) |
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| how do bacteria pathognes survive inside phagocytic cells? |
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| escape from phagosome before fusion with lysosome prevents fusion of lysosome with phagosome resistance to toxic products of phagolysosome |
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| how do bacteria pathogens invade the immune responce |
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| capsules, genetic variation of surface antigens production of IgA proteases production of proteins that interfere with antibody-mediated opsonization ( the process of targeting an antigen) |
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| exotoxins are ---- whereas endotoxins are |
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| proteins.. lipopolysaccharides |
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