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110 Cards in this Set
- Front
- Back
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Epidemiology
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The study of when and where diseases occur and how they are transmitted in populations
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Epidemiology
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Occurrence, distribution, and determinants of health and disease in a population centers
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Centers for Disease Control
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- most epidemiology of infectious disease
- e.g. E. coli O157, Ebola, swine flu, etc. |
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Symptoms, signs
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Each disease shows certain subjective ______ and objective _____
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Syndrome
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If symptoms always accompany the disease
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Acute
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- rapid and short-lived
- may be lethal (Ebola) - often "newer" pathogen host lacks resistance to |
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Chronic
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- develops slowly
- can be less severe - well-adapted pathogens cause less harm - e.g. Hepatitis B and TB |
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Latent
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- inactive for given time
- later, activated - e.g. Shingles |
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Local
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Limited to a small area of the body
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Systemic
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Microbes spread throughout the body
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Focal
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Local infection that spreads to other specific regions
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Primary infection
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Initial acute infection
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secondary
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after primary weakens immune response ; usually opportunistic
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subclinical
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does not cause noticable disease, but is carried by individual
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predisposing factors
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- makes people more or less susceptible
- AKA risk factors |
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predisposing factors
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genetics (sickle-cell, resistance to malaria), age, nutrition, stress, preexisting illnesses are examples of what?
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infection period
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the organism invades, colonizes, and grows in the host
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predisposing factors
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females higher incidence of UTIs is an example of what?
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incubation period
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- time between infection and visible symptoms
- depends on hosts health - virulence of pathogen |
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prodromal period
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- short
- post-incubation - mild symptoms |
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period of illness
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- AKA acute disease stage
- strong symptoms |
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period of decline
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- overcome illness
- symptoms subside |
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convalescence
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body starts to return to pre-disease state/return to normal
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incidence
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- # of new cases in a given time
- people who develop disease |
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prevalence
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total # of new and existing cases at a given time
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sporadic disease
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- occurs occasionally
- e.g. Cholera in US |
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endemic disease
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- always present in population
- usually at a low level - e.g. malaria in tropics and common cold in the US |
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epidemic
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- infects many people in a given area for a short period of time
- e.g. influenza |
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pandemic
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- epidemic that occurs worldwide
- e.g. really bad influenza strain |
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communicable
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- indirectly spread from host to host
- e.g. chicken pox, measles, herpes, etc. |
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contagious
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- easily spread from one host to another
- e.g. chicken pox |
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noncommunicable
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- not spread from host to host
- e.g. tetanus |
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direct host-to-host
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transmission via touching. sexual intercourse, kissing
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indirect contact
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- transmit pathogens via fomite
- e.g. door knob, towels, utensils, etc |
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droplet
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transmit via coughing, sneezing
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vehicle
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- transmit pathogen by a medium
- e.g. waterborne (Cholera), foodborne (Salmonella), airborne (respiratory pathogen), blood, etc. |
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reservoir
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- source of disease
- e.g. human (typhoid Mary), animal (zoonosis), protozoa (amoeba), nonliving (contaminated water, soil) |
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vectors
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- living organisms/animals (often arthropods) that carry pathogen to host
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mechanical
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- type of vector
- on insect body part; gets on host food |
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biological
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- type of vector
- usually need bite or other blood exchange - e.g. deer tick |
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nosocomial infections
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- hospital acquired
- e.g. Staphylococcus aureus, Enterococcus sp., Clostridium difficile |
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emerging infectious disease (EID)
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- "newer" diseases of increased incidence caused by microbes
- e.g. swine flu, bird flu, Ebola, HIV, West Nile |
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re-emerging disease
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- diseases that were under control that are again a major health problem
- e.g. TB, MRSA, Malaria |
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pathogenicity
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the ability to cause disease by overcoming the defenses of a host
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virulence
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- the relative degree or extent to which a microbe can cause disease
- can quantitate |
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virulence factor
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a trait/factor that contributes to the ability of a pathogen to cause disease
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species, strain, and host
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virulence can vary by what factors?
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dynamic
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disease is what kind of process?
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gene expression
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what is essential to invading the host?
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mucous membranes
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- many pathogens
- respiratory or GI tract - e.g. colds/flu, food poisoning, UTIs/STDs |
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- mucous membranes
- skin - parenteral portal - preferred portal |
what are the portals of entry into the host?
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skin
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generally impenetrable, unless broken/lesion
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parenteral route
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- direct deposit of microbes into tissues beneath skin or mucous membrane
- due to injury - e.g. HIV, hepatitis, rabies, Clostridium tetani |
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preferred portal
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- may have > or = 1 that lead to disease
- one: influenza virus - multiple: Yersinia pestis (bubonic or pneumonic plague) |
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infectious dose
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# of units/cells required to cause disease
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ID50
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- infectious dose for 50% of a sample population
- e.g. Bacillus anthracis |
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lethal dose
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often used for potency of toxin (ID50)
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botulinum toxin
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ID50 for botulinum toxin is 0.03ng/kg in mice, vs. 250 ng/kg for Shiva toxin
- which is more lethal/potent? |
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virulence factors that contribute to disease
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- adhering to host cells to gain entry
- penetrating host defenses - taking nutrients from host - direct physical damage - toxin production - genetic recombination leading to increase virulence |
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adherence
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attachment of non-pathogens to host cells or tissues at the portal of entry
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adherins (ligands)
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- molecules on pathogens surface that bind specifically to complementary receptors on a particular host cells
- most are glycoproteins, lipoproteins - e.g. Streptococcus mutans-dental caries |
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biofilms
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- surface-attached communities
- catheters, plague, etc |
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avirolent
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- species w/o capsules can be this
- unable to cause disease |
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S. pneumoniae
B. anthracis Y. pestis |
capsules are a virulence factor for what?
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cell wall
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M protein on cell surface aids attachment, resists phagocytosis
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exoenzymes
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- extracellular
- digest host fibers/cell material - form (Staphylococcus) or digest (S. aureus) blood clots |
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antigenic variation
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- vary surfaces Ags to avoid host adaptive immunity
- when host mounts response to fimbriae or flagella, change to different version of it so Abs don't bind to you |
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invasion
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the ability of a pathogen to enter into host cells or tissues, spread, and cause disease
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invasins
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- penetrate host cytoskeleton
- rearrange actin in host cytoskeleton |
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invasin
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- surface proteins that bind host cell membrane and induce entry
- e.g. Salmonella, E. coli "membrane muffling" |
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iron
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hosts are really good at not giving up what?
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siderophores
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- compounds made and secreted by microbes when Fe is scarce
- bind Fe tightly - can be taken up by specific receptors on cell - gene expression: cell only make if Fe is limited |
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toxins
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- poisonous substances produced by certain microbes
- indirect damage to host |
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toxins
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- often primary virulence factor contributing to disease
- can produce fever, diarrhea, shock, destroy blood cells, disrupt nervous and cardiovascular systems, etc. |
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endotoxin and exotoxin
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what are the two main types of toxins?
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endotoxin
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lipid A portion of the LPS in the outer membrane of gram-negative bacteria
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exotoxin
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produced inside some bacteria and secreted into the environment (actively or when cell lyses)
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endotoxin
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- released when cells die/cell wall undergoes lysis
- fever, chills, weaknes, aches, even shock/death |
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endotoxin
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- Lipid A in the outer membrane of gram-negative bacteria
- stimulate macrophages to release certain cytotoxins at uber-high levels = toxic to body |
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gram-negative bacteria
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antibiotics that target what type of bacteria can lyse the bacterial cells, leading to an immediate worsening of symptoms
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exotoxin
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- proteins, often enzymes
- mostly gram-positive - often tiny amounts are harmful, b/c enzymes can work over and over again |
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exotoxins
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- most genes are encoded on plasmids or phages
- soluble in body fluids, so easily diffuse into blood and are transported throughout the body |
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exotoxin
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- work by destroying parts of the host's cells or by inhibiting certain metabolic functions
- often highly specific, and some are potent/lethal in minute amounts |
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exotoxin
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- disease is caused by tiny amounts of the toxin, not by bacterium itself
- bacteria don't always have to be present, or actively infect - e.g. botulism |
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antitoxins
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antibodies that provide immunity to toxins
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heat or chemicals
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since exotoxins are proteins, they can be denatured/inactivated by what?
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toxoids
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- inactivated toxins
- can't cause disease - can stimulate the body to produce antitoxins |
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- A-B toxins
- membrane-disrupting (cytolytic) toxins - superantigens |
what are the types of exotoxins?
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A-B toxin
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examples include Corynebacterium diphtheriae toxin and Clostridium botulinum
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A-B toxin
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- first toxins to be studied
- most common type of exotoxin |
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active enzyme component
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what does the "A" in A-B toxin stand for?
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binding component that attaches to a host cell receptor
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what does the "B" in A-B toxin stand for?
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V. cholerae enterotoxin
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- intestinal exotoxin
- epithelial cells secrete ton of fluid/electrolytes |
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membrane-disrupting toxins
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- some form protein channels
- others disrupt phospholipids |
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cytolytic
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host cell lysis
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superantigens
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- bacterial proteins (antigens) that provoke very intense, uncontrolled immune response
- fever, nausea, vomiting, diarrhea, shock, death |
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superantigens
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- non specifically activate proliferation of T cells, which release tons of cytokines
- S. aureus different strains: enterotoxin and toxic shock syndrome - streptococcus pyrogenes |
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plasmids
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- can encode virulence factors
- R factors: resistance to multiple antibiotics - tetanus neurotoxin, staphylococcus enterotoxin |
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phages
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- often expressed when it goes lysogenic
- incorporate their viral DNA into host cell chromosome - e.g. Diphtheria toxin, botulinum neurotoxin, streptococcus pneumoniae capsule, shiga toxin of E. coli O157 |
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pathogenicity islands
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- large sections of chromosome
- encode a lot of their virulence factors - e.g. Salmonella, N. gonorrhoreae |
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- adsorption
- intracellular - attack immune cells directly |
how do viruses evade host defenses?
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contact inhibition
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cancer-causing viruses stop what which can lead to unchecked growth?
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contact inhibition
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normal host cells stop growing when they come in contact with another cell
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virus infection
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what can induce host cell interferon production, which protects neighboring cells from infection?
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fungi
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- virulence factors not well defined
- toxins, allergies, proteases, protein synthesis inhibition |
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protozoa
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- waste products
- host cell invasion (malaria) - macrophage entry (toxoplasma) - immune evasion |
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algae
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- few are pathogenic
- often produce neurotoxins - e.g. red tides, paralytic shell fish food poisoning |
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helminths
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- damage host cells and tissues as they grow and reproduce
- round worm blocks lymphocyte circulation |
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secretions
excretions discharges shed tissue |
how do most pathogens leave?
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respiratory and GI tract
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what are the most common portals of entry and exit?
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