Microbiology Exam 2 Answers

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Steriliaztion
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No living cells, spores, or viruses

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Disinfectant
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Killing, inhibiting, removing organisms that cause disease, from inanimate objects
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Sanitization
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reducing microbials numbers to levels safe for the public

-dishwasher

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Antiseptics

 

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kill or inhibit infection causing organisms from living tissues

-what you put on a wound

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Germicides
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kill a certain organism

-fungicide, viricide, bactericide

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Physical Agents
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  • Heating-doesnt kill spores
  • Autoclave-kills all cells and spores
  • Pasteruization-doesnt kill spores
  • Baking-kills all cells and spores
  • Filtration-just removes
  • UV-damages DNA 

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Factors affecting anti-microbial efficiency
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  • Population size
  • Population composition
  • Temperature
  • Concentration of anti-microbial agent
  • Length of exposure
  • Local environment

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5 Modes of Killing
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  • Bind to ribosomes, stop translation
  • Stop cell wall synthesis
  • Disrupt membranes
  • Stop nucleic acid synthesis
  • Inhibit metabolic pathways

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Bacterial Mechanisms of Antibiotic Resistance

 

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  • Prevent drug entrance
  • Efflux pumps-nonspecific 
  • Drug inactivation-making an enzyme that deactivates the drug coming in
  • Target modification-changes to RNA sequences in the ribosomes, alterations in tetrapeptide, alternative metabolic pathways

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2 ways bacteria acquire drug resistance genes
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  • Spontaneous mutations
  • Horizontal gene transfer-sharing genes, conjugation

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Symbiosis
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organisms that spend any portion of their life associated with an organism of another species
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Commensal
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1 benefits, the other is neither harmed nor benefits

-bacteria on our skin, gut

 

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Mutualistic
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Both organisms benefit

 

-Lichens

-Deep sea H2S vents

-Ruminants

-Termites

-Green flat worms

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Parasitism
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Any disease causing pathogen, 1 benefits and 1 is harmed; least common type of symbiosis

 

-Photosynthetic sea slugs

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Normal flora
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Organisms that routinely reside on the body’s surface

*not in lungs!

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How are normal flora protective?

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  1. compete for attachment with pathogenic bacteria
  2. produce antimicrobial substances that fight off and help destro pathogenic bacteria
  3. stimulate the immune system, keeps immune system slightly activated

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Infection
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when a parasite is multiplying in/on a host
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Infectious disease

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host cannont function normally due to presence of parasite or its products
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Pathogens

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cause disease
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Pathogenicity
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organisms ability to cause disease
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Virulence

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degree or intensity of pathogenicity, as indicated by morbidity and mortality rates
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Three factors affecting parasitiism

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  1. # of organisms inoculated
  2. virulence of organism
  3. hosts degree of resistance;

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Symptoms

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subjective (cant see it)

nausea, pain, loss of apetite;

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Signs

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something you can observe

rash, fever, swelling

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Infectious disease process;
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[image]
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Exotoxins-4 types
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  • neurotoxins- affect nervous system
  • enterotoxins- affect GI tract
  • cytoxins-affect cellular function
  • superantigens** unique! over stimulate the immune system, become leaky, 20% of T cells activated

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Endotoxins

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LPS

only gram negative

sluffed off when gram negative dies

weak immune response

no vaccine made for it

multiorgan failure

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Innate Immunity Barriers

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  • Physical Barriers: skin, GI tract, mucous, respiratory tract, genitourinary tract, eye
  • Chemical Barriers: antimicrobial peptides**
  • Molecular defenses: complement, type I interferons
  • Cellular Defenses
  • Inflammation
  • Fever

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Antimicrobial peptides

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  • Defensins: found in skin and punch holes in bacteria membranes
  • Histanin: has antifungal activity, targets mitochondrial membrane inside of fungus-very specific
  • Lactoferrin and Transferrin-bind to iron so microbes cant get it
  • baceriocin: (bacteria make this one), produced by normal flora, defense against other bacteria

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Complement functions
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  • Opsonization:components bind to viruses and bacteria to be better taken up by macrophage
  • Direct lysis of bacteria-forms pore causing it to lyse
  • Inflammation;

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Cytokines

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protein communication molecules

IL-2, IL-4, Type I interferons

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Granular cells

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Toxic molecules

  • Mast cells-release histamine
  • Neutrophils-first reactors, phagocytosis
  • Basophils-release histamine
  • Eosinophils-first parasities, allergies

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Agranular Cells

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Not toxic

  • T cells
  • B cells
  • Macrophages-present antigen to T cells, phagocytosis
  • Dendritic cells-present antigen to T cells, phagocytosis
  • Natural Killer cells-kill infected cells and tumor cells

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Chemical mediator HISTAMINE
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  • **Cause inflammation
  • Activation of vascular endothelium
  • Increase vascular permeabillity
  • Increase vasodilation (blood slows down)
  • Sticky adhesion goes up

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4 Major Benefits of Fever

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  1. Slows the growth rate of microbes
  2. Inactivates some bacterial toxins
  3. Increases immune system activity
  4. Forces a person to fill ill and allows for rest for energy to be restored

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Primary Response
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First exposure to a given antigen, slow to develop therefore innate immunity attempts to provide protection
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Secondary Response

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Memory Respsonse

response is more robust and faster

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Antigen

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a substance that the body sees as foreign or non self, and to which it mounts an immune response
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Epitopes

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proteins have epitopes, or short amino acid sequences that are recognized by antibodies and T Cells

*for each epitope there is a B cell

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IgM

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first antibody secreted during first infeciton, pentameric
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IgD

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stays membrane-bound to B cell, function unknown
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IgG
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most abundant antibody in the blood, during second infection, crosses placenta and present in serum, small
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IgA

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located mostly at mucosal surfaces, very important in binding up pathogens before they can get deeper into the body, dimeric
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IgE
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cause of allergies, constant region binds to cell surfact of mast cells and basophiles activating them to secrete histamine when the antibody binds to pollen
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Whole organism vaccines

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  • Live attenuated-live passaged in culture until no longer pathogenic but still immunogenic
  • Inactivated or killed-killed with heat or chemicals, but still immunogenic

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Subunit vaccines

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  • Toxoids-exotoxin inactivated, “fake toxin”
  • Polysaccharide capsules- S. pneumoniae
  • Viral glycoproteins
  • Recombinant or native proteins

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DNA vaccines

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inject with plasmids that express antigens in host tissues

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**need to add adjuvants because plasmids get lost in our big human body so adjuvants trigger danger signals better at ativated T cells, adjuvants can also be toxic

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Recombinant vector vaccines

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*use of viruses or bacteria to deliver genes of interest;

Dr. Taylor tried this with TB

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Ability to grow in or on host

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  • must have correct pH
  • must have correct temp
  • correct O2 content
  • hemolysins-lyse, RBC, anemia

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Coagulase

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forms clot around microbes

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avoid host immune system

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IgA protese
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cleaves IgA-which is at mucosal surfaces
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Leukocidins
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kill lysosomes in WBC
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Protein A

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binds to IgG stops complement binding
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Hiding within a host cell

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avoiding host immune system

survive with phagocyte;

-some bacteria are able to escape the phagosome before phagolysomal fusion

-some able to prevent phagosome and lysosome fusion: TB do this

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Collagenase

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breaks down collagen
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H2O2 and NH3
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damage tissues
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Elastase
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breaks down basement membranes
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Hyaluronidase
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breaks down connections between cells
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Lecithinase
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breaks down plasma membrane
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Leishmaniasis

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an invasive protozoal skin infection
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Intoxications

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damage due to toxins produced b microbe outside of the host’s body entering the host
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Damage to Plasma membranes
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Clostridium perfringens releases alpha toxin which removes the polar heads from the phospholipid bilayer destroying its integrity, breaks down muscle tissue, gas gangrene
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Mucocilliary escalator

 

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ciliated cells and mucous trap andpropel microbes away from lungs and into the throat
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Extravasation

 

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neutrophils squeeze between cellular junctions 

-diapedesis

-inflammation 

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Pyrogens

 

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Substances that cause fever

Exogenous pyrogens: LPS, Exotoxins

Endogenous pyrogens: macrophages release IL-1

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