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62 Cards in this Set
- Front
- Back
5 types of microscopes
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Light
Dark-field Phase-contrast Fluorescent Electron |
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Purpose of Darkfield microscope
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to allow the viewing of bacteria that don't take stains well like spirochaetal.
-light shone from angle bends off bacteria to make a dark background the bacteria show white/light against it. |
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phase-contrast microscopy
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take avtg of varying slide densities.
enhances varying wavelengths via PHASE PLATE specimen appears dark |
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what color is
flourescein rhodamine |
green
red |
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flourescence microscopy
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certain material emits energy detectable as visible light when irradiated with UV light.
Emission filter sorts out lower energy emitted light. bacteria stain with flouresc. dye |
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are most bacterial stains positive or negative?
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positive, because bacteria have a net negative charge.
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principle of differential stain
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allows to differentiate between groups of bacteria on basis of some property, usually the cell wall.
uses a primary dye and a counterstain. |
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negative stains - what for
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to see particular characteristic that won't stain with a positive stain.
CAPSULES are only visible with neg. |
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capsule stain
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india ink stains background so bacteria shows up as transparent
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electron microscope
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specimen scatters electrons based on its varying densities.
used in virology, but not very useful cuz we have better techniques. |
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2 major components of outer layer of bacterial cell
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1. Glycocalyx
2. Cell wall |
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glycocalyx - what is it, why?
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-the outermost layer of bacteria.
-made of polysaccharides or polypeptides -if compact/thick = capsule -if loosely arranged = slime layer FUNCTION to protect bacteria from phagocytosis -allows it to adhere to tissue in host. |
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cell wall - where, why?
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Just inside bacterial glycocalyx
Function: -To protect bacteria, maintain rigidity. Different in Gram + and - |
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Layers in Gram + cell wall
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1. peptidoglycan = 90%
2. teichoic acid/lipoteichoic acid = 10% |
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which has more layers, gram + or -
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negative! thinner than positive though
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3 layers of neg cell wall
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1. outer membrane - made of lipopolysaccharides, lipoprotein, and porin proteins.
2. peptidoglycan 3. periplasmic space |
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2 cell inclusions
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Granules
Endospores |
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purpose of granule cell inclusions
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store food, they're visible when stained
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purpose of sporulation
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survival mechanism in adverse environmental conditions like dehydration, temperature extremes, or uv light
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Steps of Sporulation
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1. DNA copied
2. Invaginate cell membrane btwn 2 DNAs 3. Forespore - early coat around nucleic acid. 4. Cell wall forms 5. Cell coat forms - resistant to adverse conditions, also STAIN so we see a hole. |
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Only 2 genera that produce spores:
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Aerobic Bacillus and
Anaerobic Clostridium both are gram positive |
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difference between sporogenesis and germination
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sporogenesis is the forming of a spore
germination is the spore going into a vegetative state. |
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the four amino acids in a glycan tetrapeptide
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l-alanine
d-alanine lysine or diaminopimelic acid d-glutamic |
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peptidoglycan structure
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parallel diagonal lines of alternating G/M/G/M;
G=n-acetyl glucosamine M=n-acetyl muramic acid M's are linked vai glycan tetrapeptide; Tetrapeptide: M-aa-aa-aa-aa |interbridge|aaM |
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4 types of classification of Flagella
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Peritrichous - lots around
Monotrichous - one flagell. Lophotrichous - LUMP of flag. Amphitrichous - single flagellum at both poles! Polar - number or singular |
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auxotroph
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a bacterium that was originally a prototroph and now has developed a specific growth requirement for its media.
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halophile
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salt-loving bacteria - give it to its media
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media enrichers
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-Growth factors (blood, carbs, NaCl, Vitamins, Amino acids
-Salt etc |
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enrichment media
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suppresses normal flora while enhancing pathogen growth
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enrichment vs. enriched media
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enrichment enhances all bacterial growth
enriched only enhances growth of bacteria we want to see, not normal flora |
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3 components of gram negative outer membrane
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-lipopolysaccharides (LPS)
-lipoproteins (anchor outer cell membrane) -porin protein - gets nutrients/proteins into the negative wall |
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what is contained in the periplasmic space, what type of organism has it?
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gram negative
contains enzymes for nutrient breakdown |
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what is a mesosome?
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an extension of the cell membrane; it increases the surface area of the membrane for increased uptake of nutrients.
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whats in bacterial cytoplasm?
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3 things:
-chromatin - throughout the cell, no nucleus. -ribosomes - for protein synthesis. -granules - for food storage. |
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3 possible shapes of bacteria
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-cocci
-bacilli -spirilla |
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3 structural componnts of flagella
-type of motion |
a. filament
b. hook c. basal body -rotary |
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important info if organism is ACID FAST:
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MYCOBACTERIUM
-not whether its pathogenic or not, but at least you know its mycobac. |
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beading
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seen in mycobacterium, when the acid fast organisms don't take up the stain evenly.
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cording
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when mycobacteria grow with cells lying end to end.
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q.c. on acid fast stain?
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2 organisms: red bacilli and blue cocci. so mycobacterium and staph aureus.
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chemical component of mycobacterium that makes them acid-fast and resistant to decolorizing:
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-Mycolic acid - waxy lipid, 60% of wall.
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3 types of cell-wall deficient bacteria:
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a. L-forms
b. Protoplasts/Spheroplasts c. Mycoplasma |
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L-forms
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Lister-forms of bacteria - really are normal but their cell walls have been lost due to high penicillin doses, or high salt. Removing such conditions returns the cell wall to normal.
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Protoplasts vs. spheroplasts
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L-forms of Gram positive, and L-forms of Gram negative.
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Mycoplasma
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special bacteria that does not have a cell wall. Responsible for walking pneumoniae.
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2ndary pathogens
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cause a disease because a primary pathogen made the host weak
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opportunistic pathogens
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cause a disease because another disease or condition (not necessarily pathogen) made the host weak.
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nosocomial pathogens
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hospital pathogens. often resist antibioitics.
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communicable vs. contagious
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Anthrax is communicable from animals to humans, but not contagious between humans.
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contagious
communicable |
it can be given directly to a person
it can be carried by a person |
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components of a chain of infection:
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Type of disease
communicable? Source Transmit method Entry Port Effect on host inoculum size Infection site Infection type Infection stage Sequelae Exit port |
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3 possible sites of infection
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-localized (at point of entry)
-focal (extends beyond entry point) -systemic (carried by blood/lymph) |
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5 types of infection
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-acute
-chronic -subacute (may not know have it) insidious (very slow) asymptomatic (subclin, inapparent, carrier) -latent - viruses are this. |
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4 stages of infection
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incubation - entry, incubate, then symptoms.
prodrome - time betwn incub/no symptoms and symptoms of disease - impending doom disease - fastigium is peak of symptoms. convalescence - fewer/milder symptoms, getting better. |
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sequelae
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sometimes worse than the initial infection, the post-infection infection.
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port of exit
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same as port of entry; gi tract, respiratory, skin, mucosa, etc.
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Infection meets Koch's postulates if:
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-present in every animal with disease, not in healthy animals.
-microorg can be grown in pure culture in lab from an animal specimen. -can inoculate healthy animal with cultured isolate and see disease. -can isolate microorg from 2nd animal and grow in lab for identical result to original isolate. |
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8 steps to identify agent causing infection
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1. Collect specimen
2. Direct tests 3. Inoculate media 4. Incubate 5. Observe macro morpho 6. Observe micro morpho 7. ID tests 8. Antibiotic susceptibility tests |
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types of specimen collection
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saliva, sputum, blood, clean catch, catheter, vaginal swab/stick
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3 types of direct specimen tests
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direct smear - gram stain it
immunological tests - for spcfc Ag. direct molecular tests - nucleic acid |
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4 types ID tests in lab
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1. Biochemical - media has tests in it
2. Immunological - detect antigens 4. Serological -detect antibody in serum 4. Molecular -detect unique nucleic acid |
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3 methods of indirect transmission of a pathogen
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-Fomite (inanimate object)
-Vector (bugbite/transfusions) -Droplet nuclei |