MB II
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- 5 types of microscopes
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Light
Dark-field
Phase-contrast
Fluorescent
Electron - 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. - phase-contrast microscopy
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take avtg of varying slide densities.
enhances varying wavelengths via PHASE PLATE
specimen appears dark -
what color is
flourescein
rhodamine -
green
red - 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 - are most bacterial stains positive or negative?
- positive, because bacteria have a net negative charge.
- 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. - 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. - capsule stain
- india ink stains background so bacteria shows up as transparent
- 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. - 2 major components of outer layer of bacterial cell
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1. Glycocalyx
2. Cell wall - 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. - cell wall - where, why?
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Just inside bacterial glycocalyx
Function:
-To protect bacteria, maintain rigidity.
Different in Gram + and - - Layers in Gram + cell wall
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1. peptidoglycan = 90%
2. teichoic acid/lipoteichoic acid = 10% - which has more layers, gram + or -
- negative! thinner than positive though
- 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 - 2 cell inclusions
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Granules
Endospores - purpose of granule cell inclusions
- store food, they're visible when stained
- purpose of sporulation
- survival mechanism in adverse environmental conditions like dehydration, temperature extremes, or uv light
- 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. - Only 2 genera that produce spores:
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Aerobic Bacillus and
Anaerobic Clostridium
both are gram positive - 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. - the four amino acids in a glycan tetrapeptide
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l-alanine
d-alanine
lysine or diaminopimelic acid
d-glutamic - 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 - 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 - auxotroph
- a bacterium that was originally a prototroph and now has developed a specific growth requirement for its media.
- halophile
- salt-loving bacteria - give it to its media
- media enrichers
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-Growth factors (blood, carbs, NaCl, Vitamins, Amino acids
-Salt
etc - enrichment media
- suppresses normal flora while enhancing pathogen growth
- 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 - 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 - what is contained in the periplasmic space, what type of organism has it?
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gram negative
contains enzymes for nutrient breakdown - what is a mesosome?
- an extension of the cell membrane; it increases the surface area of the membrane for increased uptake of nutrients.
- whats in bacterial cytoplasm?
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3 things:
-chromatin - throughout the cell, no nucleus.
-ribosomes - for protein synthesis.
-granules - for food storage. - 3 possible shapes of bacteria
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-cocci
-bacilli
-spirilla -
3 structural componnts of flagella
-type of motion -
a. filament
b. hook
c. basal body
-rotary - 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. - beading
- seen in mycobacterium, when the acid fast organisms don't take up the stain evenly.
- cording
- when mycobacteria grow with cells lying end to end.
- q.c. on acid fast stain?
- 2 organisms: red bacilli and blue cocci. so mycobacterium and staph aureus.
- chemical component of mycobacterium that makes them acid-fast and resistant to decolorizing:
- -Mycolic acid - waxy lipid, 60% of wall.
- 3 types of cell-wall deficient bacteria:
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a. L-forms
b. Protoplasts/Spheroplasts
c. Mycoplasma - L-forms
- 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.
- Protoplasts vs. spheroplasts
- L-forms of Gram positive, and L-forms of Gram negative.
- Mycoplasma
- special bacteria that does not have a cell wall. Responsible for walking pneumoniae.
- 2ndary pathogens
- cause a disease because a primary pathogen made the host weak
- opportunistic pathogens
- cause a disease because another disease or condition (not necessarily pathogen) made the host weak.
- nosocomial pathogens
- hospital pathogens. often resist antibioitics.
- communicable vs. contagious
- 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 - 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 - 3 possible sites of infection
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-localized (at point of entry)
-focal (extends beyond entry point)
-systemic (carried by blood/lymph) - 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. - 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. - sequelae
- sometimes worse than the initial infection, the post-infection infection.
- port of exit
- same as port of entry; gi tract, respiratory, skin, mucosa, etc.
- 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. - 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 - types of specimen collection
- saliva, sputum, blood, clean catch, catheter, vaginal swab/stick
- 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 - 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 - 3 methods of indirect transmission of a pathogen
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-Fomite (inanimate object)
-Vector (bugbite/transfusions)
-Droplet nuclei