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42 Cards in this Set
- Front
- Back
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4 steps for Gram stain |
1. Crystal Violet (primary stain) 2. Gram's Iodine (mordant) 3. 95% Ethanol (decolorizer) 4. Safranin (red counterstrain) |
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What step is the most important for determining gram + from -? Why? |
3. 95% Ethanol decolorizer Only gram - will be destained, gram + remain purple
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Gram + stains (purple/pink) |
purple |
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T/F Safranin counterstrain only stains gram - pink/red |
FALSE both are stained by Safranin, but gram + is already purple so it doesn't show |
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What organism is acid fast stain used to identify? Why? |
mycobacterium sp.
Gram stain doesn't work on this species bc there is a hight content of mycolic acid |
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3 Steps for Acid Fast stains (Ziehl-Neelsen Method) |
1. Carbol-fuschin red (primary stain) 2. HCl/alcohol (decolorizer) 3. Methylene blue (counterstrain for non-acid fast orgs.) |
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2 Steps for Capsule/Negative Stain |
1. culture bacterium in skim milk medium 2. congo red & crystal violet stain added |
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How can you differentiate whether or not a bacteria has a capsule using negative stain? |
If capsule is present, it will not stain, leaving a halo around the bacterial cells |
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Endospore (christmas) staining technique turns spores _______ & vegetative cells ___________
Using what stains? |
spores- green (malachite green) vegetative cells- pink/red (safranin) |
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What type of media culture?
Designed to grow most microorganisms Does NOT contain growth inhibitors Ex: Blood agar medium |
General purpose |
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What type of media culture?
Designed to favor distinct groups Inhibits other groups Ex: PEA agar |
Selective |
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What type of media culture?
Designed to distinguish btwn organisms w/ defined metabolic activity (visual rxn occurs) Ex: Simmons Citrate Agar (green to blue rxn)
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Differential |
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What culture media? supports staphylococcus aureus growth both selective & differential How does it work? |
mannitol salt agar
selective- 7.5% salt inhibits all but staphylococcus differential- staphylococcus aureus ferments manitol (red--> yellow)
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What culture media? selective supports gram + inhibits gram - |
PEA
(CNA does opposite) |
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What (2) culture media? selective & differential supports gram - lactose fermentors (E. coli)
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MacConkey & EMB
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How does MacConkey work? |
selective- bile salts inhibit gram + differential- lactose fermentation changes medium from light red to dark pink colonies |
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How does EMB work? |
selective- methylene blue & eosin inhibit gram + differential- lactose fermentation results in metallic-green colonies |
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What culture media? Selective & differential Supports Nisseria sp. How does it differentiate btwn Neisseria gonorrhoeae & Neisseria meningitidis? |
Thayer-Martin
Gonorrhoeae= small, gray/white/colorless Meningitidis= medium/large, blue-gray
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What (2) culture media? Selective & differential Supports nonfermenters Shigella & Salmonella Differentiates Salmonella |
XLD & Hektoen-Enteric |
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How does XLD differentiate Salmonella? |
Salmonella produces H2S which reacts w/ ferric ions to produce black precipitate |
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How does Hektoen-Enteric differentiate Salmonella? |
Salmonella reduces thiosulfate in agar & produces black precipitate |
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What culture media? Selective for Yersinia Sp. |
CIN
(Yersinia sp, appear as colonies w/ red dot in middle) |
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What culture media? Selective for corynebacterium sp. |
Tinsdale (chocolate tellurite, loefflers)
(Corynebacterium sp. reduce metal tellurate to form black precipitate, surrounded by gray halos) |
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What culture media? Selective & Differential Supports Vibrio sp |
TCBS
(vibrio sp. causative in cholera, diarrhea, food poisoning) |
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What culture media? Selective for Legionella sp. |
BCYE |
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What culture media? Differentiates microorganisms w/ lecithinase activity (Clostridium sp.) How does it work? |
Egg yolk agar
lecithinase degrades phospholipids into insoluble diglycerides forming opaque zones around colonies |
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What culture media? Selective Supports Mycobacterium Sp. Inhibits all others by malachite green |
Lowenstein-Jensen (egg-based medium) |
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What culture media? Selective for Bordetella Pertussis Inhibits all others by Methicillin |
Bordet-Gengou (Potato-glycerol based) |
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Which enzyme is used to test btwn Staphyloccocus & Streptococcus by producing bubbles (+ result)? Which one is +? |
Catalase
Staphylococcus is + (bubbles) |
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Which enzyme is used to test for the presence of staphylococcus aureus? What will happen if it is present (+ result)? |
coagulase
fibrinogen binding causes agglutination of microorganisms (at bottom of tube) |
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Which enzymes identifies Neisseria, by breaking it down into purple indophenol? |
oxidase |
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Which enzyme tests for tryptophanase activity (E.coli), by turning yellow to red)? |
Indole |
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What enzyme leads to the release of ammonia and is used to identify Proteus sp. by a color change from pale orange to pink? |
Urease |
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What test identifies CO2 production and is + for Enterobacter clocae? How does it work? |
Citrate Utilization Test
CO2 leads to pH rise, turns bromthymol blue indicator from green to bright blue (+ result) |
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What test can be used to identify Group D streptococci or Enterococcus, through a color change from orange to black (+)? |
Bile esculin test
(color change results from esculin hydrolysis) |
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What + test results in a clear zone around substrate in methyl green dye? |
DNAse test
(methyl green dye releases DNA= clear zone, + for DNA presence) |
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What test can be used to identify streptococcus pneumoniae by creating a clear zone of inhibition on the strep plate? |
Optochin Test/ P-disc
(streptococcus is sensitive to optochin & forms zone of inhibition around optochin innoculation on plate) |
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What test can be used to differentiate group A streptococci (S. pyogenes (strep throat) from other beta-hemolytic strep? |
Bacitracin Susceptibility / A disc
other types will not from zone of inhibition around bacitracin innoculation |
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Which fungal stain attaches to fungal walls, staining pink, and reacts w/ aldehyde groups to form a red-purple product? |
Periodic acid-Schiff stain |
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Which fungal stain is used for Candida, Histoplasma, & Blastomyces fungi & stains black? |
Grocott-Gomori methenamine-silver nitrate stain |
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Which fungal stain detects Histoplasma capsulatum in blood or bone marrow & stains yeast purple-blue surrounded by clear halo? |
Giemsa stain |
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Which fungal stain is used for brain and other tissue to stain melanin in the fungal cell wall & turn it brown? |
Masson-Fontana stain |
