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10 Cards in this Set
- Front
- Back
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What are two ways of plating diluted bacterial samples?
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-transfer 0.1 ml a sample to center of sterile agar plate and use sterile hockey stick to spread
-transfer 0.1 ml sample to melted agar tube and mix: pour this onto another solid plate and swirl it |
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How long are plates incubated for dilution tests?
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-24 hours at appropriate temperature
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How do you find the CFU's of a plate?
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-count the colonies and locate the "countable plate" (30-300)
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How do you find the SDF of a dilution problem?
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-this is the initial sample or flask (sample dilution factor)
-if undiluted it would be 1/1 -if 1ml substance is diulted with 9 ml water, the SDF would be 1/10 |
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How do calculate the individual tube dilution factor (ITDF)?
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-vol transferred/(vol sample transferred + volume diluent)
-example: 0.1 transferred to 9.9ml would be a 1/100 ITDF |
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How do you find the Total Seris Dilution Factor (TSDF) for a countable plate?
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-multiply ITDF's up to tube used
*do NOT use tubes that came AFTER the countable plate since it wasn't part of the dilution! |
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How do you find the Plating Dilution Factor (PDF)?
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-divide amount transferred by 1 ml
*always compare this to 1ml! |
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Why do you always compare the plated amount transferred to 1 ml?
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-because original concentration is CFU/ml
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How do you find the Final Dilution Factor?
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-SDF x TSDF x PDF
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How do you find CFU/ml in ORIGINAL sample?
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-CFU of countable plate x 1/FDF OR
-CFU/FDF |
