Table of Contents
- 1 Why do you count plates with 20 200 colonies in the spread plate technique and plates with 30 300 colonies in the pour plate technique?
- 2 Why are plates with 30 to 300 colonies used for calculation?
- 3 What is TNTC and Tftc?
- 4 Why are plates with more than 300 colonies not considered viable quizlet?
- 5 What does 30 billion CFU mean?
- 6 What is the purpose of the spread plate technique?
- 7 How are bacteria isolated from a spread plate?
Why do you count plates with 20 200 colonies in the spread plate technique and plates with 30 300 colonies in the pour plate technique?
Count the number of colonies on each plate. The countable plate has between 30 and 300 colonies. More than 300 colonies would be difficult to count, and less than 30 colonies is too small a sample size to present an accurate representation of the original sample.
Why do you count only 25-250 colonies per plate in determining populations?
Ideally only plates with 25-250 colonies are used. Counts above 250 are considered Too Numerous To Count (TNTC) because it is impossible to tell whether colonies are separated. Plates with less than 25 colonies do not have a statistically significant number of colonies.
Why are plates with 30 to 300 colonies used for calculation?
Why do we use plates with between 30-300 colonies in enumeration? Plates with more than 300 colonies are difficult to count, and plates with less than 30 colonies give statistically unreliable numbers of colonies to count.
Why are plate count results often expressed as colony forming units?
Counting with colony-forming units requires culturing the microbes and counts only viable cells, in contrast with microscopic examination which counts all cells, living or dead. Expressing results as colony-forming units reflects this uncertainty.
What is TNTC and Tftc?
◦ TNTC (Too Numerous To Count): more than. 300 colonies. ◦ TFTC (Too Few To Count): less than 30 colonies. Page 4.
Why is it necessary to use only diluted cultures that contain 100 to 200 cells for a successful spread plate?
Why is it necessary to use only diluted cultures that contain 100 to 300 cells for a successful spread plate? to avoid colonies if cultures are not diluted the colonies will grow too thick. therefore not allowing good visualization of individual colonies.
Why are plates with more than 300 colonies not considered viable quizlet?
why are only plates with 30-300 colonies considered countable? The plates with less than 30 colonies are not statistically significant and plates with greater than 300 colonies are not considered valid because they may not have provided adequate nutrients for all cells to grow to form colonies.
How do you count your total plate count?
Plate counting method
- Step One: Diluting the sample.
- Step Two: Plating the sample.
- Step 3: Incubating the plates.
- Step 4: Counting the colonies.
- Step 5: Determining how many viable organisms were in the original sample.
What does 30 billion CFU mean?
colony-forming units
This stands for ‘colony-forming units’, and is the scientific term for the number of viable bacteria within a sample; in this case, in a friendly bacteria supplement. In other words, if a supplement has a CFU of 5 billion, it means that it contains 5 billion individual live cultures.
How to calculate the colony count of a spread plate?
Once you count the colonies, multiply by the appropriate dilution factor to determine the colony-forming units (CFU) present per ml in the original sample. CFU/ml = (no. of colonies x dilution factor) / volume of culture plate For example, suppose the plate of the 10^6 dilution yielded a count of 130 colonies.
What is the purpose of the spread plate technique?
Spread plate technique is a viable counting method employed to plate a liquid sample for the purpose of isolating or counting the bacteria present in that sample. A perfect spread plate technique will result in visible and isolated colonies of bacteria that are evenly distributed in the plate and are countable.
Which is the countable range for spread plates?
ASTM provides countable ranges of 20-80 CFU/membrane, 20-200 for spread plates and 30-300 for pour plates (7). The FDA Bacterial Analytical Manual (BAM) recommends 25-250 CFU/plate as a countable range (8).
How are bacteria isolated from a spread plate?
A successful spread plate will have a countable number of isolated bacterial colonies evenly distributed on the plate. Spread plate culture technique is among the most widely used culture technique for isolating the bacteria.