Which dilution method is used in standard plate count method?
Which dilution method is used in standard plate count method?
The standard plate count method consists of diluting a sample with sterile saline or phosphate buffer diluent until the bacteria are dilute enough to count accurately. That is, the final plates in the series should have between 30 and 300 colonies.
Why We Do dilution in plate count method?
We use serial dilutions to create decreasing concentrations of the original sample that are then plated so that a plate will be created with a low enough number of bacteria that we can count individual colonies. From that number, we can calculate the original cell density in the broth.
What is plate dilution?
Dilution plating is a simple technique used to estimate the number of heterotrophic bacteria in an environmental sample. Dilution plating is based on serial dilution of the sample. Serial dilution involves repeatedly mixing known amounts of source sample or culture with sterile liquid, usually a low-molarity buffer.
What is a dilution factor of viable plate?
Since each colony on an agar plate theoretically grew from a single microorganism, the number of colonies or Colony Forming Units is representative of the number of viable microorganisms. Since the dilution factor is known, the number of microorganisms per ml in the original sample can be calculated.
What is standard plate count technique?
The Standard Plate Count (SPC) means the colony count of the mesophilic bacteria growing under aerobic condition on standard methods agar (Plate Count Agar), and SPC becomes the representative index indicating the degree of the microbial contamination of the food. Generally, the standard methods agar is used for SPC.
What is the difference between pour plate and spread plate method?
The key difference between Pour plate and Spread plate is that a known volume of the sample is spread on the surface of the agar medium in spread plate, while, in pour plate, a known volume of the sample is mixed with agar and then poured into a plate.
What is the pour plate method used for?
The pour plate technique can be used to determine the number of microbes/mL in a specimen. It has the advantage of not requiring previously prepared plates, and is often used to assay bacterial contamination of food stuffs.
What is the difference between total plate count and standard plate count?
The APC term stands for aerobic plate count, but again is interchangeable with the others. Other terms used more historically are Standard Plate Count, Mesophilic Count or Total Plate Count these too generally refer to aerobic bacteria able to grow at average temperatures (e.g. 30 to 40°C).
How is the plate count of a sample calculated?
That is why, instead of expressing the counts of bacteria as ‘No. of bacteria/gm or ml of sample’, it is very often expressed as number of colony forming units per gm or ml (CFU/gm or ml). The total plate count (TPC) in the original sample is calculated by multiplying the number of CPUs with the respective dilution factors.
How to calculate bacterial count for pour plate technique?
For pour plate technique, bacterial count is No.X 10 c /gm, where c = dilution factor. For spread plate technique, bacterial count is No. X10 c+1 /gm, where c = dilution factor. The number is converted to two decimal places in the form of (x.yz X 10 m). For example, 288 X 10 4 is expressed as 2.88 X 10 6.
What is the formula for the spread plate method?
The spread plate method is used for viable plate counts. In this method, the total number of colony-forming units ( CFU) on the surface of an agar medium is enumerated. The Calculation of CFU/mL is done by using the formula: CFU/mL= CFU * dilution factor * 1/aliquot (the volume of diluted specimen (aliquot) is either 0.1 or 1.0 mL).
What is the principle of the pour plate method?
Principle of Pour Plate Method In this Method, serial dilutions of the inoculum (serially diluting the primary specimen) are added within sterile Petri plates to which is poured melted and cooled (42-45°C) agar medium and completely mixed by revolving the plates which are then left to solidify.