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In microbiology, a colony-forming unit (CFU, cfu or Cfu) is a unit which estimates the number of microbial cells (bacteria, fungi, viruses etc.) in a sample that are viable, able to multiply via binary fission under the controlled conditions. Counting with colony-forming units requires culturing the microbes and counts only viable cells, in ...
Once a plate has been successfully prepared, plate count agar cells will grow into colonies which can be sufficiently isolated to determine the original cell type. The colony-forming unit (CFU) is an appropriate description of the colony's origin. In plate counts, colonies are counted, but the count is usually recorded in CFU.
The count represents the number of colony forming units (cfu) per g (or per ml) of the sample. A TVC is achieved by plating serial tenfold dilutions of the sample until between 30 and 300 colonies can be counted on a single plate. The reported count is the number of colonies counted multiplied by the dilution used for the counted plate
The plate count method relies on bacteria growing a colony on a nutrient medium so that the colony becomes visible to the naked eye and the number of colonies on a plate can be counted. To be effective, the dilution of the original sample must be arranged so that on average between 30 and 300 colonies of the target bacterium are grown.
In the Plate Count Method, the sample of drug product to be tested and Soybean-Casein Digest Broth is poured into a Petri dish. [4] The Petri dish is then incubated. The most probable number method (MPN) can also be performed for products considered to have a low bioburden [ clarification needed ] .
Such homogeneously spread colonies are suitable for CFU enumeration. To quantify the number of cells in a culture, the cells can be simply plated on a petri dish with growth medium. If the cells are efficiently distributed on the plate, it can be generally assumed that each cell will give rise to a single colony or Colony Forming Unit (CFU ...
An appropriate volume is then combined with melted agar to produce plates in which the final antibiotic concentrations represent a 2-fold dilution series. After this, bacteria prepared to a standard concentration are added as a spot to each plate, with 10 4 colony forming units (CFU) per spot.
It is often necessary to vary the volume of water sample filtered in order to prevent too few or too many colonies from forming on a plate. Bacterial colonies can be counted after 24 to 48 hours depending on the type of bacteria. Counts are reported as colony forming units per 100 mL (cfu/100 mL).