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Cfu Formula:
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CFU (Colony Forming Units) is a measurement used in microbiology to estimate the number of viable bacteria or fungal cells in a sample. It represents the number of cells capable of forming colonies when cultured.
The calculator uses the CFU formula:
Where:
Explanation: The formula calculates the concentration of viable microorganisms in the original sample by accounting for the dilution and plating volume.
Details: CFU calculation is essential for quantifying bacterial or fungal load in various applications including water testing, food safety, clinical microbiology, and pharmaceutical quality control.
Tips: Enter the number of colonies counted, the dilution factor of your sample, and the volume plated. All values must be positive numbers.
Q1: What is an appropriate dilution factor?
A: Dilution factors typically range from 1:10 to 1:1,000,000 depending on the expected microbial concentration. Serial dilutions are often used.
Q2: How many colonies should be counted for accuracy?
A: For statistical reliability, aim for 30-300 colonies per plate. Fewer than 30 may be unreliable, while more than 300 may be too numerous to count accurately.
Q3: What if I have multiple dilution plates?
A: Use the plate with colony counts in the ideal range (30-300) for the most accurate calculation. Average results from multiple valid plates if available.
Q4: Are there limitations to CFU counting?
A: CFU only counts viable cells that can grow under the specific conditions. It doesn't account for dead cells, cells in clumps, or those with different growth requirements.
Q5: How should results be reported?
A: Report as CFU/mL (for liquid samples) or CFU/g (for solid samples), typically in scientific notation for very high or low concentrations.