1. What is CFU Calculation?

CFU (Colony Forming Units) calculation is a method used in microbiology to estimate the number of viable microorganisms in a sample. It's essential for quantifying bacterial or fungal concentrations in various applications.

2. How Does the Calculator Work?

The calculator uses the CFU formula:

Where:

• \( colonies \) — Number of colonies counted on the plate
• \( dilution \) — Dilution factor of the sample
• \( volume \) — Volume of diluted sample plated (mL)

Explanation: The formula accounts for the dilution series used to prepare countable plates and calculates the original concentration in the sample.

3. Importance of CFU Calculation

Details: Accurate CFU calculation is crucial for determining microbial load in food safety testing, water quality analysis, pharmaceutical manufacturing, and clinical microbiology.

4. Using the Calculator

Tips: Enter the number of colonies counted, the dilution factor used, and the volume plated. All values must be valid positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is an ideal colony count range?
A: For accurate counting, plates should ideally have between 30-300 colonies. Counts outside this range may be less reliable.

Q2: How do I choose the right dilution factor?
A: Use serial dilutions to ensure at least one plate falls within the countable range (30-300 colonies).

Q3: What if I have multiple countable plates?
A: Calculate CFU for each countable plate and report the average, or use the plate with counts closest to 150 colonies.

Q4: How should I report CFU results?
A: Report as CFU/mL (for liquids) or CFU/g (for solids), typically in scientific notation for very high or low concentrations.

Q5: What are the limitations of CFU counting?
A: CFU only counts viable cells that can grow under the specific conditions used. It doesn't account for dead cells, viable but non-culturable cells, or cells that grow in clusters.