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 calculated by counting colonies on a culture plate and applying dilution and volume factors.

2. How Does The Calculator Work?

The calculator uses the CFU formula:

Where:

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

Explanation: This formula accounts for the dilution series used to obtain countable colonies and normalizes the result to colony forming units per mL of the original sample.

3. Importance Of CFU Calculation

Details: CFU calculation is essential for quantifying bacterial concentrations in various applications including water quality testing, food safety monitoring, clinical microbiology, and research experiments.

4. Using The Calculator

Tips: Enter the number of colonies counted, the dilution factor used, and the volume plated. All values must be positive numbers. For accurate results, plates should have between 30-300 colonies.

5. Frequently Asked Questions (FAQ)

Q1: Why is the dilution factor important in CFU calculation?
A: The dilution factor accounts for the series of dilutions performed to obtain a countable number of colonies, allowing calculation back to the original sample concentration.

Q2: What is the ideal range of colonies for accurate counting?
A: 30-300 colonies per plate is generally considered the statistically reliable range for accurate counting.

Q3: How should I report CFU results?
A: Report as CFU/mL (or CFU/g for solid samples) with appropriate significant figures based on your counting accuracy.

Q4: What if my plate has too many colonies to count?
A: If colonies are too numerous to count (TNTC), you need to use a higher dilution factor and replate the sample.

Q5: Are there limitations to CFU counting?
A: CFU counts only detect viable cells that can grow under the specific conditions used, and may not represent the total microbial population.