1. What is CFU/mL?

CFU/mL (Colony Forming Units per milliliter) is a measurement used in microbiology to estimate the number of viable bacteria or fungal cells in a sample. It provides a quantitative assessment of microbial concentration.

2. How Does the Calculator Work?

The calculator uses the CFU/mL 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 obtain countable colonies and calculates back to the original concentration in the undiluted sample.

3. Importance of CFU/mL Calculation

Details: Accurate CFU/mL calculation is crucial for microbiological analysis, quality control in food and pharmaceutical industries, clinical diagnostics, and research applications to determine microbial load in samples.

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, colonies should be between 30-300 per plate.

5. Frequently Asked Questions (FAQ)

Q1: Why is the dilution factor important?
A: The dilution factor accounts for the serial dilutions made to obtain a countable number of colonies (typically 30-300 colonies per plate).

Q2: What is an ideal colony count range?
A: 30-300 colonies per plate is considered ideal for accurate counting. Below 30 may lack statistical significance, above 300 may be too crowded for accurate counting.

Q3: How do I choose the right dilution factor?
A: Based on expected microbial load. For high concentrations, use higher dilutions; for low concentrations, use lower dilutions or no dilution.

Q4: Can this calculator be used for different sample types?
A: Yes, the formula applies to various sample types including water, food, clinical specimens, and environmental samples.

Q5: What if I have multiple dilution plates with countable colonies?
A: Use the plate with colonies between 30-300. If multiple plates are in range, average the results from appropriate dilutions.