Microbial Limit Test (MLT) Calculator
Calculate Bioburden, Pass/Fail Status & Dilution Requirements (USP <61>)
1. Sample Preparation
CFU/g or mL
g or mL
mL (pH 7.2 Buff)
2. Plating Details
Select Level
TEST RESULTS
Total Dilution Factor:
0
Mean Count per Plate:
0 CFU
Calculated Result:
0 CFU/g
Pass/Fail Status (USP Criteria):
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Smart Dilution Recommendation
Based on your limit, verify the recommended dilution here.
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Understanding USP <61> Microbial Limit Testing
The Microbial Limit Test (MLT) evaluates the bioburden of non-sterile pharmaceutical products. It includes the Total Aerobic Microbial Count (TAMC) and Total Combined Yeasts and Molds Count (TYMC).
1
Preparation: The sample is typically prepared by dissolving or suspending 10g of product in 90mL of diluent (e.g., Soybean-Casein Digest Broth), resulting in a 1:10 dilution.
2
Plating: The prepared sample is then serially diluted ($10^{-1}, 10^{-2}$, etc.) and plated on Agar medium.
3
Acceptance Criteria (The 2x Rule): USP <61> states that a limit of $10^2$ CFU/g is interpreted as a maximum acceptable count of 200 CFU/g.
- Limit 10 CFU/g → Max 20 CFU/g
- Limit 100 CFU/g → Max 200 CFU/g
- Limit 1000 CFU/g → Max 2000 CFU/g
Calculation Formula
Result (CFU/g) = Mean Count × Dilution Factor
Dilution Factor = (Sample Wt + Diluent Vol) / Sample Wt × Serial Dilution