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USP Microbial Limits Testing

For experienced testing of raw materials and other nonsterile products in pharmaceutical manufacturing, turn to Microtest. We offer excellent solutions for USP Microbial Limits Testing (MLT).

The Quantitative phase of testing determines the bioburden of given pharmaceutical manufacturing samples, determining the number of total aerobic organisms as well as the total number of yeasts, and molds.

The qualitative phase of testing examines samples per U.S. FDA criteria for “objectionable organisms.” For minimum coverage, these criteria require testing for the following:

  • The bacteria Escherichia coli (E. coli)
  • The bacteria Staphylococcus auseus (S. auseus)
  • The yeast Candida albicans (C. albicans)
  • The bacteria Pseudomonas aeruginosa (Ps. aeruginosa)
  • The fungus Aspergillus niger (A. niger)

The first step in Microbial limits testing is the preparatory testing which validates the product with the method used. This ensures the product has no inhibitory effect on the recovery of organisms from the product. Once the product has passed the Preparatory Test, the product is validated for routine screening. The routine Microbial limits screening test consists of the total aerobic and total yeast and mold counts as well as the test for objectionable microorganisms. If the total aerobic and total yeast and mold counts are acceptable and no objectionable organisms are found, Microtest then gives the “go-ahead” for swift release of the product or raw material.

Full microbial limits testing then inoculates specific organisms into general nutrient media. After allowing time for any growth, our microbiologists transfer the results to specific media that show differential reactions (usually via color changes) to the presence of a given organism.

The Preparatory and the routine microbial limits screening test can be particularly problematic for inexperienced laboratory personnel. With an average of more than 10 years’ experience, Microtest specialists bring the industry’s highest levels of expertise to the task.