Microbiological Examination of Nonsterile Products: USP (61), (62)

Clients are advised to review the status of their non-sterile product testing in light of the new USP changes. If your substances or products have been validated and tested using USP methods other than those provided in USP 35-NF 30 it is essential to re-validate and begin testing using USP 35-NF 30 tests. Many of the changes are designed to harmonize with the European Pharmacopeia methods. The new USP methods now include more organisms. These are major changes for microbial limits testing. Clients are advised to factor these new USP methods into their testing schedules.

USP Microbiological Examination of Nonsterile Products: Microbial Enumeration Tests

USP tests allow quantitative enumeration of mesophilic bacteria and fungi that may grow under aerobic conditions. The tests are designed primarily to determine whether a substance or preparation complies with an established specification for microbiological quality.

USP Microbiological Examination of Nonsterile Products: Tests for Specified Organisms

USP tests allow determination of the absence of, or limited occurrence of, specified microorganisms that may be detected under USP testing conditions.

The following is a summary of the changes to USP.

  • USP microbial enumeration tests include changes in pass/fail criteria and includes longer incubation durations than in previous editions.
  • The Preparatory Test is replaced by the Method Suitability for product inhibition. The growth promotion organisms and the methodology have been significantly updated to include more types of organisms and different growth media. The performance of the Suitability Test Method ensures that any antimicrobial activity inherent in the sample to be tested does not adversely affect the reliability of the test and that the test procedure to be routinely utilized is otherwise suitable for use with the sample.
  • The tests for specified microorganisms are included in USP.
  • More organisms have been specified for USP testing. Organisms such as Candida albicans, Clostridia species and bile-tolerant gram-negative bacteria may be required to be tested depending on specifications regarding product formulation.
  • Clients must now specify which microorganisms are required to be absent from their substances or products. This requirement is based on the unique characteristics of the product’s formulation process, raw materials, etc.

The USP 61/62 test utilizes the Compendial Method, as set forth by USP, for the testing of non-sterile pharmaceutical products and other non-sterile article for bacterial load and pathogenic organisms. USP 61 testing includes a plate count and suitability testing, which validates the plate count. USP 62 testing evaluates the presence or absence of objectionable organisms. This test method has defined procedures for the detection of Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Salmonella species, fungal organisms and a quantitative MPN for Bile Tolerant Gram Negative bacteria. USP 61/62 testing is recommended for all pharmaceutical raw materials, non-sterile products, liquids and powders, transdermal patches and dietary supplements.

The USP tests are designed to validate and determine the quantitation of organisms present and screen for the presence or absence of objectionable organisms in non-sterile pharmaceutical products.

The validation and suitability testing are performed once for each product. The testing verifies the validity of the testing method by demonstrating any antimicrobial properties of the product do not inhibit possible recovery of growth. Both validation and suitability are performed with inoculation of the product which describes the validation of the plate count preparation tests and plating method by demonstrating recovery of Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus subtilis, Candida albicans and Aspergillus brasiliensis on the appropriate media. USP suitability testing verifies the validity of the testing method by demonstrating the recovery of Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, bile-tolerant gram-negative bacteria, Clostridia species, Salmonella species and Candida albicans.

USP routine analysis is performed to determine the total aerobic microbial and total yeasts and molds counts. The plating of the sample can be performed by membrane filtration, pour plating, or the spread plate method. The sample is diluted in an appropriate medium, generally Phosphate Buffer Solution, then it is plated on Soybean Casein Digest Agar (SCDA) for total aerobic microbial count (TAMC), and Sabaroud Dextrose Agar (SDEX) for total yeasts and molds count (TYMC). Incubation is for 3-5 days at 30-35°C for TAMC and 5-7 days at 20-25°C for TYMC.

USP routine tests for the determination of the presence of specified microorganisms; Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, bile-tolerant gram-negative bacteria, Clostridia species, Salmonella species and Candida albicans. The test involves an initial enrichment of the sample in Soybean Casein Digest Broth (SCDA) or other appropriate neutralizing media, and then streaking the enriched sample onto selective agars for determination of the presence of the defined objectionable organisms.

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