Quick answer
USP 61 is the microbial enumeration test for nonsterile products: it counts total aerobic microbes (TAMC) and total yeasts and molds (TYMC). USP 62 tests for the absence of specified organisms such as E. coli and Salmonella. USP 2021 and 2022 are the dietary supplement versions, and acceptance criteria are in USP 1111 for drugs and USP 2023 for supplements.
What does each USP microbiology chapter cover?
USP chapters for nonsterile products. Titles as shown in USP's public chapter previews (year of the version in brackets); scope as described in those previews and in FDA's Q4B Annex 4C guidance.
| Chapter | Title | What it does |
|---|---|---|
| USP <61> | Microbiological Examination of Nonsterile Products: Microbial Enumeration Tests (2024) | Counts mesophilic bacteria and fungi that grow under aerobic conditions (TAMC and TYMC) |
| USP <62> | Microbiological Examination of Nonsterile Products: Tests for Specified Microorganisms (2026) | Shows the absence, or limited occurrence, of named organisms |
| USP <1111> | Microbiological Examination of Nonsterile Products: Acceptance Criteria for Pharmaceutical Preparations and Substances for Pharmaceutical Use | Acceptance criteria for nonsterile drug products and substances, harmonized internationally |
| USP <2021> | Microbial Enumeration Tests, Dietary Ingredients and Dietary Supplements (2025) | Estimates the number of viable aerobic microorganisms in dietary ingredients and supplements |
| USP <2022> | Microbiological Procedures for Absence of Specified Microorganisms, Dietary Ingredients and Dietary Supplements (2025) | Tests supplements for objectionable organisms that should be absent |
| USP <2023> | Microbiological Attributes of Nonsterile Nutritional and Dietary Supplements (2025) | Discusses the microbial quality of supplements and their ingredients and how specifications are set |
The 2025 versions of <2021> and <2022> say "Dietary Ingredients and Dietary Supplements" in their titles; earlier versions said "Nutritional and Dietary Supplements". The drug chapters (<61>, <62>, <1111>) are harmonized with the European and Japanese pharmacopoeias. The supplement chapters (<2021>, <2022>, <2023>) are not among the harmonized texts.
What do TAMC and TYMC mean in USP 61?
TAMC is the total aerobic microbial count, and TYMC is the total combined yeasts and molds count. Under the harmonized enumeration text, TAMC is the number of colony-forming units (CFU) on casein soya bean digest agar, and any fungi that grow there count toward it. TYMC is the CFU count on Sabouraud dextrose agar, and any bacteria that grow there count toward TYMC. Results are given per gram or per milliliter.
The text allows membrane filtration or plate-count methods. The most-probable-number method is the least accurate and is kept for situations such as very low bioburden. Before routine use, the method has to be shown suitable for the product, because some products have antimicrobial activity that must be neutralized or removed. Validated alternative or automated methods may be used if equivalence is shown.
One limit matters for supplements: the harmonized text says the enumeration methods are not applicable to products containing viable microorganisms as active ingredients, so probiotic products need a specification written around that.
Which specified organisms does USP 62 test for?
The harmonized text for tests for specified microorganisms covers seven:
- Bile-tolerant gram-negative bacteria
- Escherichia coli
- Salmonella
- Pseudomonas aeruginosa
- Staphylococcus aureus
- Clostridia
- Candida albicans
A product is not tested for all seven by default. The acceptance criteria, or your specification, name which organisms apply and in what amount of product, for example "absence of E. coli in 1 g". For supplements, USP <2022> starts from the GMP principle that objectionable organisms must be absent, where an organism is objectionable if it is a potential health hazard to someone using the product as directed or if it can grow in the product.
What are the harmonized acceptance criteria for nonsterile drug products?
The harmonized acceptance criteria (USP <1111>, Ph. Eur. 5.1.4 and the Japanese Pharmacopoeia text) are public through the Japanese Pharmacopoeia, 18th edition, English version, published by Japan's Ministry of Health, Labour and Welfare (General Information G4-1-170), which states the chapter is harmonized with the USP and Ph. Eur. FDA's Q4B Annex 4C guidance recognizes the three texts as interchangeable.
Harmonized acceptance criteria for nonsterile dosage forms and substances (selected rows). Source: harmonized text USP <1111> / Ph. Eur. 5.1.4 / JP, recognized as interchangeable in FDA Q4B Annex 4C(R1).
| Product type | TAMC (CFU/g or CFU/mL) | TYMC (CFU/g or CFU/mL) | Specified microorganisms |
|---|---|---|---|
| Non-aqueous preparations for oral use | 10³ | 10² | Absence of E. coli (1 g or 1 mL) |
| Aqueous preparations for oral use | 10² | 10¹ | Absence of E. coli (1 g or 1 mL) |
| Rectal use | 10³ | 10² | None listed |
| Oromucosal, gingival, cutaneous, nasal and auricular use | 10² | 10¹ | Absence of S. aureus (1 g or 1 mL); absence of P. aeruginosa (1 g or 1 mL) |
| Substances for pharmaceutical use | 10³ | 10² | Not set in this table |
Figures checked against the sources below on 3 November 2026; rules change, so confirm the current version before relying on them.
Criteria are read with a built-in allowance: 10¹ CFU means a maximum acceptable count of 20, 10² means 200, and 10³ means 2,000. The organism list is not exhaustive, and the USP and Ph. Eur. versions can add text that is not harmonized, so check the chapter your specification cites.
What microbial limits apply to dietary supplements?
The table above is for drug products. For supplements, the USP chapter is <2023>, which discusses microbial attributes of nonsterile supplements and the ingredients they are made from, from synthesized vitamins to plant extracts and animal byproducts. The numeric tables are published in the subscription USP-NF; check the current chapter, or the figures your buyer quotes, before relying on a number.
Under 21 CFR 111.70, a supplement manufacturer must set limits on the types of contamination that may adulterate each finished batch, and on components. USP <2023> is the USP chapter written for those limits in supplements, and a buyer's specification may be stricter. See 21 CFR 111 testing requirements for the wider Part 111 picture.
How do you use these chapters with your CoA?
- Find the chapter your specification cites: <61>/<62> with <1111> for drug products, or <2021>/<2022> with <2023> for supplements.
- Compare each count on the CoA with the matching criterion, using the 20/200/2,000 reading where a limit is a power of ten.
- Check each specified organism is reported for the amount of product the criterion names (1 g, 10 g).
- Note results reported as less than a value: the value is the lowest count the method could report for that sample.
Verified Analytical Laboratory's microbiology testing page lists the counts and organisms it reports. Send your specification and the chapter it names with the sample, and we confirm the method and sample amount with your quote.
Questions about this page
What is the difference between USP 61 and USP 62?
What does a limit of 10³ CFU/g mean?
Can USP 61 be used to test probiotics?
Is USP 1111 the same as USP 2023?
Does 21 CFR 111 require USP 2021 and 2022 testing?
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