Quick facts
- United States: a differential culture medium has a named entry at 21 CFR 866.2320, described as a device that "consists primarily of liquid biological materials intended for medical purposes to cultivate and identify different types of pathogenic microorganisms".
- United States: section 866.2320(b) places the medium in Class I (general controls) and exempts it from premarket notification subject to 866.9.
- United States: a transport culture medium is a separate entry at 21 CFR 866.2390, defined as "a semisolid, usually non-nutrient, medium that maintains the viability of suspected pathogens contained in patient specimens while in transit".
- United States: a microbiological incubator is reached through 21 CFR 866.2540, also Class I, and supplements added to a basal medium are covered by 21 CFR 866.2450.
- Canada: Schedule 1 to the Medical Devices Regulations, SOR/98-282 names no culture medium, so the class is reached through the general rules for a non-invasive device.
- Both countries: the material specification for the plates is narrower than the catalogue suggests, because ISO 13132:2011 sets requirements for glass Petri dishes and its scope does not extend to the plastic plates most laboratories now use.
A culture medium is a powder that becomes a plate, a slope, a tube or a bottle, and the same powder can be sold under four different descriptions. The descriptions matter more than the powder because the American framework classifies by intended use, and one of the entries answers a question a catalogue usually does not: whether the medium is meant to grow organisms or only to keep them alive until the laboratory sees them.
Is culture medium a Class I device in the United States?
Yes, and the entries are written by function rather than by product name, which is why a differential medium and a transport medium are two sections rather than one.
The differential entry, 866.2320, describes a medium that identifies "different types of pathogenic microorganisms" by "the addition of a specific biochemical component", with the organism identified by "a visible change (e.g., a color change)". The class is Class I, with a premarket notification exemption.
The transport entry, 866.2390, describes a medium that "maintains the viability of suspected pathogens contained in patient specimens while in transit from the specimen collection area to the laboratory". This is the sentence a catalogue should carry and often does not: a transport medium is not a growth medium, and the entry says so by calling it "semisolid, usually non-nutrient". A swab transport kit that is described as a culture medium is being described in the wrong vocabulary.
A supplement is the third entry. Section 866.2450 covers "a device, such as a vitamin or sugar mixture, that is added to a solid or liquid basal culture medium to produce a desired formulation", intended to "enhance the growth of fastidious microorganisms". A laboratory that adds a supplement to a base medium has made a formulation from two devices.
Canada reaches the same products through the general rules. A prepared plate is a non-invasive device that does not penetrate the body, so the general non-invasive rule applies, and the class follows the rule rather than a named entry. The function described in the product name does not change the route.
| Item | Canada | United States |
|---|---|---|
| Named entry for a differential medium | None in Schedule 1 | 866.2320, Class I |
| Named entry for a transport medium | None | 866.2390, Class I |
| Named entry for a supplement | None | 866.2450, Class I |
| Named entry for an incubator | None | 866.2540, Class I |
| Route to the class | Non-invasive device under the general rules | The entry states the class |
Does the American definition of transport medium exclude a growth medium?
Yes, expressly, and this is the distinction most often blurred in a catalogue.
The two definitions separate on three words. A differential medium is described as having "liquid biological materials" that identify organisms by a biochemical reaction and a visible change. A transport medium is described as "semisolid, usually non-nutrient" and as maintaining viability "while in transit". One grows and differentiates, and the other preserves.
A buyer reading a specification sheet can use that split. A product marketed as a transport device should state the semisolid, non-nutrient character of the medium and the transport role, and a product marketed as a differential device should state the indicator system and the colour change that reports the reaction. A sheet that claims both roles for one product is describing two devices.
Canada does not write a matching pair of definitions, so a Canadian file records the intended use and the rule path instead. The distinction still matters operationally, because a medium chosen to grow an organism and a medium chosen to carry it answer different questions.
| Question | Canada | United States |
|---|---|---|
| Where the definition lives | General rules, no named entry | 866.2320 and 866.2390 |
| Growth and differentiation | Described by intended use | Liquid biological materials with a biochemical indicator |
| Transport and preservation | Described by intended use | Semisolid, usually non-nutrient, maintains viability in transit |
| Effect on the class | None; Class I either way | None; Class I either way |
| Why the split matters | Specification and record | Specification and record |
Does the plate standard cover plastic plates?
No, and a laboratory that assumes it does has a gap in its specification file.
ISO 13132:2011 sets out "requirements and tests for glass Petri dishes intended for general laboratory purposes and microbiological work". The material is named in the title, so the standard's requirements and tests are written for glass. A polystyrene plate, which is what most laboratories now pour or buy, sits outside that scope, and its specification has to come from the manufacturer's stated dimensions and the laboratory's own verification.
That is a gap worth recording explicitly. A file that cites the Petri dish standard for a plastic plate is citing a document that does not cover the product. The stronger record states the nominal dimensions, the material, the sterility claim and the supplier's certificate, and cites the standard only where glass is used.
The quality assurance side of the medium itself sits in ISO 11133:2014, which covers "all categories of culture media prepared for use in laboratories performing microbiological analyses". A laboratory that documents medium preparation under that standard and plates under a supplier certificate has covered both halves.
Which media types are differential, selective or both?
The labels overlap, and the entry that matters is the one that names the mechanism.
- Differential media report a reaction by a visible change, which is the mechanism the American entry describes. A medium that turns a colony a different colour is differential.
- Selective media suppress some organisms so that others can be seen. Selectivity is a property of the formulation rather than a separate device class.
- Enriched media carry added nutrients for organisms with complex requirements, which is what the supplement entry at 866.2450 is built to describe.
- Transport media preserve rather than grow, which is the distinction the transport entry draws.
- Chromogenic media make the indicator visible as colour, so they are differential media with a designed indicator rather than a separate type.
A specification sheet is clearer when it names which of these five roles a product fills, because the roles map to the regulation entries.
What has to be recorded for a prepared plate?
Six records, and the two that most often go missing are the formulation and the incubation conditions.
- The medium and its formulation. The base medium and any supplement recorded separately, since a supplement is a device in its own right.
- The batch and expiry. Recorded per pour or per lot, because the expiry belongs to the prepared plate and not to the powder.
- The plate specification. Nominal diameter and material, with the standard cited only where the plate is glass.
- The sterility claim. The form in which sterility is represented, kept with the batch record.
- The incubation conditions. Temperature and time, recorded because the reading depends on them and because the incubator is itself a regulated device.
- The reading method. Colony count or colour change, recorded so the result can be reproduced.
Which consumables does a media bench restock?
A media bench consumes plates, swabs and transport packaging on one cycle, and a laboratory that pours its own plates adds the incubator to the same order. For clinics and multi-site groups buying at case level, the wholesale ordering page sets out account and case terms, and the B2B wholesale collection lists the lines held for institutional buyers. The sterile Petri dishes cover the plates, the cotton swabs cover sampling and bench work, and the 24-hour biological indicator incubator covers the temperature step. A site moving to in-house spore monitoring can start with the biological indicator 5-pack trial.
Sources
- 21 CFR 866.2320, differential culture medium
- 21 CFR 866.2390, transport culture medium
- 21 CFR 866.2450, supplement for culture media
- 21 CFR 866.2540, microbiological incubator
- 21 CFR 864.4010, general purpose reagent
- Medical Devices Regulations, SOR/98-282, full text and Schedule 1
- ISO 11133:2014, culture media quality assurance
- ISO 13132:2011, glass Petri dishes
- ISO 15189:2022, medical laboratories
- ISO 13485:2016, medical device quality management systems
- ISO 14971:2019, risk management of medical devices
- Public Health Ontario, specimen acceptance criteria
- Public Health Ontario, laboratory services test index
- CLSI, microbiology standards
- Health Canada, medical devices
- Health Canada, drug and health product portal
- openFDA device classification API
- World Health Organization, laboratory biosafety manual
- CCOHS, OSH answers
- College of Medical Laboratory Technologists of Ontario
A prepared plate is only as good as the record under it. The printable media batch log is a free sheet with a row per pour and a column for the supplement, so a base medium and an additive never share one field. The generator sized to a media bench builds the sheet from the number of plates a laboratory pours and the media it holds, which keeps a clinic bench from being handed a reference-laboratory form. No account and no sign-up are needed to open either one.
Where the role of a medium or the scope of a plate standard needs to be explained for an audit, the written answer is the one worth having. Ask a compliance specialist and a written answer comes back specific to your equipment and province, with the regulation or standard it is based on cited.
Related reading
- Blood Agar in Canada vs the US: Which Media Rules
- Agar Plates in Canada vs the US: Which Media Standard
- Microbiology Culture Swabs: Types and Transport for Canadian Labs
CliniEco Medical supplies laboratory, eye care and dental consumables of the kind described in this article. MDEL #35334. This article is written for laboratory, microbiology and procurement professionals and is not safety or regulatory guidance; the choice of medium and the records kept by a laboratory belong to its quality system and to the requirements that apply to it.
Frequently Asked Questions
Is culture medium a Class I device in the United States?
Yes. The differential culture medium at section 866.2320, the transport culture medium at section 866.2390 and the supplement at section 866.2450 are all placed in Class I, general controls.
What is the difference between differential and transport culture medium?
A differential medium grows and identifies organisms by a biochemical reaction that produces a visible change. A transport medium is described as semisolid and usually non-nutrient, and its role is to maintain the viability of suspected pathogens while the specimen travels to the laboratory.
Does ISO 13132 cover plastic Petri dishes?
No. The standard is titled for glass Petri dishes, and its requirements and tests are written for that material, so a polystyrene plate sits outside its scope and must be specified from the manufacturer's stated dimensions and the laboratory's verification.
Is a supplement a separate device from the base medium?
Yes. Section 866.2450 treats a supplement, such as a vitamin or sugar mixture, as a device of its own, added to a basal medium to produce a desired formulation. A record that keeps the base and the supplement on separate lines reflects that.
Is a microbiological incubator regulated?
Yes, in the United States it is a named entry at section 866.2540, placed in Class I with a premarket notification exemption and a quality system carve-out for devices not represented as sterile.
Which records should a media batch keep?
Keep the base medium and any supplement separately, the batch and expiry of the prepared plate, the plate dimensions and material, the sterility claim, the incubation temperature and time, and the reading method.
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