Quick facts
- Chocolate agar is blood agar that has been heated until the red cells burst, releasing factor V (NAD) and factor X (haem) into the medium; the colour comes from the lysed blood, not from cocoa.
- In the United States an enriched medium of this kind is a named Class I entry at 21 CFR 866.2330.
- Plain blood agar is filed separately at 21 CFR 866.2320, and a general-purpose plate such as tryptic soy agar at 21 CFR 866.2300, all Class I.
- In Canada a general-purpose or enriched culture medium is a Class I in-vitro diagnostic device under the Medical Devices Regulations.
- The performance of the plate is set by a standard rather than by the class: ISO 11133 covers preparation and performance testing, and CLSI M22 covers quality control of commercially prepared media.
- The entries and rule text quoted here were checked against the openFDA device classification API and the Regulations on 2026-10-06.
A chocolate agar plate is a brown, opaque medium used to grow organisms that will not grow on an ordinary blood plate. It is used in a clinical microbiology laboratory to recover Haemophilus influenzae, Neisseria species and other fastidious organisms from a respiratory or genital specimen. The plate is enriched rather than selective, and that single fact decides which rulebook entry it sits under.
Why is it called chocolate agar if there is no chocolate in it?
Because of the colour, not the content. The medium starts as a blood agar base, and it is heated until the red cells lyse. Lysis releases two growth factors that the intact red cell keeps inside: factor V, or NAD, and factor X, or haem. The released haem gives the medium its brown colour, which is where the name comes from.
That heating step is what makes the plate enriched. A plain blood plate already contains the same blood, but the factors stay locked inside the cells, so an organism that cannot lyse them will not grow. Heating the base first is the whole reason chocolate agar can support organisms that blood agar cannot.
How do Canada and the United States classify the medium?
The two countries reach the same class from different directions, and the entry depends on the medium rather than on the plate.
| Medium | Canada | United States |
|---|---|---|
| Chocolate agar (enriched) | Class I in-vitro diagnostic device | Class I, 21 CFR 866.2330 |
| Blood agar (non-selective, differential) | Class I | Class I, 21 CFR 866.2320 |
| Tryptic soy agar (general purpose) | Class I | Class I, 21 CFR 866.2300 |
| Medium supplement | Class I | Class I, 21 CFR 866.2450 |
| Basis of the class | General-purpose medium, low individual risk | The named entry it is filed under |
In the United States each medium is a named Class I entry, and a product filed under that entry reaches the market without premarket notification where the entry is exempt. In Canada a general-purpose or enriched culture medium is a Class I in-vitro diagnostic device, and a Class I device is not licensed device by device; the manufacturer keeps an establishment licence and the records the Regulations require.
The distinction that matters to a buyer is between the medium and the plate format. The same enriched base supplied in a 90 mm dish, in a tube, or as a dehydrated powder is the same entry; a plate that also carries an antimicrobial can move to a different class, because the selective agent changes what the medium is for.
Which organism is chocolate agar used for?
The medium is chosen for the organism, and the quality-control organism follows the choice.
| Medium | Typical target | Quality-control organism |
|---|---|---|
| Chocolate agar | Haemophilus influenzae, Neisseria species | H. influenzae, N. gonorrhoeae |
| Blood agar | Streptococcus, general recovery | S. pyogenes, S. pneumoniae |
| Tryptic soy agar | Environmental monitoring, bioburden | S. aureus, B. subtilis |
| MacConkey agar | Gram-negative bacilli, lactose | E. coli, P. aeruginosa |
Read together, the four rows show why a laboratory cannot swap one plate for another without rethinking the quality control. A plate that grows the wrong control organism is not a plate that has been checked, and the check is what a reviewer looks for first.
Which standard decides whether the plate performs?
The plate's performance is a standard question rather than a class question. ISO 11133 sets out how a culture medium is prepared, produced and performance-tested, including the productivity and selectivity checks. CLSI M22 covers quality control of commercially prepared microbiological culture media, and CLSI M100 carries the antimicrobial susceptibility tables that a laboratory reads alongside the plate.
For a laboratory the practical step is to keep the certificate of analysis with the lot, and to record the quality-control organism and the outcome on receipt. That record is what turns a plate into a traceable item when a result is questioned.
What do the two rulebooks actually say?
The entries are short, and the difference between them is the point of this article.
| Entry | Wording in the source | Effect on a chocolate agar plate |
|---|---|---|
| 21 CFR 866.2330, US | Culture media, enriched | Named Class I entry |
| 21 CFR 866.2320, US | Culture media, non-selective and differential | Blood agar, Class I |
| 21 CFR 866.2300, US | Culture media, non-selective and non-differential | General-purpose plate, Class I |
| 21 CFR 866.2450, US | Supplement, culture media | Class I supplement |
| MDR section 45, Canada | An establishment licence for the activity | Who may import or sell |
Read together, the five lines explain why a supplier cannot move the class by relabelling a plate. A chocolate plate described as a general-purpose plate while it is enriched is described against the text, not against the label.
Which consumables does a microbiology bench restock?
A culture bench runs on the same supplies as any other bench. The double-tipped cotton swabs are the collection item used before a plate is streaked, and the sterile graduated specimen cups carry the sample into the bench area. A laboratory that also monitors its own steriliser pairs the sterilization monitoring collection with the 24-hour monitoring five-pack trial. Laboratories and multi-site groups ordering at case level use the wholesale ordering page, and the B2B wholesale collection lists the lines held for institutional buyers. Reselling? become a distributor.
How is a chocolate plate stored and handled?
An enriched plate is more sensitive than a general-purpose one, so the handling rules matter. The plate is warmed to room temperature before it is inoculated, because a cold plate can shock a fastidious organism and suppress the growth the medium was chosen to support. The plate is used the same day it is brought to the bench, and it is not left open on the bench while other work is done.
Storage follows the same logic. A prepared plate is kept in the dark at the temperature the manufacturer states, and it is not used past the expiry on the lot. A plate that has dried out, or one that has stood on a warm bench for hours, will not give the growth the certificate of analysis describes, and a result read from it is read against the wrong baseline.
The two habits together decide whether the enriched medium delivers what it promises. A plate warmed correctly and used the same day supports the organism; a plate handled carelessly gives a weak or absent growth that looks like a negative result rather than a handling problem. Recording the time the plate left the refrigerator is a simple way to tell the two apart after the fact, and the record costs nothing to keep.
Sources
- 21 CFR 866.2330, Culture media, enriched
- 21 CFR 866.2320, Culture media, non-selective and differential
- 21 CFR 866.2300, Culture media, non-selective and non-differential
- 21 CFR 866.2450, Supplement, culture media
- Medical Devices Regulations, SOR/98-282, full text
- openFDA device classification API
- ISO 11133:2014, preparation of culture media
- CLSI M22, quality control of commercially prepared culture media
- CLSI M100, performance standards for antimicrobial susceptibility testing
- ISO 13485:2016, medical devices quality management
- ISO 14971:2019, risk management for medical devices
- Health Canada, medical devices guidance
- Public Health Ontario, laboratory services test index
- USP, general chapter 1116, microbiological control
- CLSI, clinical and laboratory standards
- Standards Council of Canada
- CCOHS, OSH answers
- Canadian Dental Association
A count of how many plates a bench opens is a count that is hard to rebuild later. The printable media receipt and lot log is a blank form with columns for the medium, the lot, the date received and the control organism, so a failing lot is visible on the day. The media log generator on the same page sizes the form to the number of benches a laboratory runs. No account and no sign-up are needed to open either one.
Every microbiology setup is different. Ask a compliance specialist and you will get a written answer specific to your equipment and province, with the regulation or standard it is based on cited.
Related reading
- Blood Culture Bottles in Canada vs the US: Which Rules Apply?
- Microcentrifuge Tubes in Canada vs the US: Which Standards?
- Microscope Slides in Canada vs the US: Which Size and Finish?
CliniEco Medical supplies eye care, laboratory and dental consumables of the kind described in this article. MDEL #35334. This article is written for optometry, laboratory and procurement professionals and is not legal advice; the class of a device and the records kept by a clinic belong to the manufacturer and to the requirements that apply to it.
Frequently Asked Questions
Does chocolate agar contain chocolate?
No. The name comes from the brown colour of the medium, which is produced by heating blood agar until the red cells lyse.
What does heating the blood do?
It releases factor V, or NAD, and factor X, or haem, from inside the red cells. Those two factors let the medium support organisms such as Haemophilus influenzae that will not grow on a plain blood plate.
How is chocolate agar classified in the United States?
It is an enriched medium and is filed as a Class I entry at 21 CFR 866.2330.
Is blood agar the same entry?
No. Blood agar is a non-selective, differential medium and is filed at 21 CFR 866.2320, which is a separate Class I entry.
How does Canada classify the same medium?
In Canada a general-purpose or enriched culture medium is a Class I in-vitro diagnostic device, and a Class I device sits under an establishment licence and records rather than a device licence.
Which standard decides the plate's performance?
ISO 11133 covers the preparation and performance testing of a culture medium, and CLSI M22 covers the quality control of commercially prepared microbiological media.
Which quality-control organism is used for a chocolate plate?
A chocolate plate is checked with an organism that needs the enriched factors, such as Haemophilus influenzae or Neisseria gonorrhoeae, rather than with the organism used on a general-purpose plate.
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