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Quality reference

Sterility, Endotoxin, and Mycoplasma Testing

Reviewed by ExaVeyra Sciences editorial team · Updated 29 August 2026

Sterility, endotoxin and mycoplasma are usually presented together, as though they were three ways of saying the same thing. They are not. They answer three different questions, they fail in three different ways, and a preparation can pass one while the others were never run.

Knowing which question each one answers is what turns a row of passes on a certificate into information you can act on.

Sterility asks whether anything is alive

A sterility test incubates the material in growth media and looks for organisms multiplying. The federal requirement for biological products sits in 21 CFR 610.12, and the compendial method most laboratories run against is USP Chapter 71.

Its blind spot is time and its blind spot is scale. The test takes days to read out, and it examines a sample rather than the batch, so a pass is a statement about what grew from what was tested.

Endotoxin asks what dead bacteria left behind

Endotoxin is a fragment of the outer membrane of gram-negative bacteria. It is heat stable, it survives processes that kill the organism, and it provokes a response in a patient at quantities far below anything a sterility test would notice.

That is why the two tests are not redundant. A preparation can be genuinely sterile and still carry endotoxin, because the bacteria that produced it are gone and the residue is not.

Mycoplasma asks about the organisms the other tests miss

Mycoplasma are very small bacteria with no cell wall. They pass through filters that retain other organisms, they do not reliably grow in standard sterility media, and they can persist in a cell culture without turning it visibly cloudy.

For anything derived from cultured cells, that makes mycoplasma its own test rather than a subset of sterility. A sterility pass is not evidence of mycoplasma absence.

What sits alongside the contamination panel

A contamination panel is one of four things a complete package carries, and knowing what the other three are makes it straightforward to ask for the set rather than assembling it a question at a time.

  • Identity and characterisation, which establish what the material is. Covered in the marker panel and particle counting references.
  • Lot traceability, so the certificate in your file names the lot on the container in front of you.
  • Storage and handling conditions, which govern the material from release to the treatment room.
  • The test list itself, since an attribute that was assayed can be judged and one that was not can be requested.

Together those four cover what a purchasing decision needs. A supplier holding all of them can send the set in a business day, because they are already assembled for their own quality system.

What to ask for, in one line each

TestAsk forWhy
SterilityThe method, the lot, and the incubation period.A pass is a statement about a sample under a method, not about the batch in the abstract.
EndotoxinThe measured value in endotoxin units, and the limit applied."Pass" without a number cannot be compared between two suppliers or against your own threshold.
MycoplasmaWhether it was run at all, and by what method.It is the one most often absent from a panel, and a sterility result does not substitute for it.

A supplier who answers all three in numbers has a quality system behind the certificate. One who answers in passes has a document.

How to get the release data

Release testing exists before anything ships, so the results are already written down. Asking for measured values rather than passes is a request for what the laboratory already produced.

ExaVeyra releases lot-specific sterility and contamination data with its certificates to NPI-verified practices, which is the same step that opens wholesale pricing and the pharmacy formulary.

Sources

  1. 21 CFR 610.12, Sterility (accessed 29 August 2026)
  2. 21 CFR Part 610, General Biological Products Standards (accessed 29 August 2026)

Scientific literature

Each source carries the kind of study it was and, where the study enrolled people, how many. Study design decides what a result can establish, so it is stated rather than left to be inferred. Each line also says what that source is carrying on this page.

  1. Marton C, Clémenceau B, Dachy G, et al. Harmonisation of quality control tests for academic production of CAR-T cells: a position paper from the WP-bioproduction of the UNITC consortium. Bone Marrow Transplantation, 2025. doi:10.1038/s41409-025-02637-8 PMID:40442256Consensus statementSource 1 supports: A consortium position on which release tests belong on a cell-derived product and why. Cited because it treats sterility, endotoxin and mycoplasma as three separate release questions rather than one, which is the argument of this page.
  2. Andriolo G, Provasi E, Brambilla A, et al. GMP-grade methods for cardiac progenitor cells: cell bank production and quality control. Methods in Molecular Biology, 2021. doi:10.1007/7651_2020_286 PMID:33381854Narrative reviewSource 2 supports: A worked quality-control protocol for a cell-derived product, including where mycoplasma testing sits relative to sterility. Cited as an example of what a real release panel contains rather than as evidence about any product.
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Common questions

If a preparation passed sterility, why does endotoxin matter?
Because endotoxin is not an organism. It is a heat-stable fragment of the outer membrane of gram-negative bacteria, so it persists after the bacteria that produced it are dead and gone. A sterility test looks for something alive and would not detect it.
Is mycoplasma testing standard on an exosome certificate?
It is the one most often missing. Mycoplasma are small, lack a cell wall, pass through filters that retain other organisms and do not reliably grow in standard sterility media, so they need their own assay. For material derived from cultured cells it is worth asking about specifically.
What endotoxin limit should we expect to see?
That depends on the route and the quantity administered, which is a prescriber determination rather than something a supplier sets for you. What matters at the purchasing stage is that a measured value and the limit applied both appear on the certificate, so the result can be judged rather than accepted.
Does a pass on all three mean the material is safe to use?
No. It means three specific contamination questions were asked and answered on the sample tested. Identity, potency, handling after receipt and suitability for a given patient are all outside what these assays establish.

Related reading

Cold chain validation and storageMISEV2023 and supplier documentationQualifying a supplier before the first orderExosome CMC requirementsHow to evaluate an exosome supplier COA

These statements have not been evaluated by the FDA. This product is not intended to diagnose, treat, cure, or prevent any disease. There are no FDA-approved exosome products. Biomolecular signaling vesicle products distributed by ExaVeyra Sciences are supplied for topical aesthetic treatments in clinics and for medical, molecular biology, and biochemistry research applications, and are not tissue products as defined by FDA guidelines.

This guide summarizes publicly available federal regulation for licensed practitioner education. It is for informational purposes only, it is not legal advice, medical advice, or regulatory guidance, and it does not establish that any particular product or practice is compliant. Regulation changes, and state requirements frequently differ from the federal floor. Consult a healthcare attorney licensed in your jurisdiction and your own state boards before acting on anything here.