What a sterility test answers
Whether anything in the sample is alive and able to grow. A sterility test does not look for contamination directly: it gives any organism present the conditions to multiply, then watches for growth.
How we run it
Under the pharmacopeial method (USP <71>, harmonized with Ph. Eur. 2.6.1) the sample goes into two growth media. Fluid thioglycollate medium is incubated at 30–35 °C to catch anaerobic and aerobic bacteria. Soybean-casein digest medium is kept at 20–25 °C for aerobic bacteria, yeasts and molds. Both are incubated for no less than 14 days and checked for any sign of growth.
Why it takes 14 days
Many of the organisms that matter are slow growers, or have been stressed by drying or preservatives and sit quietly for days before they multiply. Reading the test early makes it less sensitive, not faster, which is why sterility cannot be expedited and why an order containing it is released when the incubation completes. Why a sterility test takes 14 days explains it in more detail.
What the certificate reports
- Growth or no growth in each medium over the incubation
- Method, incubation conditions and the named analyst
- A COA number anyone can check at Verify a COA
How to order
- Create a free account. Individual or business; an individual account needs only an email address.
- Build the order and submit it. One row per sample. Choose a package that includes sterility, or add it to any sample.
- Get your chain-of-custody form and payment link. Both are emailed the moment you submit and saved on the order in your account.
- Post the vials. Write each Sample ID on its vial and on the package, and add your tracking number to the order.
Sample requirements
For lyophilized powder, 2 mg or more per vial is ideal; we can usually work with less and will tell you before we start if the amount is marginal. For reconstituted solution, send at least 0.5 mL. This test needs its own vial, separate from any other tests on the same material. Pro 7X takes two vials of the same sample, because it includes sterility.
Questions
Why does sterility need its own vial?
The sample is inoculated into growth media and cannot be used for anything else afterwards. Send one extra vial for each sample that includes sterility. Pro 7X includes it, which is why Pro 7X takes two vials.
Can a sterility test be rushed?
No. Expedited turnaround buys a faster instrument slot for chromatography; it cannot shorten an incubation. Rapid microbiological methods exist, but they have to be validated against the compendial test for each specific product before they can replace it.
Does sterile mean free of endotoxin?
No. Endotoxin outlasts the bacteria that shed it. Order the endotoxin test as well if that matters to your work.