Sterility Testing — How We Confirm Every Lot Is Contamination-Free
Sterility testing is the definitive confirmation that a pharmaceutical product contains no viable microorganisms. For injectable water products like bacteriostatic water, sterility testing is performed per USP <71> on every production lot before release. Here is exactly how it works.
USP 71 Sterility Test Methods
USP <71> defines two sterility test methods: (1) Membrane Filtration — the preferred method for bacteriostatic water. The sample is filtered through a 0.45-micron membrane, which retains any microorganisms. The membrane is then transferred to culture media and incubated. (2) Direct Inoculation — the sample is added directly to culture media and observed for microbial growth. Both methods use Fluid Thioglycollate Medium (for anaerobic bacteria) and Soybean-Casein Digest Medium (for aerobic bacteria and fungi).
Incubation and Interpretation
Sterility test samples are incubated for 14 days at controlled temperatures (30–35°C for thioglycollate medium, 20–25°C for soybean-casein digest). Any visible turbidity or growth during this period constitutes a failure requiring investigation. Passing lots show no evidence of microbial growth.
Why Sterility Testing Alone Is Not Enough
Sterility testing confirms no live bacteria or fungi — but it does not detect endotoxins (bacterial cell wall fragments from dead bacteria) or other pyrogens. This is why sterility testing and LAL endotoxin testing are both required for pharmaceutical-grade injectable products. Our COA documents both results.
Sterility Throughout Shelf Life
Sterility testing validates the product at release. Ongoing stability is maintained by the 0.9% benzyl alcohol preservative in bacteriostatic water — which provides continuing antimicrobial protection throughout the 28-day post-opening use period.
How This Relates to Your Order
When you order from Renew Lab Group, every one of these quality steps has already been completed on your lot before it ships. Your Certificate of Analysis documents the specific results — not generic “complies” statements, but actual measured values from the batch you receive.
Quality You Can Verify. Documentation You Can Trust.
HPLC-tested. Endotoxin-controlled. COA included with every order.
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