USP General Chapter 71 (revision 9)
Old revision·09:47, 6 Feb 2025·GlossaryGleb
| USP General Chapter 71 | |
|---|---|
| Title | Sterility Tests |
| Status | Mandatory where referenced |
| Methods | Membrane filtration; direct inoculation |
| Topic infobox · conventions | |
USP General Chapter 71, titled Sterility Tests, prescribes the media, incubation conditions, sample quantities and method-suitability procedures for demonstrating that a sample yields no microbial growth. It is a mandatory chapter where a monograph or regulatory requirement invokes it.[1]
The chapter is explicit that a passing result is not proof of sterility of a batch. Sterility assurance derives from process design and validation; the compendial test is a final check with limited statistical power, and the chapter's companion informational chapter on sterility assurance says so at length.[2]
Like the endotoxin chapter, it is harmonised in substance with the corresponding European and Japanese pharmacopoeial chapters.[1]
What the chapter specifies
[edit]The chapter names two media — fluid thioglycollate medium, incubated at 30–35 °C, and soybean–casein digest medium at 20–25 °C — and requires incubation for not less than fourteen days. It specifies growth-promotion testing of each medium lot against named challenge organisms before use.[1]
Sample quantities are tabulated by container size and batch size. The number of containers tested is small in absolute terms, which is the source of the statistical limitation discussed at Sterility testing.
Method suitability, formerly called the bacteriostasis and fungistasis test, requires demonstrating that the sample does not inhibit growth of the challenge organisms under the conditions used. Where the sample is inhibitory, the method must be modified — by filtration and washing, by neutralisation, or by dilution — until recovery is demonstrated.[1]
Membrane filtration and its limits
[edit]Membrane filtration is preferred where applicable because it separates the sample from the growth medium: the organisms are retained on a 0.45 μm membrane, the sample and any inhibitory component pass through, and the washed membrane is incubated.[1]
The pore size is a compendial convention rather than an absolute cut-off. Organisms smaller than the nominal rating exist, and filtration is a retention process rather than a sieve, so retention is probabilistic. This is one of several reasons the chapter is framed as a test rather than as proof.