USP General Chapter 71 (revision 5)

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]

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]