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Guidelines for sterility testing of therapeutic goods

13 September 2006

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Annex IV. Sterility test environment

This Annex provides guidance for achieving a testing environment that is equivalent to the conditions required for the aseptic manufacture of pharmaceutical products, as required by the BP/Ph Eur (section 'Precautions against microbial contamination'). It incorporates relevant elements from the Pharmaceutical Inspection Convention/ Pharmaceutical Inspection Co- operation Scheme (PIC/S) Recommendations on Sterility Testing (April 2000), Annex 1 of the PIC/S Guide to Good Manufacturing Practice for Medicinal Products (August 2001) and the Australian Code of Good Manufacturing Practice for Medicinal Products Annex 1 – Manufacture of Sterile Medicinal Products.



Sterility testing should be performed under conditions that meet Class 3.5 of Australian Standard 1386 or the equivalent European Class A (see Table 6).

The BP/Ph Eur requires that sterility testing is carried out 'under aseptic conditions'. Guidance is provided that these conditions can be achieved using, for example, a class A laminar-air-flow cabinet located within a class B clean-room or an isolator' (BP/Ph Eur: 'Precautions Against Microbial Contamination').

A Class 3.5 laminar flow cabinet stationed within an AS Class 350 clean-room meets these criteria. There is no direct equivalent in AS 1386 to a class B environment, however, the counts accepted for an AS class 350 room are the same as for a class B room 'in-operation'. Acceptable alternatives are a Class 3.5 / Class A clean-room or an isolator.

For the testing of potentially dangerous drugs an appropriate laminar flow cabinet with a protective air curtain or an isolator should be used.

Table 6: Clean-room environment classifications
Environment European (PIC/S) Australian (AS 1386)


number of particles
≥0.5 µm / m3


Number of particles
≥ 0.5 µm / litre

at rest

in operation

in operation

Laminar flow cabinet; Isolator


3,500 3,500





3,500 350,000

not defined


350,000 3,500,000 350



3,500,000 not defined 3,500


The testing work zone should provide sufficient space and material should be set out so as not to disrupt laminar air flow.

Air supply

Air supplied to the environment should be provided through terminal HEPA filters that should be fitted with audible and/or visual alarms to indicate pressure drop across the HEPA filters. There should be a pressure differential of 10 to 15 Pascals (guidance value) between each of the areas, ie, ambient/airlock and airlock/test room. A minimum of 20 air changes per hour is expected. Prior to operator entry to the test suite, pressure readings should be taken and recorded from externally mounted gauges labelled to indicate the area served, acceptable specification and whether or not the reading is absolute or differential. An automated continuous monitoring system is an acceptable alternative to manual reading.


The test environment, which includes the laminar flow cabinet or isolator, should be certified at least annually by a competent person for compliance with the specified conditions.


Entry to the clean-room should be via an airlock where operators change into clean-room garments. The airlock should be designed to facilitate movement of the operator from the unclean to the clean end of the room without compromising the aseptic gowning procedure. A step-over bench is a suitable division between these areas. The airlock should contain a full- length wall mirror, gowning instructions and hand washing/drying facilities.

Clean-room fittings and surfaces

The clean-room should have a minimum of ledges and obstructions to flow of clean air. In general, fittings such as power outlets and light fittings should be flush with  walls/ceiling surfaces and sealed to prevent the entrainment of unclean air. Surfaces should be smooth and impervious to the cleaning agents used. The joints between walls/ceilings/floors should be coved to facilitate cleaning. The intercom or communication system should be designed to allow hands-free use. Chairs, trolleys and such items should be designed to facilitate cleaning and be suitable for clean-room use.

There should be no extraneous equipment within the clean-room environment.

Ultraviolet lights may be fitted only in pass-through hatches. If there is more than one parallel tube they should be shielded from each other. They should be checked at least annually or whenever new lamps are fitted.

Cleaning, sanitisation and disinfection

There should be written instructions for daily, weekly and periodic cleaning and decontamination of the test suite. If an isolator is used, the method of disinfection/sterilisation should be specified. Disinfectants should be free of microbiological contamination, which may be achieved by aseptic filtration or use of a product-compatible terminal sterilisation method. All disinfectants and detergents should be monitored by testing for contamination.

All cleaning, sanitising and disinfecting procedures should have been validated for minimum contact time and efficacy.

Surfaces and operators' gloved hands should be disinfected regularly during the test session.

Environmental monitoring

Environmental monitoring should consist of air sampling, settle plates, surface monitoring and operators' gloved hand plates. Surfaces can be monitored by contact (RODAC) plates, films or swabs. The laminar flow area should be monitored as well as the background room area.

Written procedures should specify exposure duration, frequency and location of all monitoring and include appropriate alert and action limits for microbial contamination. The media used should be specified and the recovery of micro-organisms from surfaces and on media should be validated. Suitable disinfectant/cleaning agent inactivators may need  to  be incorporated in media.

Records should be maintained of the numbers and types of organisms isolated and results presented in a format that facilitates early detection of trends. Routine identification of environmental micro-organisms to at least the genus level should assist in detecting trends. If the identity of organisms from the environment is to be used as the basis for invalidating a sterility test and performing a repeat sterility test, then a sensitive method of identification such as molecular typing techniques using RNA/DNA homology will be expected.

Testing Ancillary to the Sterility Test

The exposure and manipulation of cultures increases the likelihood of environmental contamination. Testing associated with the sterility test but requiring the use of live micro- organisms (eg validation, stasis testing) should be carried out in laboratory facilities that are completely separate from the clean-room. In addition, such aspects of testing for sterility that necessitate the handling of live cultures should not be carried out in or adjacent to production areas.

Sterility Testing Operators


Sterility testing should only be performed by personnel who have been trained, qualified and certified to perform the various tasks and procedures related to sterility testing. The examination of test and control containers during and at the end of the incubation period should be included as part of the operator training program. Personnel should undergo periodic re-certification, particularly when problems are detected during the course of routine environmental and negative control monitoring, or when operators perform the test infrequently.

The operator's testing technique should be monitored during every test session by use of negative product controls. Techniques used should be reviewed periodically to ensure that departures from aseptic practices do not develop. Personnel training should be documented and records maintained.

Clean-room garments

The sterility test operator should wear sterile clean-room garments that consist of a one-piece coverall suit, a head cover, a beard cover if applicable, overshoes, gloves and mask. The use of sanitised garments may be acceptable if the process has been validated and their use is not used to justify the performance of repeat sterility tests. These garments should be changed for each work session, or at least once daily if validated by personnel monitoring.

Each operator should be trained and certified in aseptic gowning procedures as part of training for sterility testing, and training records maintained. Records of sterilisation of garments should be kept. This may be in the form of a certification from an external supplier of clean-room garments.

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