| Calculation of Surviving Spores on Biological Indicators Used to Monitor Gaseous Sterilisation Heribert Häusler and Michael Pfeiffer Pharma Manufacturing Division, Quality Operations Department, Boehringer Ingelheim Pharma GmbH & Co. KG, Ingelheim/Rhein (Germany) Correspondence: Dr. Michael Pfeiffer, GFB Pharma-Herstellung, Abteilung Quality Operations, Boehringer Ingelheim Pharma GmbH & Co. KG, 55216 Ingelheim/Rhein (Germany), e-mail: Michael.Pfeiffer@ing.boehringer-ingelheim.com
The use of biological indicators (BI) to monitor the effectiveness of sterilisation is described, amongst other places, in the European Pharmacopoeia. (Reference) sterilisation parameters are also specified for three methods: for sterilisation using moist and dry heat and for sterilisation by irradiation. These parameters ensure adequate and safe sterilisation, with observance of a sterility assurance level (SAL) of 10-6and below. This means that routine use of biological indicators to monitor the effectiveness of sterilisation is not necessary in these cases. Routine use of biological indicators is only mandatory in the case of gaseous sterilisation.
Knowledge of the D-value of the biological indicator is useful for determining the adequate gas exposure time. However, the certified D-value is only valid under defined sterilisation conditions which are often different from those in routine sterilisation. In the latter case, the D-value must be redetermined under routine sterilisation conditions. The European standard, EN 866, specifies how the D-value(s) is / are to be determined in such cases. These normative requirements are difficult to implement in practice. In such cases, a “combination” of practical considerations and normative requirements should be used to identify solutions in individual cases.
Key words Biological indicators, international standardisation, most probable number of survivors • D-value • Gaseous sterilisation |
