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Microbiological evaluation of sterile barrier systems

General remarks.  The aim of this website is to promote data-based control procedures to maintain sterility of terminally sterilized products at the sterility assurance level (SAL). Health care personnel must have experience and understanding of how packaging systems of terminally sterilized medical devices, i. e. sterile barrier systems, should be selected and used in order to maintain product’s sterility and to reduce the risk of hospital acquired infections (HAI). According to the International Standards ISO 11601-1 and 11607-2 conditions such as temperature, humidity, atmospheric air pressure and bioburden under which the packaging system is exposed during storage and/or transport should be recorded and controlled. The sterile barrier system must correspondingly reflect theses conditions by having specific material performance properties. Medical packaging, packaging processes, transport and storage must be validated in respect of different International Standards in their current editions such as ISO 11607-1, ISO 11607-2, EN 868, Part 2-10, ISO 17664 and others. Guidelines and manufacturers’ instructions for use have to be considered.
This website gives examples and methods which should contribute to ensure to maintain product’s sterility. Certain limitations of the presented method have to be pointed out. For example, specific physical factors such as temperature changes or face velocity that influence the air flow into porous packaging material, are not considered in the presented data-based shelf life calculation model. These effects should not be neglected. Furthermore, gaps in the knowledge base with respect to the diffusion of airborne micro-organisms through the porous packaging material should be mentioned in this context.

Introduction
Medical packaging material for non-liquid sterile products in hospitals  such as sterilization containers, paper/film constructions and paper or nonwoven sheets is normally porous or has porous components to ensure sterilant access. The probability of entering of airborne micro-organisms depends on the air volume that passes through the porous packaging material, the airborne microbial concentration and the filtration efficiency of the porous components.The sterile barrier system has to meet certain requirements:
  • Sufficient permeability to remove the air inside the packaging and to allow gaseous sterilants such as steam or ethylene oxide to enter the packaging.
  • Sufficient microbial barrier efficiency to maintain sterility and to protect the medical device against recontamination by means of handling and environmental contact.
  • Sufficient microbial barrier property against airborne micro-organisms by means of filtration efficiency (ISO 11607-1).

Air flow into the packaging is dependent on environmental factors. It is caused by temperature and weather dependent air pressure changes or transportations to different altitudes. Therefore, a data based assessment of the compatibility of sterile barrier system with the environmental airborne microbial challenge is necessary.