Poor hygiene is not only found in clinical practice but also in the manufacture and distribution of medical materials (1). The most frequently occurring errors include failure to observe well-known rules of hygiene, e.g., removal of jewellery from hands and arms before starting work or full covering of the hair on the head and face throughout the operation (category IB of the Robert Koch Institute guidelines).
For sterile medical devices the norm is the sterility assurance level of 10–6, i.e., the probability of non-sterility should be equal to or less than 1:1 000 000. To monitor the maintenance of sterility during storage, information is needed on the filtration capacity of the air permeable components of the packaging material, in order to estimate the risk of recontamination by airborne microorganisms (see ISO 11607–1) (2, 3). Unfortunately, this information is currently rarely supplied by the manufacturer. The airborne microbial challenge (N0) of terminally sterilized products is dependent on the airborne microbial concentration (particle size ≤ 3 µm) and the volume of air that enters the packaging during storage, which depends in turn on fluctuations in air pressure and temperature (see the Boyle-Mariotte and Gay-Lussac laws). According to the calculation N0× (100 – filtration capacity in %): 100 × n ≤ 10–6, commercial paper-based packaging material, with a relatively high filtration capacity of 99 %, guarantees sterility for only a few days at the required level, even in optimal storage conditions (20 colony-forming units per m3 of air, changes in temperature and air pressure not exceeding 2 °C and 15 hPa, packaging volume 100 cm³, n = frequency of changes in temperature and air pressure).
Millions or even billions of terminally sterilized products are used every day around the world. Therefore, even a low rate of non-sterility increases the risk of nosocomial infections that could be avoided by paying greater attention to the filtration capacity of the packaging material in relation to storage conditions. Not every requirement—as Tacconelli et al. (4) themselves write—has to be based on evidence.
Footnotes
Conflict of interest statement
Prof. Dunkelberg has received payments from Kimberly-Clark. He holds a patent related to the topic of the article discussed.
References
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