In the Resistance Performance Tests section of USP 31, it states to culture biological indicators (BI) ‘within a noted time, not more than four hours’ after the sterilization process. In reality however, this is not always possible due to several different situations. For instance, many ethylene oxide cycles can take several hours to aerate post-sterilization preventing access to the load and the BIs contained within. Clinical monitoring services will also have difficulty meeting this 4-hour window due to the fact that these services are mailed exposed indicators from a clinical setting for culturing and the BI may be in transit for a number of days before they are able to be transferred into culture media and incubated.
In the July 2013 Spore News[DD1] , Eric Gillitzer, PhD., takes an in-depth look at what effect extended periods of time between exposure and BI transfer has on the results of an exposed biological indicator. Two complete studies were performed that compare BIs transferred immediately after exposure and then also after extended periods to gauge whether or not there is an impact on the D-value of the indicators and to determine if the injured spores remain viable if they are not transferred within this 4-hour window. Click here to read the full Spore News article.
Spore News is produced bimonthly and is written by a rotating series of authors from Mesa’s Biological Indicator division looking at common issues within the biological indicator community. Click here to sign up to receive Spore News and to review past issues looking at dozens of sterilization monitoring situations and studies.
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