Sometimes,
unexplained results occur when using biological indicators with sterilization
or decontamination processes. This could be attributable to a failure of the sterilization
process or, perhaps, due to a mishandling of the biological indicator. Other
reasons can be traced to issues of resistance and variations with the
biological indicator itself (the effect of ‘creeping resistance’ has been
described by some microbiologists to indicate a steady rising of D-values).
Atypical results are seemingly more common with hydrogen peroxide vapor cycles
(commonly used for isolator bio-decontamination) compared with sterilization
cycles based on moist heat. In relation to hydrogen peroxide, another reason
for atypical results is due to the occurrence of a rogue biological indicator,
and it with this that this paper focuses on.
Tim
Sandle has written a new article.
Here
is an extract:
A
rogue biological indicator is a term applied to a biological indicator which
survives a hydrogen peroxide vapor cycle when perhaps it should not, based on
the cycle parameters meeting previously established satisfactory profiles and
in relation the known characteristics of the organism (that is, all cells
should theoretically have been killed). When a positive biological indicator
occurs (as evidenced by turbidity in culture media) it is impossible to
determine whether the biological indicator met the definition of a ‘rogue’
(where a rogue can occur due to the overlaying of bacterial endospores on the
carrier, as well as other reasons, as discussed in the main body of this
paper).
As
a note of caution, there are various reasons for isolator cycle failures
outside of the rogue biological indicator situation and the automatic
assumption should be that the reason for a cycle failure is due to a rogue
event. As the rogue event assumes a ‘false positive’, the logical steps is to
attempt to disprove the ‘false positive’ and to identify an alternative reason
for the failure (that is the assumption that the failure is genuine). If no
other reason can be attributed then, and only then, should the possibility of
the rogue biological indicator be assumed. These issues are explored below.
The
reference is:
Sandle,
T. (2020) Rogue Biological Indicators: Are They A Real Phenomenon?, Journal
of Validation Technology, 26 (1):
Posted by Dr. Tim Sandle, Pharmaceutical Microbiology Resources (http://www.pharmamicroresources.com/)
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