About Us » Chlorine dioxide gas - Biological Indicators
Biological Indicators
Log Reduction:
1-log = 90%
2-log = 99%
3-log = 99.9%
4-log = 99.99%
5-log = 99.999%
6-log = 99.9999%
(sterilization level reduction)
Biological Indicators (BIs), most commonly inoculated with 106
bacterial spores and referred to as spore strips, are used to challenge
the efficacy of a decontamination/sterilization cycle as they
are considered among the hardest organisms to kill. Sterilization,
often referred to as the 6-log reduction of organisms occurs when
there is a million-fold reduction in living organisms which is why these
spore strips generally consist of approximately 1 million
bacterial spores.
To challenge the decontamination/sterilization cycle,
BIs are placed in hard to reach areas throughout the space being
decontaminated; rooms, isolators, biological safety cabinets, etc. Once
the decontamination
has been completed, the BIs are dropped into growth media using aseptic
technique. If the biological indicator does not produce growth
within the media tube after the incubation period (typically 36 hours),
the decontamination/sterilization cycle is deemed to be successful.
Chlorine Dioxide Gas Biological Indicators:
ClorDiSys uses NAMSA's
Chlorine Dioxide Gas Biological Indicators (NAMSA Code TCDS-06) to test the efficacy of our
decontamination cycles. The BIs consist of 106 Geobacillus stearothermophilus
spores inoculated on a paper substrate and
wrapped in tyvek. We have found these to be the most reliable and
repeatable BIs available for chlorine dioxide gas.
The tyvek creates a barrier to prevent the spores from escaping, and
prevents other organisms from entering post-decontamination
allowing the BIs to be handled and transported easily. The chlorine
dioxide gas molecule is small enough however, to permeate the tyvek and
kill
the spores inside. NAMSA brand BIs and media can be purchased through
the manufacturer or directly through us.
Biological Indicator Locations:
As BIs should always be used to challenge decontamination/sterilization cycles, they must be placed in challenging areas.
ClorDiSys always uses BIs with a population of 106 spores
(that's 1 million spores!) to test our decontamination cycles, even
for our "challenge" locations. Below are some of the more challenging
locations where BIs have been placed during chlorine
dioxide gas decontaminations. All of these challenge location BIs
exhibited 6-log sterilization level kill using our standard cycle.
In Packed Storage Rooms
(BI was placed at the bottom of the closest trash can) |
Inside Packed Isolators
(Over 30 BIs were placed inside) |
Inside Water Bottles
(BI at bottom of middle bottle of middle rack) |
Inside Closed Trash Can
|
Inside Closed Cabinets
(cabinet on right is closed) |
Inside Closed Drawer
(Drawer on right is closed) |
Underneath Dust
(such as in HEPA filters) |
In HEPA Filter
(BI between pleats of HEPA Filter) |
Underneath Printers and Other Equipment
|
In Stacks of Filtered Cage Lids
|