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Peracetic acid is a highly biocidal oxidizer that maintains its efficacy
in the presence of organic soil. Peracetic acid removes surface
contaminants (primarily protein) on endoscopic tubing. An automated
machine using peracetic acid to sterilize medical, surgical, and
dental instruments chemically (e.g., endoscopes, arthroscopes) was
introduced in 1988. This microprocessor-controlled, low-temperature
sterilization method is commonly used in the United States. The
sterilant, 35% peracetic acid, and an anticorrosive agent are
supplied in a single-dose container. The container is punctured at
the time of use, immediately prior to closing the lid and initiating
the cycle. The concentrated peracetic acid is diluted to 0.2% with
filtered water (0.2 μm) at a temperature of approximately 50°C. The
diluted peracetic acid is circulated within the chamber of the
machine and pumped through the channels of the endoscope for 12
minutes, decontaminating exterior surfaces, lumens, and
accessories.
Interchangeable trays are available to permit the processing of up to
three rigid endoscopes or one flexible endoscope. Connectors are
available for most types of flexible endoscopes for the irrigation
of all channels by directed flow. Rigid endoscopes are placed
within a lidded container, and the sterilant fills the lumens either
by immersion in the circulating sterilant or by use of channel
connectors to direct flow into the lumen(s). The peracetic acid is
discarded via the sewer and the instrument rinsed four times with
filtered water. Concern has been raised that filtered water may be
inadequate to maintain sterility. Limited data have shown that
low-level bacterial contamination may follow the use of filtered
water in an AER but no data has been published on AERs using the
peracetic acid system. Clean filtered air is passed through the
chamber of the machine and endoscope channels to remove excess
water. As with any sterilization process, the system can only
sterilize surfaces that can be contacted by the sterilant.
The manufacturers suggest the use of biological monitors (Geobacillus
stearothermophilus spore strips) both at the time of
installation and routinely to ensure effectiveness of the process.
The manufacturer’s clip must be used to hold the strip in the
designated spot in the machine as a broader clamp will not allow the
sterilant to reach the spores trapped under it. One investigator
reported a 3% failure rate when the appropriate clips were used to
hold the spore strip within the machine. The use of biological
monitors designed to monitor either steam sterilization or ETO for a
liquid chemical sterilizer has been questioned for several reasons
including spore wash-off from the filter paper strips which may
cause less valid monitoring. The processor is equipped with a
conductivity probe that will automatically abort the cycle if the
buffer system is not detected in a fresh container of the peracetic
acid solution. A chemical monitoring strip that detects that the
active ingredient is >1500 ppm is available for routine use as an
additional process control.
Microbicidal Activity.
Peracetic acid will inactivate gram-positive
and gram-negative bacteria, fungi, and yeasts in <5 minutes at <100
ppm. In the presence of organic matter, 200-500 ppm is required.
For viruses, the dosage range is wide (12-2250 ppm), with poliovirus
inactivated in yeast extract in 15 minutes with 1500 to 2250 ppm.
Bacterial spores in suspension are inactivated in 15 seconds to 30
minutes with 500 to 10,000 ppm (0.05 to 1%).
Uses.
This
automated machine is used to chemically sterilize medical (e.g., GI
endoscopes) and surgical (e.g., flexible endoscopes) instruments in
the United States. Lumened endoscopes must be connected to an
appropriate channel connector to ensure that the sterilant has
direct contact with the contaminated lumen.
See the complete recommendations on sterilizer and disinfection at
www.cdc.gov
“Guideline for Disinfection and Sterilization in Healthcare
Facilities, 2008”. ATS, Inc. also stocks a monitoring system using
Geobacillus stearothermophilus spores to test the Peracetic Acid
Sterilization equipment – see
Supplies.
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