All Device Manufacturers/Repackers Using Cotton

Since August 1993, the Center for Devices and Radiological
Health  (CDRH) has become aware of several instances where
devices made of Chinese cotton have been found t o  be
contaminated with mold, even though the devices were labeled
as sterile.  Devices containing cotton include, but are not
limited t o  laparotomy sponges, surgical sponges, surgical
drapes, operating room towels and wound dressings.  T o  date,
w e  have not noted problems regarding cotton grown in other
countries, including the United States.  As a precaution, the
following information sheuld be considered regardless of the
c o t t o n l s  origin.
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The prevalent mold which has been identified thus far is
Pvronemia domesticum, which belongs to the class Ascomycetes
and is believed to be nonpathogenic.

Several companies who have experienced problems with mold
have changed their sterilization practices.  One manufacturer
has determined that P.  domesticum is resistant to standard
ethylene oxide  (EO) sterilization cycles and to standard
gamma radiation doses.  The manufacturer is using a standard
steam sterilization cycle followed by  a standard EO
sterilization cycle.  Other companies have instituted a
standard EO sterilization cycle followed by  a standard gamma
radiation cycle, or vice versa.

CDRH is not advocating any of the above methods, but is
recommending that you conduct appropriate, adequate and
thorough validation studies of each sterilization cycle in
use.  The sterilization validation studies should not only
focus on bacterial contamination, but  should also include
molds and yeasts.  The following points should be  included a s
part of your sterilization validation:

1.  Bioburden of the incoming cotton device.  The bioburden
assessment must include bacteria, molds and yeasts using
established test methods.  The entire device must be
submerged in the culture media.  Bioburden should be assessed
as part of sterilization cycle development, and then periodic
bioburden assessment should be performed once the cycle h a s
been validated.

2 .   Sterilization cycle development studies should include
inoculated product using P. domesticum and any other
microorganisms found during initial bioburden assessment.
The inoculated product should be placed in the hardest to
sterilize locations within the chamber.  Standard methods should be utilized for inoculation, recovery and culture techniques.  Again, the entire device must be submerged in
the culture media.  If gamma radiation is used to sterilize
the device, our experience has shown that incubation up to 3 0
days may reveal slow growing microorganisms which were not
found at the traditional 14 day incubation period.

Use of  inoculated product should not preclude the use of
biological indicators and/or dosimeters during validation and
during routing processing.

3.  During validation, sterility testing of the sterilized
cotton should be performed using established test methods.
The testing regimen should include identification of
bacteria, molds and yeasts.  Again, the entire device must be
submerged in the culture media.  Traditionally, FDA does not
require that routine sterility testing be conducted on each
sterilization load, provided that the sterilization process
has been properly validated.  However, for cotton deyices, it
is recommended that at least periodic sterility testing be
performed t o  assess that the cycle is adequate.


All Device Manufacturers/Repackers Using Cotton (PDF Version) (PDF - 105KB)
If you have any questions regarding this letter, you may
contact John Samalik of the General Surgery Branch at the
above address or at  (301) 594-4595.