Keeping medical devices safe
requires effective sterilization
procedures. Sterilization of
medical devices and ensuring
that biological products are
not contaminated with harmful
agents requires stringent testing
procedures to isolate and identify
any contaminants if they exist.
The FDA has established some
of the requirements for an acceptable
sterility assurance program.
A sterile material is by definition
free from viable organisms.
There are two commonly used
types of sterility methods:
Direct
inoculation of final product
into two different types of
media followed by incubation
at two different temperatures
for 14 days. Turbidity in the
media would be indicative of
the presence of a contaminant
and that contaminant must be
identified. If the test shows
no turbidity in either medium,
it needs to be confirmed by
bacteriostasis/ fungistasis
testing. A negative control
is also included in the assay
to ensure the validity of the
test.
Membrane filtration of the product
through a pre-rinsed sterile
size exclusion filter capable
of retaining bacteria and fungi
followed by dividing the filter
into two parts and inoculating
each one of them into a different
medium. The inoculated media
is monitored over a 14 day period
for turbidity. If turbidity
develops, the organism must
be isolated and identified.
Test articles that are sterile
must be tested for
bacteriostasis/fungistasis.
A negative control is also included
in the assay to ensure the validity
of the test.
Membrane filtration of the product through a pre-rinsed sterile size exclusion filter capable of retaining bacteria and fungi followed by dividing the filter into two parts and inoculating each one of them into a different medium. The inoculated media is monitored over a 14 day period for turbidity. If turbidity develops, the organism must be isolated and identified. Test articles that are sterile must be tested for bacteriostasis/fungistasis. A negative control is also included in the assay to ensure the validity of the test.
The
United States Pharmacopeia and
21 CFR 610.12 recommend using
two media for both the direct
inoculation and membrane filtration
methods. In both cases, the
test article or membrane is
incubated for 14 days in the
two different test media at
two different temperatures.
In order to prevent the occurrence
of false negative results in Sterility
tests due to the presence of inhibitors
in the test article that would inhibit
microbial growth, it is essential
to perform a periodic Bacteriostasis/Fungistasis
test. The test involves the use of
6 organisms of different classes of
bacterial and mold to ensure that
the presence of the presence of the
test article in the same medium with
the indicator organisms does not prevent
or inhibit growth of those organisms.
Sterility Assurance & Bacteriostasis/Fungistasis
Testing