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Sterility Testing
Sterility is defined as the absence of viable microorganisms. Here at Eagle
Analytical Services, we utilize only the USP methods for analyzing compounded
pharmaceuticals. The membrane filtration method is used when the nature of the
product permits. If the membrane filtration technique is unsuitable, direct
inoculation of the culture medium must be utilized.
When choosing Eagle Analytical Services, you have two choices when it comes to
the type of membrane filtration test performed on your compound. The first is
the traditional membrane filtration method, as stated in USP<71>. The
second method utilizes the Millipore Steritest™ System, also a USP <71>
method and considered the gold standard in the major pharmaceutical industry.
The difference in the two techniques is that the Steritest™ method is a
completely closed system in which there is very little chance of obtaining a
false positive result. Regardless of the above method chosen for your sterility
test, the basic methodology is the same, to meet the requirements of the USP.
Eagle Analytical Services only permits degreed personnel properly trained in
microbiology to perform sterility testing in our certified Class 100 biological
safety cabinet, located in our certified Class 100 clean room. Sterility
testing is a very exacting procedure, where asepsis of the procedure must be
ensured for a correct interpretation of the results. Link to submission form.
Membrane Filtration Sterility Testing
According to USP <71> Sterility Tests membrane filters with a nominal
pore size of not greater than 0.45µm must be used. The minimum requirements for
a sample to be analyzed can be found in USP<71>. The sample is filtered
and rinsed with the appropriate sterile diluent. The membrane is aseptically
cut into two equal parts and transferred into each of the two suitable media.
The media is then incubated for not less than fourteen (14) days.
The media found to be suitable for sterility testing are Fluid Thioglycollate
Medium and Soybean-Casein Digest Medium. The fluid thioglycollate medium is
primarily intended for the culture of anaerobic bacteria, as well as aerobic
bacteria. The soybean-casein digest medium is suitable for the culture of both
fungi and aerobic bacteria. Once inoculated, the fluid thioglycollate medium is
to be incubated at 32.5°c ± 2.5° and the soybean-casein digest medium is to be
incubated at 22.5°c ± 2.5°.
Eagle Analytical Services examines the media on the third and seventh day after
the test has begun, as well as at the conclusion of the fourteen (14) day test,
for any evidence of microbial growth. At the conclusion of the fourteen (14)
days, if the sample being tested renders the medium turbid so that the presence
of microbial growth cannot be determined, USP <71> specifies that a
portion of the medium be transferred to a fresh vessel of the same medium. The
original and transfer vessels are then incubated for an additional four (4)
days for analysis. Link to submission form.
Millipore Steritest™ Sterility Testing
The unique design of the Millipore Steritest™ incorporates the sampling,
filtration, rinsing, media addition, and incubation into a completely enclosed
system. This allows the sample, sterile diluent, and media to remain in a
completely sterile setting, never being allowed access to the environment. This
reduces the risk of false positive results. The Millipore Steritest™ System is
considered the gold standard in the pharmaceutical industry. Major
pharmaceutical companies utilize the Steritest™ for their sterility testing.
As indicated in USP <71> membrane filtration is the preferred method of
sterility testing, as long as the sample is filterable, as opposed to direct
inoculation. The Millipore Steritest™ utilizes the membrane filtration method.
A peristaltic pump directly transfers the sample, through enclosed tubing,
equally dividing it into two sealed canisters. Membranes are located at the
bottom of the sealed canisters. The liquid is filtered out allowing any
contaminants to remain on top of the membrane, inside the sealed Steritest™
canister.
After filtration and rinsing, the two types of media are introduced to the
canisters through the same tubing. No membrane transfer is required. The
canisters, with the appropriate medium, are then incubated at the temperatures
required in USP <71> for not less than fourteen (14) days.
The media found to be suitable for sterility testing are Fluid Thioglycollate
Medium and Soybean-Casein Digest Medium. The fluid thioglycollate medium is
primarily intended for the culture of anaerobic bacteria, as well as aerobic
bacteria. The soybean-casein digest medium is suitable for the culture of both
fungi and aerobic bacteria. Once inoculated, the fluid thioglycollate medium is
to be incubated at 32.5°c ± 2.5° and the soybean-casein digest medium is to be
incubated at 22.5°c ± 2.5°.
 Eagle
Analytical Services examines the media on the third and seventh day after the
test has begun, as well as at the conclusion of the fourteen (14) day test, for
any evidence of microbial growth. At the conclusion of the fourteen (14) days,
if the sample being tested renders the medium turbid so that the presence of
microbial growth cannot be determined, USP <71> specifies that a portion
of the medium be transferred to a fresh vessel of the same medium. The original
and transfer vessels are then incubated for an additional four (4) days for
analysis.
Click here to
download Sample Submission form.
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