It is essential that all microbiological tests
are quality controlled to guarantee the result is true and this will normally
form part of a laboratory's accreditation compliance. Part of the QC procedure
requires that standard or type culture organisms are used to represent 'real
samples' but in a controlled manner. These should be traceable back to a known
type culture with normally less than five subcultures or passes (repeated
subculture of organisms can result in possible genetics changes or
contamination). Many organisms for QC are available commercially in a range of
different presentations, these are easy to store, easy to use (with little or
no preparation time), economical and most importantly reliable and consistent.
There are a range of applications for which these quality control organisms can
- Media QC
media prepared in house will require various growth promotion tests according
to GLP, even with commercial ready to use media where most of the QC testing
work has already been done, some limited growth promotion testing is still
needed, particularly with media containing light or heat sensitive components.
- Positive and Negative Controls for biochemical tests, kits and slide
using qualitative inoculant for assays, kits and slide staining, the controls
should reflect the organism(s) being tested for and demonstrates that the test
was correctly performed. Slides for Gram and Acid Fast staining are available
with positve and negative control organisms already incorporated.
- Antimicrobial Efficacy Testing or MIC Determination
reference strains of bacteria with known sensitivites are tested in
parallel with the clinical culture to to monitor antimicrobial content of the
discs/broths and the performance of the media and incubation conditions.
- Determining Measurement of Uncertainty (MOU)
as no method is perfect, by using a quantitative inoculum the amount of
uncertainty for a particular assay can be calculated, commercial products are
an easy standardised way of using a known inoculum number.
- Determining Limits of Detection
of qualitative or quantitative routine testing or for method validation,
particularly useful if naturally contaminated materials rarely occur.
- Challenge testing /Preservative Efficacy Testing (PET)
using quantitative preparations of known organisms a products preservative
system can be challenged and monitored using a reliable and consistent
Packaged QC organisms are also very useful during method
validation, particularly for determining measurement of uncertainty (MOU),
limits of detection and other tests where a quantitative inoculant is required.
When using the quantitative systems they provide greater precision and
consistency batch-to-batch than self prepared organisms.
The format the QC organisms are supplied in varies, from a film of preserved
organisms in the lid of a vial to freeze-dried discs or beads. All are
rehydrated in some form prior to use. Some need to be kept refrigerated, others
require freezing. The systems supplied in vials can be used with a pipette or
culture loop, others are presented in a swab format that can be streaked
directly onto a plate.
ATCC Licensed Derivative Program
ATCC runs a license program to ensure the integrity of culture organisms purchased in commercial formats. By joining the ATCC Licensed Derivative Program, companies agree to maintain the integrity of the ATCC ingredient and allow ATCC to verify the quality of the ingredient before it reaches end-users. In return, the ATCC Licensed Derivative emblem assures customers of the quality of the ATCC ingredient contained in the product. For more information about the ATCC Licensed Derivative Program and the companies that are currently licensed under this program, please click here