OXA-48 - FAQ
What are the variants that are recognized by our RESIST tests?
What are the bacterial species tested for the different carbapenemases of our tests?
What are the culture media compatible with the kit?
Is the buffer the same for all Coris BioConcept's K-SeT kits? If I need some more for my tests, may I use the one from another kit?
According to the "Instructions For Use", it is not allowed to exchange buffer between kits. If you have volume problems, please contact your distributor who is able to provide additional vials. Nevertheless, the buffer is the same within one product of different lot numbers (e.g. Rota-Strip buffers exchange between different lots will not give rise to any problems on the strips).
At present, 8 different kinds of buffers are used in Coris’products, i.e., RE-A Buffer (for Influ –A&B Respi K-SeT), Extraction Buffer (for RSV-Strip), HC Dilution buffer (for Adeno Respi-Strip, Combi-Strip, Pylori-Strip, GastroVir-Strip, for Crypto-Giardia Duo-Strip, Giardia-Strip, and all cassette formats of the corresponding kits), HydroK buffer (for dry swab Test restricted to AdenoRespi K-SeT), ST-A buffer (for C.diff-Strip and Clostridium K-SeT), LY-A Buffer (for RSV Respi K-SeT and for kits RESIST), BL-A Buffer (for HAT Sero K-SeT), ST-1/ST-2 Buffers (for Strep-A Respi-Strip), and Sample Dilution Buffer for all the other products.
Regarding the GastroVir Kit we received some particular comments claiming that the Control Line was too faint. The buffer has been improved to allow a better migration of the latex microspheres leading to a better and a more homogeneous signal. This improvement does not affect any characteristics of the kit (i.e. specificity and sensitivity).
What happens when a clinical specimen is a strongly positive specimen? What about the control line?
There are two different kinds of conjugates – a specific reagent for test line and a specific reagent for the control line - in the strip. A strong positive specimen has NO effect on the intensity of the control line onto the nitrocellulose of the strip. As long as the control line appears - with whatever intensity level - the test should be regarded as valid.
Why does the control line sometimes appear very weak while the test line is positive?
Control line is aimed to ensure that chromatography has been performed up to the top of the strip. It is not related with the result of the diagnostic itself.
Sometimes, the control line might be "slightly weak "without any precise reason. It could be only an effect of the sample migration and / or responsiveness at the control line. The control line is aimed to validate the test using various specimen.
How to use correctly K-SeT kits from Coris BioConcept?
Always store the reagents at the indicated storage temperature : between 4 and 30°C for all kits
Aways use gloves to manipulate kit components and samples
Always use the provided (Extraction, Dilution, …) Buffer even if the sample is already diluted (e.g. in a transport medium)
Always be sure that the solution sample – buffer is homogenous before testing
Always read the results when the dipstick into the device is wet (between 10 and 15 minutes depending on the test
How long can a pouch remain open before performing the test?
Once the pouch is opened, the test should be performed immediately. An unopened pouch may be kept at between 4 and 30°C and used until the shelf-life date indicated on the packaging.
The liquid does not migrate in the cassette, what should I do?
The most plausible hypothesis to explain the invalid test (no control line after running) is a problem of sample volume poured into the sample well of cassette.
In the notice, the instructions for use stipulates to dispense 3 drops of diluted sample delivered by the collection tube with dropper provided with the kit. However, if you put only 2 drops of diluted samples in tube, the conjugate may not be released completely from the pad where it is dried, and the reduced liquid volume does not allow a correct and complete migration on the strip in the cassette. We recommend to perform a new cassette test with 3 drops of preparation of diluted sample to recover the correct migration. Contact Coris (cc) if you encounter again this technical problem.
Is it a problem if the test has "run" more than the recommended time?
Yes. It might cause the appearance of false positive signal on test.
The signal of the test line is very weak in comparison with the control line. Do I have to consider that the result is positive?
The control line is aimed to ensure the user that the chromatography is performed up to the top of the strip. It does not give any indication on the diagnostic result. Whenever a signal is observed on the test line (weak or strong), it means that the result of the test is positive for the pathogen of interest.
What type(s) of sample(s) are compatible with the test OXA-48 K-SeT test?
To date, the OXA-48 K-SeT kit has allowed to detect OXA-48 carbapenemase from 10 bacterial species (Citrobacter braakii, Citrobacter freundii, Enterobacter aerogenes, Enterobacter asburiae, Enterobacter cloacae, Enterobacter kobei, Escherichia coli, Klebsiella oxytoca, Klebsiella pneumoniae, Serratia marcescens). Moreover, 7 OXA-48 family variants have been detected (OXA-181, OXA-162, OXA-204, OXA-232, OXA-370 from K. pneumoniae, and OXA-204 and OXA-244 from E. coli.
What are the OXA-48 clinical strains detected by the test OXA-48 K-SeT?
The OXA-48 K-SeT test is designed to be used with a bacterial colony on solid medium. Other sample types are currently investigated.