Viral Transport Media, or VTM, is a liquid solution used to collect, transport, and maintain clinical specimens suspected to contain viruses, chlamydia, ureaplasma, or mycoplasma organisms. It comes in single use tubes, bulk containers, or even specimen collection kits. Once samples are collected via a sampling tool, such as a sterile swab, the collection tool is carefully transferred into the VTM and sealed for transport to the laboratory. The solution acts to maintain organism viability until testing can be completed.
There are several classifications of transport mediums, but VTM is typically a non-propagating culture media, which means if viruses are present they remain viable, but do not reproduce. This type of VTM usually contains buffers and proteins to mimic physiological conditions found within our bodies. This is done to prevent attenuation of the virus prior to testing; however, most NAAT (nucleic acid amplification tests) used today do not require viability, they only need the virus to be present for detection. Antibiotics are also incorporated into the media to inhibit or suppress background flora that is present in samples. If you think about where a swab goes for sampling, it is not surprising to know that bacteria and fungi are also present. If cultures of these organisms are also required, separate specimens must be collected and and different transport media, such as Amies Medium, should be used.