Laboratory Series#19: Viral Transport medium
In the current scenario of coping with large diagnostic load, a lot of people have asked me on use of VTM in Viral diagnostics. Here are the absolute basics. Viral transport medium is a liquid media that can sustain the virus numbers, infectivity and reduce or inhibit any possible contaminants (such as bacteria or fungus). As already noted, VTM is not a universal requirement. In some cases, the sample may be submitted for analysis as it is. Samples including CSF, blood, BAL and urine samples can be simply sent in a cold chain. For other samples such as tissue biopsies, nasal swabs, skin swabs etc. VTM is preferred. There a large number of commercial and inhouse formulations of VTM available. Each of these supports good recovery of a few range of viruses. The basic components of all these viral transport media is a buffer solution with protective components such as proteins or charcoal and a PH indicator. A widely accepted principle is that VTMs are isotonic in nature. However, this is
