Introduction of Viral Transport Medium (VTM)
Viral transport medium brief form is VTM and it uses to transport viruses to maintain viability.
Storage and Transportation
The Sooner the specimens reach the laboratory the better.
1. By lowering the temperature
Short term storage: +4°C and long term storage: -70°C/-190°C(liquid nitrogen)
2. Virus Transport Medium: Specimens are emulsified in the medium.
Composition of Viral Transport Medium
Following are the ingredients of VTM-
- buffered salt solution
- Proteins (Bovine serum albumin)
- Antimicrobial agents
- Indicator
Method of using VTM
- First of all, open the sealed pouch.
- You will get a swab stick and VTM.
- Take the specimen with a swab stick and emulsify it in the medium.
- Break the swab stick from the breaking point and recap the VTM.
The function of Viral Transport Medium:
- Preserves viral infectivity within the specimen
- Prevents specimen from drying
- Prevents growth of bacteria and fungi
Limitations of VTM
- Contaminant development may be noticed during the long transportation duration.
- Some viruses might be more labile than others, and the viral transport medium might be as effective.
- Some antimicrobials and chemicals used in viral transport medium might change the pH of the solution, which affects the viability of the virus.
- After transportation, the sample should be inoculated in the appropriate medium as soon as possible. For optimum results, the time-lapse between specimen collection and inoculum onto the culture medium should be reduced to the minimum.
Further Readings
- https://virologyj.biomedcentral.com/articles/10.1186/s12985-021-01525-z
- https://www.who.int/ihr/publications/Annex8.pdf?ua=1
- Johnson, F. B. (1990). Transport of viral specimens. Clinical microbiology reviews, 3(2), 120–131.
- https://doi.org/10.1128/cmr.3.2.120
- https://www.who.int/ihr/publications/Annex8.pdf?ua=1
- https://www.cdc.gov/coronavirus/2019-ncov/downloads/Viral-Transport-Medium.pdf
- https://academic.oup.com/labmed/article/52/2/e39/5998491f