VTM: Introduction, Composition, Preparation, Uses, and Keynotes

Introduction of VTM

VTM stands for viral transport medium. It is the medium for the storage and transportation of viruses. It does not only preserve viral infectivity within the specimen but also prevents the specimen from drying as well as prevents the growth of other microbes like bacteria and fungi.

Composition of Viral Transport Medium(VTM)

Ingredients	Amount/Volume
Hanks Balanced Salt Solution (HBSS)	500 ml
Fetal bovine serum (FBS)	10 mL
Gentamicin sulfate	50 mg/mL
Amphotericin B	250 µg/mL
Indicator	Optional (if yes HBSS with phenol red can be used)

VTM Preparation Requirements

• Laminar air flow (LAF) chamber/biosafety cabinet (BSC)
• Heat activated Fetal Bovine Serum (FBS)
• Sterile wrapped pipettes
• Sterile conical tubes
• 0.20µm to 0.45µm filter unit
• Cell spreader or equivalent
• Labels
• Sterile HBSS with calcium and magnesium ions, with or without phenol red (a pH indicator), 500mL bottle
• Gentamicin sulfate (50mg/mL) or similar antibiotic at an appropriate concentration to prevent bacterial contamination and growth
• Amphotericin B (250µg/mL) or similar antifungal at an appropriate concentration to prevent fungal contamination and growth
• 70% ethanol (disinfectant)

Preparation of VTM

• Perform in laminar air flow (LAF) chamber or biosafety cabinet (BSC).
• Clean work surface with 70% ethanol.
• Disinfect reagent bottles before placing on work surface.
• Remove plastic seal and loosen lid on a 500 mL bottle of sterile HBSS.
• Using a sterile pipette, aseptically add 10 mL of the inactivated FBS to the bottle of HBSS.
• Using a sterile pipette, aseptically add 2 mL of the Gentamicin/Amphotericin B mixture from the Antibiotics.
• This results in final concentrations of 100 µg/mL for Gentamicin and 0.5µg/mL for Amphotericin B.
• Cap the bottle securely and mix thoroughly by inverting the bottle.
• Store at 2-8°C until dispensed into aliquots.
• Aliquot 3 mL of prepared VTM into individual sterile conical screwcapped tubes (such as a 16×100 mm tubes). Keep lids tightly closed after medium is dispensed and label each tube.
• Store at 2-8°C (or temperature determined by specific data generated in stability study by manufacturing laboratory).
• Expires: Insert date 1 year after the manufacture date.

Uses of Viral Transport Medium

1. VTM preserves viral infectivity within the specimen.
2. It prevents specimen from drying.
3. It Prevents growth of bacteria and fungi.

Keynotes

• As sterile solutions, Gentamicin and Amphotericin B can be obtained. If only sterile solutions are utilized, the filtration steps in this operation can be skipped if each of these components is handled aseptcally and sterility is maintained for each component.
• Hanks balanced Salt Solution (HBSS) is available in both forms of with or without indicator (phenol red).
• Fetal bovine serum (FBS) is available in both forms of heat inactivated and heat activated FBS.
• Heat-inctivated FBS may lengthen the procedure of VTM preparation.

Further Readings

1. https://virologyj.biomedcentral.com/articles/10.1186/s12985-021-01525-z
2. https://www.who.int/ihr/publications/Annex8.pdf?ua=1
3. Johnson, F. B. (1990). Transport of viral specimens. Clinical microbiology reviews, 3(2), 120–131.
4. https://doi.org/10.1128/cmr.3.2.120
5. https://www.cdc.gov/coronavirus/2019-ncov/downloads/Viral-Transport-Medium.pdf
6. https://www.who.int/ihr/publications/Annex8.pdf?ua=1
7. https://www.cdc.gov/coronavirus/2019-ncov/downloads/Viral-Transport-Medium.pdf
8. https://academic.oup.com/labmed/article/52/2/e39/5998491f