Viral Transport Media (VTM): Preparation and Uses

Viral Transport Media (VTM) are suitable for collection, transport, maintenance and long-term freeze storage of clinical specimens containing viruses, chlamydia, mycoplasma or ureaplasma organisms. It maintains organism viability for 48 hours at room or refrigerated temperature.

Commercially prepared VTM are available in a plastic, screw cap tube that contains buffered protein (serum, albumins, or gelatin) and antibiotics. Antibiotics are usually incorporated in viral transport media to suppress the growth of contaminating bacteria and fungi, so separate specimens from the same site must be collected if bacterial or fungal cultures are also requested.

Viral Transport Medium (VTM)

Features of Viral Transport Medium (VTM)

  • Sustains viability for culture and nucleic acid amplification test (NAAT) of viruses, chlamydiae, mycoplasmas and ureaplasmas in a single formulation by “preserving” and “stabilizing” them
  • Prevents specimen drying
  • Offers flexibility in transport temperature ranges–room temperature or refrigerated.
  • Suppresses bacterial and fungal contamination by incorporating antibiotics in the medium.
  • Preserves viruses and chlamydiae for long-term frozen storage.

Use of Viral Transport Medium (VTM)

Liquid specimens such as CSF, bronchoalveolar lavage fluid, or urine should not be diluted in viral transport media.

Viral Transport Media (VTM) is used for the transport of the following specimens

Body Sites Potential Viruses Specimen Collection
Eye Adenovirus, enterovirus, coxsackievirus A, cytomegalovirus (CMV), herpes simplex virus (HSV), varicella-zoster virus (VZV) Collect conjunctival swab on Dacron or rayon swab moistened with saline and place in VTM; aqueous and vitreous fluid placed in a sterile container without VTM.
Feces Adenovirus, astrovirus, CMV, norovirus, rotavirus Fecal specimens (preferred) in a leak-proof container; fecal swabs in VTM
Genital Adenovirus, CMV, HSV, papillomavirus, varicella-zoster virus (VZV) Collect on swabs and transport in VTM
Respiratory Adenovirus, coronavirus, hantavirus, CMV, HSV, influenza virus, parainfluenza virus, metapneumovirus, measles virus, rhinovirus, RSV, VZV Nasopharyngeal aspirates (NPA) are specimen of choice from children, NPA or nasopharyngeal swabs collected from adults; bronchoalveolar lavage for the diagnosis of lower respiratory tract infections. Swabs are transported in VTM.
Skin Adenovirus, enterovirus, HHV6, HHV8, HSV, measles virus, parvovirus B19, poxvirus, rubella virus, VZV Swab or aspirate fluid in vesicle and scrape cells at the base of the lesion; place fluid in VTM
Tissue Adenovirus, CMV, HSV, other viruses Place in VTM

Preparation

Commercially prepared Viral Transport Media (VTM) are available in the market but VTM can also be prepared locally. It is available in 1 mL or 3 mL vials in a flat-bottomed conical tube along with regular polyester-tipped swabs and a flexible minitip flocked swab (plastic or wire).

A suitable VTM for use in collecting throat and nasal swabs from human patients is prepared as follows:

  1. Add 10g veal infusion broth and 2g bovine albumin fraction V to sterile distilled water (to 400 mL)
  2. Add 0.8mL gentamicin sulfate solution (50mg/mL) and 3.2 mL amphotericin B (250μg/mL)
  3. Sterilize by filtration

Collection and Transport

After sample collection, VTM can be stored at 2-25 °C and processed within 48 hours. If delivery and processing exceed 48 hours, specimens should be transported in dry ice and once in the laboratory frozen at -70 °C or colder.

Reference and further reading

About Acharya Tankeshwar 426 Articles
Hello, thank you for visiting my blog. I am Tankeshwar Acharya. Blogging is my passion. I am working as an Asst. Professor and Microbiologist at Department of Microbiology and Immunology, Patan Academy of Health Sciences, Nepal. If you want me to write about any posts that you found confusing/difficult, please mention in the comments below.

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