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 is 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.
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 to transport 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 specimens 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|
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, 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:
- Add 10g veal infusion broth and 2g bovine albumin fraction V to sterile distilled water (to 400 mL)
- Add 0.8mL gentamicin sulfate solution (50mg/mL) and 3.2 mL amphotericin B (250μg/mL)
- 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 frozen at -70 °C or colder once in the laboratory.
Reference and further reading