Definition of transport medium
Transport media are special media formulated to preserve a specimen and minimize bacterial overgrowth from the time of collection to the time it is received at the laboratory to be processed. Depending on the type of organisms suspected in the sample, transport media may vary. However in general, transport media are classified on the basis of physical state as semi solid and liquid and also in basis of their utility as bacterial or viral transport media. Transport media contains only buffers and salt instead of containing any nutritional ingredients such as carbon, nitrogen, and organic growth factors so as to prevent microbial multiplication. Addition of antibiotics and other substances like glycerol may be added for transporting specimens for tissue culture.
Classification of commonly used transport mediums
1. Amies Medium With Charcoal: Charcoal helps eliminate metabolic products of bacterial growth, which may be especially useful in the isolation of fastidious organisms like However it is suggested that, some other pathogens like Campylobacter can also survive in such medium. Amies Transport Medium with charcoal is used for transportation and preservation of microbiological specimen.
2. Amies Medium Without Charcoal: is used for collecting, transporting and preserving microbiological specimens. It is formulated to maintain the viability of microorganisms without significant increase in growth, being nonnutritive, phosphate buffered and semi-solid.
3. Cary and Blair Medium: semi-solid, white colored transport medium for faeces that may contain Salmonella, Shigella, Vibrio or Campylobacter. Cary and Blair Transport Medium is used for collecting, transporting and preserving microbiological specimens, particularly those containing Vibrio cholerae.
4. Stuarts Medium: Commonly used for transporting specimens suspected of having gonococci. Also used for transporting Throat, vaginal, wound and skin swabs that may contain fastidious organisms.
