Amies Transport Medium is an improved transport medium designed to prolong the viability of pathogenic organisms.
It contains charcoal, which helps maintain the viability of pathogens during transport.
The medium is semisolid and is recommended for use in qualitative procedures.
It is used specifically for transporting clinical swab specimens to the laboratory.
Amies Transport Medium is a modified version of Stuart’s Transport Medium.
The modification involves replacing glycerophosphate with an inorganic phosphate buffer.
Charcoal is added to the medium to enhance its performance.
This modified version (Amies Medium) has shown a higher percentage of positive results compared to Stuart’s Transport Medium.
Composition of Amies Transport Medium
Sodium chloride: 3.000 g/l
Potassium chloride: 0.200 g/l
Calcium chloride: 0.100 g/l
Magnesium chloride: 0.100 g/l
Monopotassium phosphate: 0.200 g/l
Disodium phosphate: 1.150 g/l
Sodium thioglycollate: 1.000 g/l
Charcoal: 10.000 g/l
Agar: 4.000 g/l
Final pH (at 25°C): 7.2 ± 0.2
Principle of Amies Transport Medium
Amies Transport Medium provides a reduced environment due to the presence of sodium thioglycollate and a small amount of agar.
Charcoal helps to neutralize materials that are toxic to sensitive pathogens like Neisseria gonorrhoeae.
Calcium, magnesium, potassium, and sodium salts support the survival of gonococcal cells.
These salts also help control the permeability of bacterial cells.
Phosphates in the medium act as buffers to maintain pH stability.
Preparation of Amies Transport Medium
Suspend 20 g of the medium in 1 litre of distilled water.
Bring the mixture to a boil to completely dissolve the agar.
Distribute the solution into small screwcap bottles, stirring continuously to keep the charcoal evenly suspended.
Screw down the caps firmly on the completely filled bottles.
Sterilize the bottles by autoclaving at 121°C for 15 minutes.
Invert the bottles while cooling to ensure uniform distribution of charcoal.
Store the prepared bottles in a cool place until use.
Use sterile, cotton-tipped swabs on wooden sticks to collect the specimen.
Insert the swab into the medium, pushing it down to one-third of the medium depth.
Cut the stick so that when the cap is screwed down, the swab is forced to the bottom of the medium.
Ensure the cap is tightly closed and keep the bottle cool during the transport period.
Result Interpretation on Amies Transport Medium
Organisms Growth
Escherichia coli: Good recovery on subculture.
Klebsiella pneumoniae: Good recovery on subculture.
Neisseria meningitidis: Good recovery on subculture.
Pseudomonas aeruginosa: Good recovery on subculture.
Salmonella Typhi: Good recovery on subculture.
Shigella flexneri: Good recovery on subculture.
Staphylococcus aureus subsp. aureus: Good recovery on subculture.
Vibrio cholerae: Good recovery on subculture.
Bacteroides fragilis: Good recovery on subculture.
Haemophilus influenzae: Good recovery on subculture.
Neisseria gonorrhoeae: Good recovery on subculture.
Streptococcus pyogenes: Good recovery on subculture.
Uses of Amies Transport Medium
It is used for collecting, transporting, and preserving microbiological specimens.
It is formulated to maintain the viability of microorganisms without significant growth, as it is nonnutritive, phosphate-buffered, and semisolid.
It is a transport medium used to preserve the viability of anaerobes such as Neisseria gonorrhoeae and other pathogens from swabs.
It is used for the preservation of microbiological specimens.
It is recommended for throat, vaginal, and wound samples.
Limitations of Amies Transport Medium
The old medium should be freshly steamed and the charcoal resuspended before use.
Some growth of contaminants may occur during long periods of transport.
After transportation, the specimen should be inoculated onto the proper medium as soon as possible.
For optimum results, the time lapse between sample collection and inoculation onto culture medium should be minimized.
It may not be suitable for the transport of fastidious organisms.
Gonococci survive well in Amies Transport Medium for at least 6 to 12 hours if not exposed to temperature extremes.
By 24 hours, the number of gonococci may decrease significantly, potentially preventing recovery if only small numbers were initially present in the specimen.
References
HiMedia Laboratories – Technical Data Sheet for Amies Transport Medium
Oxoid – Product Details for Amies Transport Medium (CM0425)
Thermo Fisher Scientific – Instructions for Use (IFU60060)
Condalab – Product Datasheet for Amies Medium with Charcoal (1535)
SRL Chemicals – Product Details for Amies Transport Medium with Charcoal
