In microbiology laboratories, collecting a specimen is only the first step in obtaining accurate results. The state of the sample during the transport is also important. When a specimen is required to be transported from the collection site to the laboratory, the viability of the microorganisms may be reduced by exposure to unsuitable conditions. This can affect culture recovery and lead to inaccurate findings. To avoid this problem, laboratories use transport media which maintain the condition of microorganisms until they can be processed. Amies Transport Medium is a standard medium for this purpose. Due to its simple formulation and reliable performance, it is a commonly used medium in the clinical and diagnostic laboratory for the transportation of swab samples.
Amies Transport Medium is a semi-solid transport medium used for collection, transportation and storage of bacteriological specimens. It is designed for use in preserving the viability of microorganisms during transport, without allowing significant growth. The medium was formulated by modifying Stuart’s medium, with changes facilitating the survival of some fastidious organisms. In this formulation, glycerophosphate was substituted by an inorganic phosphate buffer and charcoal was added, for enhancing the recovery of sensitive pathogens. Since survival of microorganisms is affected by transport conditions, amies transport medium can be considered a good medium to reduce harmful changes until specimens can be cultured on suitable media.
The amies transport medium principle is based on preserving microorganisms during transportation. Sodium thioglycollate creates a reduced environment that helps protect sensitive organisms, while the low agar concentration provides a semi-solid consistency that stabilizes the specimen during transport.
Charcoal absorbs toxic substances which might be released from the swab or the specimen and are harmful to the sensitive organisms such as Neisseria gonorrhoeae. Calcium, magnesium, sodium, and potassium salts contribute to bacterial survival, while phosphate salts are responsible for stable pH during transportation.
In standard laboratory use, both charcoal and non-charcoal formulations are employed according to the needs of the test. Although both allow survival of microorganisms during transport, the use of charcoal-conataining formulation is usually recommended for recovery of fastidious organisms. For molecular testing such as PCR, the non-charcoal formulation is generally recommended as charcoal may inhibit DNA extraction processes.
To ensure reliable performance, standard preparation procedures should be followed.
Like other microbiological media, amies transport medium is evaluated against defined quality parameters before use. The dehydrated medium appears as a grey to black free-flowing powder, while the prepared medium forms a black opaque gel in tubes. The pH was adjusted to 7.2 ± 0.2 to help in preservation of the specimen during transport. Consistent medium performance and reliable quality during specimen transport can be achieved with routine quality control.
Amies Transport Medium is not intended to promote visible growth of microorganisms during transport but to keep the organisms viable until processing in the laboratory. After transport, specimens are inoculated onto appropriate culture media such as Soyabean Casein Digest Agar and observed for isolation of the expected organisms. Successful recovery indicates that the transport conditions and medium have adequately preserved the specimen.
The medium has been demonstrated to maintain a broad spectrum of clinically relevant organisms like gram positive and gram negative bacteria after transport making it appropriate for routine diagnostics applications.
Amies Transport Medium is used when specimens cannot be processed immediately after collection. Common applications include:
Reliable quality transport media is required to maintain specimen integrity until it reaches the laboratory. Amies Transport Medium (TM 009) from TM Media is produced under controlled quality to meet the needs of routine microbiological testing requirements.
Its formulation helps laboratories maintain sample integrity from collection through processing.
The success of a microbiology result is dependent on how well the specimen was preserved before beginning any laboratory testing. Its semi-solid formulation, buffering system, reducing agents, and charcoal content provide a good protection for clinical samples during transport to the laboratory. Therefore, the modification of the Stuart transport medium by Amies has become an essential part of modern specimen transport techniques. Amies Transport Medium is a valuable medium for preservation of bacteriological samples in clinical and diagnostic routine application during transportation.
A. To establish a reduced environment.
A. No, this is a specialized medium for the transport of bacteriological samples.
A. No
A. Viable organisms are necessary to culture, identify and perform further microbiological testing.
A. Although this medium may help in organisms’ survival, prolonged storage may continuously decrease the number of viable microorganisms.
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