What is Transport Media?
Transport media are basically buffer solutions that contain carbohydrate, peptones, along with other nutritional elements (excluding growing factors) that are designed to protect the health of bacteria during transport, without allowing for their multiplicity. The main goal of utilization of the medium is to keep the sample as close to its original condition as is possible.
The goal of the transport medium is to protect a specimen and limit bacterial overgrowth starting from the moment of collection through the treatment of the sample. Based on the type of organisms found in the sample, the transport mediums can differ.
In general, media for transport are classified based on the physical state of their materials as semi-solid or liquid, and in relation to their effectiveness as viral or bacterial transport media.
What does transport media contain?
- Only buffers and salts are included.
- Does not contain any nutrients like nitrogen, carbon as well as organic growth stimulants, so that it can prevent the multiplication of microbial species.
- In addition, antibiotics and other compounds like glycerol could be used to transport tissues for culture.
What samples are collected in transport medium?
Every kind of sample may have pathogens but that can not be processed in a timely manner need transport medium. It could be stool, urethral swabs throat and nasal swabs, and samples for tissue culture and so on.
What are the commonly used Transport media?
Here are a few instances of transportation mediums and their intended purpose:
- Cary and Blair Medium: semi-solid colored transport material for human feces which could be contaminated with Salmonella, Shigella, Vibrio or Campylobacter.
- Amies medium with charcoal: Charcoal aids in the elimination of metabolic substances that are produced by bacterial growth which can be particularly useful in the identification of fastidious organisms. However, it is recommended that other pathogens such as Campylobacter are also able to survive in this type of medium.
- Amies medium without charcoal: Ideal for isolation of Mycoplasma and Ureaplasma.
- Stuarts medium: Stuarts medium is commonly used to transport specimens that are that are suspected to have gonococci. It is also used to transport wound, throat and skin Swabs that may contain fastidious bacteria.
- Venkatraman Ramakrishnan (VR) medium: It is used to move feces of suspected patients with cholera.
- Sach’s buffered glycerol saline: It is used to move the feces of patients who are believed to have dysentery caused by bacillary bacteria.
- Viral Transport Medium: Viral Transport Medium (VTM) is perfect for diagnosing viral infections. Ocular or respiratory as well as tissue samples can be placed to this medium. The fluid samples, like tracheal wash samples or peritoneal fluid must be submitted in their original form in sterile vials that stop the desiccation. If there is no viral transport medium, place Swabs in sealed, sterile vials that have a few drops saline to avoid the desiccation process from occurring. Wood-handled, plastic, cotton and dacron as well as other synthetic swabs are acceptable. Swabs made of calcium alginate should be avoided. The transport media of bacteria are not suitable for research in virology.
- Anaerobic Transport Medium (ATM): It is a mineral salt-based semi-solid media that contains reduction agents that are designed to be an absorbing medium to maintain the viability of anaerobic microbes. It is composed of buffered mineral salts in a semi-solid medium with cysteine and sodium thioglycolate as reducing agents to provide a safe environmental. Resazurin can also be used to act as a signal for redox in order to detect exposure to oxygen by changing to pink. It creates an atmosphere, that ensures the viability of the majority of microorganisms, without massive multiplication, and permits reduction of inhibitors found in clinical materials. Examples include thioglycollate-based broth.