Final answer:
Specimens requiring preservation during transport are best maintained in Amies transport medium with charcoal, which mitigates the effect of toxic bacterial metabolites by binding them to charcoal.
Step-by-step explanation:
Specimens should be transported in Amies transport medium with charcoal when there's a delay between collection of the specimen and its culture. This medium is designed to preserve bacteria during transport, particularly in situations where there might be toxic metabolites produced as bacteria can bind to the charcoal, allowing for better survival rates of the specimens. Among the available options for transporting specimens, Amies transport medium with charcoal is particularly suitable for specimens that are not immediately inoculated onto culture media.