Final answer:
The nurse should place the specimens into plastic biohazard bags when transporting them, in addition to following standard safety protocols such as wearing gloves and potentially a gown.
Step-by-step explanation:
When transporting blood, urine, and stool specimens of a client with meningococcal meningitis, a nurse should take several precautions due to the highly infectious nature of the bacterium Neisseria meningitidis. The correct precaution the nurse should take is to place the specimens into plastic biohazard bags. This is crucial for containing any potential infectious agents and preventing the spread of the disease to healthcare workers and the environment. Additionally, the nurse should adhere to standard safety protocols which often include wearing gloves and sometimes a gown to protect against the risk of exposure to infectious agents, especially when handling and transporting specimens.