Final answer:
The nurse would instruct the parents to discard the child's toothbrush last in the case of a group A streptococcal infection.
Step-by-step explanation:
The nurse would instruct the parents to discard the child's toothbrush last.
When a child has a group A streptococcal infection, it is important to replace their toothbrush after starting antibiotic treatment to prevent re-infection. However, this step should be done after using a cool mist humidifier, encouraging the child to drink liquids, and giving the full course of antibiotics.