Final answer:
A school nurse might suspect impetigo if they observe vesicles, pustules, or bullae around the nose and mouth which rupture to become encrusted sores, often with a yellowish crust and draining exudate, characteristic of this highly contagious skin infection commonly caused by Staphylococcus aureus or Streptococcus pyogenes.
Step-by-step explanation:
The skin infection impetigo is characterized by certain visual signs that a school nurse can identify. Suspected cases of impetigo show vesicles, pustules, and sometimes bullae, which are large, fluid-filled blisters. These often appear around the nose and mouth. In nonbullous impetigo, which is more common, these vesicles and pustules burst and become crusted sores, often with a yellowish crust and exudate draining from the lesion. In bullous impetigo, the bullae rupture leading to larger draining, encrusted sores.
Given that impetigo is highly contagious and commonly seen in children, it is crucial to diagnose and treat it early. It is usually caused by bacterial infection, typically Staphylococcus aureus, Streptococcus pyogenes, or a combination of both. In examining a child, if a school nurse observes these symptoms, especially around the nose and mouth, they would suspect impetigo and should advise further medical evaluation and treatment.