Final answer:
The first line treatment for impetigo with fewer than five lesions of 1-2 cm in diameter on the legs of a nine year old girl is topical mupirocin.
Step-by-step explanation:
The first line treatment for impetigo with fewer than five lesions of 1-2 cm in diameter on the legs of a nine year old girl is topical mupirocin. Impetigo is a skin infection caused by Staphylococcus aureus or Streptococcus pyogenes. Topical mupirocin is an antibiotic ointment that is effective in treating impetigo. It is applied directly to the affected area and helps eliminate the bacteria causing the infection.