Which antibiotics are generally used to treat impetigo?

Depends. Most impetigo are caused by staph, and responds to Mupirocin ointment. However, if unresponsive, your doctor will culture the area and prescribe the appropriate antibiotic.
Impetigo. Antibiotics are the mainstay of conventional therapy. Topical anti-microbial ointments are often effective for staph impetigo, and treatments such as bactroban (mupirocin) ointment are commonly used. Oral antibiotics such as Keflex (cephalexin) - or Bactrim (sulfamethoxazole and trimethoprim) (septra) are used if there are concerns about methicillin-resistant-staph (mrsa).