Not necessarily. Impetigo can be caused by either staph (or antibiotic resistant staph called mrsa) or strep. In order to make sure that MRSA is not a cause of the infection, bacterial cultures may need to be done. Mrsa can cause severe infection because most antibiotics do not work. Overuse of antibiotics is a prime cause of antibiotic resistance. So be careful, not all infections require antibiotic treatment.
Not always. Mrsa is a drug resistant strain of staph. Impetigo is a superficial bacterial skin infection, which can be caused by run of the mill staph or mrsa. This is why it is generally important to culture the wound for properly targeted therapy.