Azithromycin is an antibiotic useful for the treatment of a number of bacterial infections.This includes middle ear infections, strep throat, pneumonia, traveler's diarrhea, and certain other intestinal infections.n 2010, azithromycin was the most prescribed antibiotic for outpatients in the US, whereas in Sweden where outpatient antibiotic use is a third as prevalent, macrolides are only on 3% of prescriptions.