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.zithromycin is used to treat many different infections, including: 1  Prevention and treatment of acute bacterial exacerbations of chronic obstructive pulmonary disease due to H. influenzae, M. catarrhalis, or S. pneumoniae.