antimicrobial spectrum as erythromycin , but is more effective against certain Gram-negative bacteria, particularly Haemophilus influenzae . Azithromycin resistance has been described [5] and is endemic in many areas. Azithromycin has been most effective against isolates of the following microorganisms: Staphylococcus aureus Streptococcus agalactiae Streptococcus pneumoniae Streptococcus pyogenes Haemophilus ducreyi Haemophilus