Macrolide: One in a class of antibiotics that includes Biaxin (Clarithromycin), Zithromax (Azithromycin), Dificid (Fidoximycin), and Erythromycin.
The macrolides inhibit the growth of bacteria and are often prescribed to treat rather common bacterial infections.
In more technical terms, the macrolides are a group of antibiotics produced by various strains of Streptomyces (spore forming bacteria that grow slowly in soil or water as a branching filamentous mycelium similar to that of fungi) and have a complex chemical (macrocyclic) structure. They act by inhibiting protein synthesis, specifically by blocking the 50S ribosomal subunit. They are broad spectrum antibiotics.