Erythromycin is a macrolide
The macrolides are a group of drugs whose activity stems from the presence of a macrolide ring, a large macrocyclic lactone ring to which one or more deoxy sugars, usually cladinose and desosamine, may be attached. The lactone rings are usually 14-, 15-, or 16-membered...

An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

 that has an antimicrobial spectrum similar to or slightly wider than that of penicillin
Penicillin is a group of antibiotics derived from Penicillium fungi. They include penicillin G, procaine penicillin, benzathine penicillin, and penicillin V....

, and is often used for people who have an allergy
An Allergy is a hypersensitivity disorder of the immune system. Allergic reactions occur when a person's immune system reacts to normally harmless substances in the environment. A substance that causes a reaction is called an allergen. These reactions are acquired, predictable, and rapid...

 to penicillins. For respiratory tract infections, it has better coverage of atypical organisms, including mycoplasma
Mycoplasma refers to a genus of bacteria that lack a cell wall. Without a cell wall, they are unaffected by many common antibiotics such as penicillin or other beta-lactam antibiotics that target cell wall synthesis. They can be parasitic or saprotrophic. Several species are pathogenic in humans,...

 and Legionellosis
Legionellosis is a potentially fatal infectious disease caused by gram negative, aerobic bacteria belonging to the genus Legionella. Over 90% of legionellosis cases are caused by Legionella pneumophila, a ubiquitous aquatic organism that thrives in temperatures between , with an optimum temperature...

. It was first marketed by Eli Lilly and Company
Eli Lilly and Company
Eli Lilly and Company is a global pharmaceutical company. Eli Lilly's global headquarters is located in Indianapolis, Indiana, in the United States...

, and it is today commonly known as EES (erythromycin ethylsuccinate, an ester prodrug
A prodrug is a pharmacological substance administered in an inactive form. Once administered, the prodrug is metabolised in vivo into an active metabolite, a process termed bioactivation. The rationale behind the use of a prodrug is generally for absorption, distribution, metabolism, and...

 that is commonly administered).

In structure, this macrocyclic compound contains a 14-membered lactone
In chemistry, a lactone is a cyclic ester which can be seen as the condensation product of an alcohol group -OH and a carboxylic acid group -COOH in the same molecule...

 ring with ten asymmetric centers and two sugars (L-cladinose
Cladinose is a hexose deoxy sugar that in several antibiotics is attached to the macrolide ring.In ketolides, a relatively new class of antibiotics, the cladinose is replaced with a keto group.-External links:* *...

 and D-desosamine
Desosamine is a 3--3,4,6-trideoxyhexose found in certain macrolide antibiotics such as the commonly prescribed erythromycin.-Biosynthesis:Six enzymes are required for its biosynthesis from TDP-glucose in Streptomyces venezuelae....

), making it a compound very difficult to produce via synthetic methods.

Erythromycin is produced from a strain of the actinomycete Saccharopolyspora erythraea
Saccharopolyspora erythraea
Saccharopolyspora erythraea, formerly known as Streptomyces erythraeus, is a species of actinomycete bacteria within the genus Saccharopolyspora.Saccharopolyspora erythraea is known for the production of the macrolide antibiotic erythromycin...

Abelardo Aguilar, a Filipino scientist, sent some soil samples to his employer Eli Lilly
Eli Lilly and Company
Eli Lilly and Company is a global pharmaceutical company. Eli Lilly's global headquarters is located in Indianapolis, Indiana, in the United States...

 in 1949.