What are macrolide antibiotics?

Quick Answer
Macrolide antibiotics are well-established, broad-spectrum, antibacterial agents derived from Streptomyces bacteria. Macrolides are a large, structurally diverse group of antibiotics composed of different-sized macrocyclic lactones attached to sugar moieties. Thebest-known macrolide antibiotic is erythromycin.Newer semisynthetic derivatives of erythromycin include azithromycin, clarithromycin, and dirithromycin. Macrolide antibiotics are especially useful as a treatment option for persons who are allergic to penicillin.
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Definition

Macrolide antibiotics are well-established, broad-spectrum, antibacterial agents derived from Streptomyces bacteria. Macrolides are a large, structurally diverse group of antibiotics composed of different-sized macrocyclic lactones attached to sugar moieties. The best-known macrolide antibiotic is erythromycin. Newer semisynthetic derivatives of erythromycin include azithromycin, clarithromycin, and dirithromycin. Macrolide antibiotics are especially useful as a treatment option for persons who are allergic to penicillin.

Mode of Action

Macrolide antibiotics are generally bacteriostatic agents that disrupt bacterial growth without causing cell death. These agents inhibit bacterial growth by suppressing protein synthesis. This mechanism occurs with the antibiotic reversibly binding to the 50S bacterial ribosomal subunit and inhibiting translocation by dissociating peptidyl-transfer ribonucleic acid (RNA) from the ribosome. This process prevents peptide chain elongation, cell growth, and reproduction. At high concentrations, macrolides have been known to exhibit bactericidal properties and cause cell death by interfering with deoxyribonucleic acid (DNA) replication.

Pharmacology

The pharmacological properties of an antibiotic dictate its effectiveness in inhibiting bacterial infections. Macrolides are typically administered orally but are generally poorly absorbed. Newer erythromycin derivatives exhibit broader activity and effectiveness against intracellular pathogens. Their most important attributes include improved lung and tissue absorption, higher intracellular concentrations and bioavailability, fewer dosing regimens, and less frequent drug-drug interactions.

Indications

Macrolides primarily display antibacterial activity toward most aerobic and anaerobic gram-positive bacteria with the exception of enterococci. Macrolides also inhibit some Mycoplasma species and anaerobic gram-negative pathogens. These antibiotics are effective in treating respiratory tract infections such as Legionnaires’ disease, community acquired pneumonia, pertussis (whooping cough), and diphtheria. Other indications include skin and soft tissue infections and sexually transmitted diseases, including chlamydia, syphilis, and gonorrhea. Macrolides also are potent against Helicobacter pylori infections of the stomach, penicillin-resistant staphylococcal infections, and group A streptococcal and pneumococcal infections in persons allergic to penicillin. Macrolides are not recommended for the treatment of meningitis.

Side Effects

Macrolides are considered one of the safest and best tolerated classes of antibiotics, even in children. The most common side effects include gastrointestinal upsets such as abdominal pain, dyspepsia (indigestion), diarrhea, nausea, and vomiting. More serious side effects can occur depending on the prescribed antibiotic and include allergic and dermatologic reactions, hepatic (liver) dysfunction, drug-drug interactions, cardiac and ventricular arrhythmias, and dose-related complications such as tinnitus and hearing loss.

Impact

Macrolide antibiotics have been essential in the treatment of infectious diseases for many years. Their discovery has provided a safe alternate therapy option for persons with an allergy to penicillin, one of the most frequent causes of severe allergic drug reactions.

Bibliography

Kirst, Herbert A. “Antibiotics: Macrolides.” In Van Nostrand’s Encyclopedia of Chemistry, edited by Glenn D. Considine. 5th ed. Hoboken, N.J.: Wiley-Interscience, 2010.

Sanford, Jay P., et al. The Sanford Guide to Antimicrobial Therapy. 18th ed. Sperryville, Va.: Antimicrobial Therapy, 2010.

Schönfeld, W., and H. A. Kirst, eds. Macrolide Antibiotics. Boston: Birkhäuser, 2002.

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