Tetracycline antibiotics

Tetracycline antibiotics are a class of antibiotics that are used to treat a wide variety of infections. They are derived from the bacterium Streptomyces and are characterized by their four-ring molecular structure.

Structure

Numbering of the tetracycline structure.

Tetracyclines are defined by their four hydrocarbon rings, which are fused together. The basic structure of tetracyclines allows for various modifications, leading to different derivatives with varying properties and spectrum of activity.

Mechanism of Action

Tetracyclines work by inhibiting protein synthesis in bacteria. They bind to the 30S ribosomal subunit, preventing the attachment of aminoacyl-tRNA to the ribosome and thus inhibiting the addition of new amino acids to the growing peptide chain. This action is generally bacteriostatic, meaning it inhibits the growth and reproduction of bacteria rather than killing them outright.

Spectrum of Activity

Tetracyclines are broad-spectrum antibiotics, effective against a wide range of Gram-positive and Gram-negative bacteria. They are also active against certain intracellular pathogens such as Chlamydia, Mycoplasma, and Rickettsia.

Clinical Uses

Tetracyclines are used to treat various infections, including:

• Respiratory tract infections
• Urinary tract infections
• Acne vulgaris
• Cholera
• Lyme disease
• Rocky Mountain spotted fever

Side Effects

Common side effects of tetracyclines include gastrointestinal disturbances, such as nausea and diarrhea. They can also cause photosensitivity, leading to an increased risk of sunburn. Tetracyclines can affect bone and tooth development, so they are generally avoided in children under the age of 8 and in pregnant women.

Resistance

Bacterial resistance to tetracyclines can occur through several mechanisms, including efflux pumps that expel the drug from the cell, ribosomal protection proteins that prevent tetracycline binding, and enzymatic inactivation of the drug.

Derivatives

Several derivatives of tetracycline have been developed to overcome resistance and improve pharmacokinetic properties. These include doxycycline and minocycline, which have improved absorption and longer half-lives compared to the original tetracycline.

Related pages

• Antibiotic resistance
• Protein synthesis inhibitors
• Streptomyces