Tetracycline

This article deals with the specific antibiotic called tetracycline. For the group of antibiotics known as the tetracyclines, see tetracycline antibiotics.

Tetracycline (INN) is a broad-spectrum polyketide antibiotic produced by the Streptomyces genus of Actinobacteria, indicated for use against many bacterial infections. It is commonly used to treat acne. It is sold under the brand names Sumycin, Terramycin, Tetracyn, and Panmycin, among others. Actisite is a thread-like fiber form, used in dental applications. It is also used to produce several semi-synthetic derivatives, which together are known as the tetracycline antibiotics.

Mode of action

It works by inhibiting action of the prokaryotic 30S ribosome, by binding the 16S rRNA thereby blocking the aminoacyl-tRNA. However, bacteria strains can acquire resistance against tetracycline and its derivates by encoding a resistance operon. In eukaryotic cells, toxicity may be the result of inactivation of mitochondrial 30S ribosomes.

History

The tetracyclines are a large family of antibiotics that were discovered as natural products by Benjamin Minge Duggar and first described in 1948. Tetracycline was then discovered by Lloyd Conover in the research departments of Pfizer. The patent for tetracycline, , was first issued in 1950. However, Nubian mummies have been studied in the 1990s and were found to contain significant levels of tetracycline; there is evidence that the beer brewed at the time could have been the source. Tetracycline sparked the development of many chemically altered antibiotics and in doing so has proved to be one of the most important discoveries made in the field of antibiotics. It is used to treat many gram-positive and gram-negative bacteria and some protozoa. It, like some other antibiotics, is also used in the treatment of acne.

Cautions, contraindications, side effects

Are as those of the tetracycline antibiotics group:

• Can stain developing teeth (even when taken by the mother during pregnancy)
• Inactivated by Ca²⁺ ion, not to be taken with milk or yogurt
• Inactivated by aluminium, iron and zinc, not to be taken at the same time as indigestion remedies
• Inactivated by common antacids and over-the-counter heartburn medicines.
• Skin photosensitivity; exposure to the Sun or intense light is not recommended
• Drug-induced lupus, and hepatitis
• Tinnitus
• When used for acne vulgaris, skin can be extremely dry and flaky if overused
• May interfere with methotrexate by displacing it from the various protein binding sites

Indication

Tetracycline's primary use is for the treatment of acne vulgaris and rosacea.

It is also used to treat a very wide range of infections; see tetracycline antibiotics for details.

Other uses

Since tetracycline is absorbed into bone, it is used as a marker of bone growth for biopsies in humans, and as a biomarker in wildlife to detect consumption of medicine- or vaccine-containing baits. The presence of tetracycline in bone is detected by its fluorescence.

In genetic engineering tetracycline is used in transcriptional activation. Tetracycline is also one of the antibiotics used to treat ulcers caused by bacterial infections. In cancer research at Harvard Medical School, tetracycline has been used to reliably cause regression of advanced stages of leukemia in mice, by putting this inexpensive antibiotic into their drinking water.

Cell Culture

Tetracycline is used in cell biology as selective agent in cell culture systems. It is toxic to prokaryotic and eukaryotic cells and selects for cells harboring the bacterial tet^r gene, which encodes a 399-amino acid membrane associated protein. This protein actively exports tetracycline out of the cell rendering cells harboring this gene more resistant to the drug. The yellow crystalline powder can be dissolved in water (20mg/ml) or ethanol (5mg/ml) and is routinely used at 10mg/L in cell culture. In cell culture at 37^oCelsius it is stable for 4 days.

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