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Oxytetracycline is a broad-spectrum tetracycline antibiotic, the second of the group to be discovered.
Oxytetracycline works by interfering with the ability of bacteria to produce essential proteins. Without these proteins, the bacteria cannot grow, multiply and increase in numbers. Oxytetracycline therefore stops the spread of the infection, and the remaining bacteria are killed by the immune system or eventually die.
Oxytetracycline is active against a wide variety of bacteria. However, some strains of bacteria have developed resistance to this antibiotic, which has reduced its effectiveness for treating some types of infections.
Oxytetracycline is used to treat infections caused by Chlamydia, such as psittacosis, trachoma, and urethritis, and infections caused by Mycoplasma organisms, such as pneumonia.
Oxytetracycline is used to treat acne, due to its activity against the bacteria on the skin that influence the development of acne ( Cutibacterium acnes). It is used to treat flare-ups of chronic bronchitis, due to its activity against Haemophilus influenzae. Oxytetracycline may be used to treat other rarer infections, such as those caused by a group of microorganisms called rickettsiae (e.g., Rocky Mountain spotted fever). To make sure the bacteria causing an infection are susceptible to it, a tissue sample is usually taken; for example, a swab from the infected area or a urine or blood sample.
Oxytetracycline was patented in 1949 and came into commercial use in 1950. It is on the World Health Organization's List of Essential Medicines as an alternative to tetracycline.
It is sometimes used to treat spirochaetal infections, clostridial wound infection, and anthrax in patients sensitive to penicillin. Oxytetracycline is used to treat infections of the respiratory and urinary tracts, skin, ear, eye and gonorrhoea, although its use for such purposes has declined in recent years due to large increases in bacterial resistance to this class of drugs. The drug is particularly useful when penicillins and/or cannot be used due to allergy. It may be used to treat Legionnaires' disease as a substitute for a macrolide or quinolones.
Oxytetracycline is especially valuable in treating nonspecific urethritis, Lyme disease, brucellosis, cholera, typhus, tularaemia, and infections caused by Chlamydia, Mycoplasma, and Rickettsia. Doxycycline is now preferred to oxytetracycline for many of these indications because it has improved pharmacologic features.
The standard dose is 250 to 500 mg every six hours by mouth. In particularly severe infections, this dose may be increased accordingly. Occasionally, oxytetracycline is given by intramuscular injection or in the form of creams, ophthalmic , or eye drops.
The biosynthesis of oxytetracycline begins with the utilization of PKS enzymes ketosynthase (KS), the chain length factor (CLF), the acyl carrier protein (ACP), and an acyltransferase (encoded as OxyA, OxyB, OxyC and OxyP in the oxytetracycline gene cluster) to catalysis the extension of the malonamyl-CoA starting unit with eight malonyl-CoA extender units. The process of elongating the polypeptide skeleton occurs through a series of Claisen-like decarboxylation reactions until the linear tetracyclic skeleton is formed. Thus, minimal PKSs form a completed Amide polyketide backbone without any additional post-synthase tailoring enzymes (Figure 1).
Following the formation of the linear tetracyclic skeleton, four successive cyclization reactions must occur in a regioselective manner to produce the aromatic natural product known as pretetramid, a common precursor to both oxytetracycline and other tetracycline antibiotics. In the oxytetracycline gene cluster, these enzymes are encoded as OxyK (aromatase), OxyN (cyclase), and OxyI (cyclase). Formation of pretetramid allows for one of the most important intermediates en route to the biosynthesis of oxytetracycline; this is the generation of anhydrotetracycline. "Anhydrotetracycline". Anhydrotetracycline contains the first functionalized A ring in this biosynthetic pathway.
After the formation of anhydrotetracycline, ATC monooxygenase ( OxyS) the C-6 position in an enantioselective manner in the presence of the cofactor NADPH and atmospheric oxygen to produce 5a,11a-dehydrotetracycline. Next, a hydroxylation occurs at the C-5 position of 5a,11a-dehydrotetracycline via the oxygenase encoded as OxyE in the oxytetracycline gene cluster. This produces the intermediate 5a,11a-dehydro-oxytetracycline. However, the exact mechanism of this step remains unclear. The final step of this biosynthesis occurs through the reduction of a double bond in the Enone of 5a,11a-dehydro-oxytetracycline. In this final step, the cofactor NADPH is employed by TchA (reductase) as the reducing agent. Upon reduction, the enol form is favored due to conjugation, thus producing the aromatic polyketide oxytetracycline. Figure 2 shows the biosynthesis as described above, as well as an arrow-pushing mechanism of NADPH being used as the final cofactor in the biosynthesis of oxytetracycline.
Oxytetracycline can be used to correct breathing disorders in livestock. It is administered in a powder or through an intramuscular injection. American livestock producers apply oxytetracycline to livestock feed to prevent diseases and infections in cattle and poultry. The antibiotic is partially absorbed in the gastrointestinal tract of the animal and the remaining is deposited in manure. Researchers at the Agricultural Research Service studied the breakdown of oxytetracycline in manure depending on various environmental conditions. They found the breakdown slowed with increased saturation of the manure and concluded this was a result of decreased oxygen levels. This research helps producers understand the effects of oxytetracycline in animal feed on the environment, bacteria, and antimicrobial resistance.
Oxytetracycline is used to mark fish which are released and later recaptured. The oxytetracycline interferes with bone deposition, leaving a visible mark on growing bones.
Oxytetracycline has been formulated as a broad-spectrum anti-infective for fish under the name Terramycin 200 (TM200). It is used to control certain diseases that adversely affect salmonids, catfish, and .
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