tetracycline, any of a group of antibiotics produced by bacteria of the genus Streptomyces. They are effective against a wide range of Gram positive and Gram negative bacteria, interfering with protein synthesis in these microorganisms (see Gram's stain). Tetracycline is used to treat rickettsial bacterial infections such as Rocky Mountain spotted fever, some eye, respiratory, intestinal, and urinary infections, some kinds of acne, and some diseases where the infecting microorganism is resistant to penicillin (see drug resistance). Tetracycline may cause permanent discoloration of developing teeth, and it is not given to pregnant and lactating women and growing children. Because of the development of strains of microorganisms resistant to the tetracyclines, these antibiotics have lost some of their usefulness. Aureomycin is a trade name for the derivative chlortetracycline, and Terramycin is a trade name for oxytetracycline.

Any of a class of broad-spectrum antibiotics with a common basic structure, including doxycycline. They may be isolated directly from several species of actinomycetes of the genus Streptomyces or modified from the compounds isolated. They are the drugs of choice in the treatment of cholera, rickettsial infections (see rickettsia), psittacosis, brucellosis, and tularemia; tetracyclines are also used in the treatment of acne. Overuse of these and other antibiotics has led to drug resistance in microorganisms.

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