Tetracyclines are a group of antibiotics originally found in Streptomyces bacteria. Tetracyclines can be used against respiratory-tract infections, syphilis, and acne. Among the tetracyclines, there are chlortetracycline, doxycycline, oxytetracycline, and the original tetracycline.
Tetracycline use should be avoided during pregnancy and in the very young (less than 6 years) because it will result in permanent staining of teeth causing an unsightly cosmetic result.