The emergence of bacterial resistance to tetracyclines, a broad class of antibiotics, has led to a decline in their use against infectious diseases. Due to the development of resistance, tetracyclines are no longer used in the treatment of many conditions where they were the drugs of choice. Dozens of bacterial diseases were once treated with tetracyclines, and that number is now reduced to only a handful. In those instances where tetracyclines are still used, or even are currently the drugs of choice, the possibility still exists for rapid development of bacterial resistance to this class of antibiotics. This is an unfortunate turn of events, because tetracyclines are broad-range, inexpensive and safe antibiotics that show good oral absorption. Moreover, the development of tetracycline resistance in some instances may come along with the development of concurrent multiple-antibiotic resistance, and alternative antibiotics also may become ineffective in such cases. Therefore the need for new antimicrobial regimens addressing the problem of antibiotic resistance is acute.