International Journal of Microbiology and Allied Sciences, Feb 2015, Volume 1 Issue 3 International Journal of Microbiology and Allied Sciences (IJOMAS) ISSN: 2382-5537 February 2015, 1(3):42-48 ©IJOMAS, 2015 An introduction to tetracycline antibiotics: applications and resistance Tahir Hussain 1 , Farida Nighat 2 , Muhsin Jamal 1 , Saadia Andleeb 1 1 Atta-ur-Rahman School of applied Biosciences (ASAB) National University of Sciences and Technology (NUST), Islamabad, Pakistan 2 Islamic International Medical College, Riphah International University, Rawalpindi, Pakistan Corresponding Author: Tahir Hussain Atta-ur-Rahman School of applied Biosciences (ASAB) National University of Sciences and Technology (NUST), Islamabad, Pakistan Email: pak_biotechnologist@yahoo.com Abstract Key words: Applications, generations, resistance, tetracycline. Introduction Discovered as natural products from actinomycetes soil bacteria, the tetracyclines were first reported in the scientific literature in 1948 [1]. Tetracycline antibiotics were effective against a wide range of microorganisms including gram- positive and gram-negative bacteria, chlamydiae, mycoplasmas, rickettsiae, and mycoplasma and protozoan parasites [2], and have been widely used against a variety of infections in human, animals [3], and plants [3][4], and have also been used as growth promoters in animal agriculture and aquaculture [5]. Research show that tetracycline antibiotics are second most extensively used antimicrobials worldwide [6]. Tetracyclines are one of the cheapest antibiotics, hence extensively used in countries with limited health care budgets [7]. Soon after the discovery of tetracycline, resistance was reported in Shigella dysenteriae [8]. Since then a wide range of tetracycline resistant bacterial strains have been identified [9]. Tetracycline resistance in bacteria is by one of these three main mechanisms: active efflux, ribosomal protection proteins (RPPs), or enzyme- mediated drug inactivation [10]. Resistance to tetracycline antibiotics has been reported in a range of bacterial species inhabiting variety of animals, and diverse environmental conditions. This review focuses and gives an introduction to the generation of tetracycline antibiotics, bacterial resistance mechanisms, and tetracycline resistance bacteria reported from diverse sources. Generations of tetracycline The tetracycline antibiotics which were in use or prepared between (1948-1963) referred to as first- generation including chlorotetracycline, tetracycline, oxytetracycline, second-generation tetracyclines are the ones which were introduced between (1965 to 1972), and include doxycycline Mini Review Article Page: 42-48 Tetracyclines are one of the oldest broad spectrum and cheapest antibiotics used for treating variety of infections in humans and as growth promoters in animals. The extensive applications of tetracycline have produced resistance in a range of bacterial species inhabiting variety of animals, and diverse environmental conditions. 42