Tetracyclines (TCs) are members of a group of broad-spectrum
antibiotics, the polyketides, particularly effective against many
gram-positive, gram-negative bacteria and protozoan parasites.1
There are 3 main classes of TCs: class 1 (chlortetracycline
(CTC), oxytetracycline (OTC), tetracycline (TET) and demethylchlortetracycline, class 2 (demeclocycline and methacycline) and
class 3 (doxycycline (DOXY), glycylcyclines and minocycline
(MINO). While TCs belonging to class 1 are used in agriculture
(fish, bovine, porcine and poultry), class 2 and 3 are mainly used
for diseases treatment in pets. Each year, the worldwide production of TCs is estimated to be in thousands of tons. For instance,
the amount used in the European Union for therapeutic purpose
end of last century was around 2294 tons, whereas during the period 2000-2001 the consumption in USA increased from 3000 to
3200 tons. Moreover, TCs are considered as one of the cheapest
classes of antibiotics available and are employed in the prophylaxis and therapy of human and animal infections particularly in
developing countries with limited health care budgets, especially
in animal production, as growth promoters, where costs are always a concern