Antibiotics are produced either synthetically or by a process of fermentation from natural products of bacteria, algae, or fungi. They are used to kill microorganisms or slow down or stall their growth. We distinguish between antibiotics which target only very few microorganisms or bacteria (narrow spectrum) and those which act against wide range of microorganisms or bacteria (broad spectrum). Repeated intake of antibiotics and declining susceptibility may lead to individual microorganisms developing antibiotic resistance. This diminishes the antibiotic’s medical therapeutic effect; it may also become entirely ineffective. Furthermore, only non-resistant bacteria will be destroyed or limited in number. This can be a reason for a significant imbalance in the gut flora.
Antibiotics systematically attack one or several of the bacteria’s molecules or proteins. As early as the end of 19th century, antibiotic effects had been discovered. Only once penicillin – from the fungus Penicillium – had been researched and further developed did in the 1940s the industrial production of penicillin begin internationally, and later of other antibiotics. Some 7,000 different antibiotics have been discovered or developed so far, yet only very few of these are suitable for medical or veterinary uses.