ANTIBIOTICS, from ἀντί = against, and βίος = life. - The term antibiosis was used for the first time, in 1889, by P. Vuillemin, to designate certain manifestations of vital competition among microorganisms. It was more recently taken up again by S. A. Waksman, E. S. Horning, M. Welsch and H. B. Woodruff (1942) to designate the action of a category of chemical substances produced by microbial metabolism, capable of inhibiting the multiplication or the metabolic activities of other microorganisms. This definition, however, proves increasingly incomplete and inexact, the more our knowledge of antibiosis expands, and the more its boundaries extend, to the point of becoming confused with those of other phenomena of microbicidy and vital competition.
In any case, by a. are meant substances produced by the metabolism of living beings, mostly lower plants, but also higher plants and even animals (M. Pavan). Their chemical constitution, which is perfectly known to us only for some, is extremely complex and varied, and does not allow us a definition or a delimitation by this route. In their action, which manifests itself even at very strong dilutions, antibiotics display a certain specificity, more or less strict.
The first observations on antibiosis go back to the very father of bacteriology, to Pasteur, who already from 1877 had noted the antagonistic action exerted by certain saprophytic germs on the anthrax bacillus, and had drawn from it hopes of therapeutic applications. Many other scholars in the following decades observed phenomena of antibiosis, and some even attempted some therapeutic application, which however had little following.
The antibiotic era in medicine was inaugurated only recently, with the discovery of penicillin, identified and studied in 1929 by A. Fleming, subsequently purified and tested by H. W. Florey, Chain, and a whole numerous series of scholars. Penicillin, produced by a mould: Penicillium notatum, is particularly active in infections from cocci and in those from spirochetes, and its introduction into therapy has brought about a true revolution in the prognoses and the course of these diseases, making it possible at times to cut short in a few hours extremely grave morbid pictures and rendering favorable prognoses that were previously absolutely fatal.
A second a. that is acquiring a very notable importance in medicine is streptomycin, produced by Streptomyces griseus, discovered and studied by Waksman and collaborators. This a. acts especially on those germs that do not benefit from penicillin therapy. Particularly important is its therapeutic action in tuberculosis, which, although not yet completely clarified and defined in its limits and its possibilities, has nonetheless aroused great enthusiasms and hopes.
Numerous antibiotics have been isolated and studied, but as regards their applications in therapy, they are still in an experimental phase. Among these the best known are: gramicidin, tyrothricin, subtilin, chloromycetin, polymyxin, etc.
Apart from the very high practical importance that antibiotics have in medicine, they are also of interest from a purely theoretical point of view. Some have wished to give a finalistic interpretation of them, considering them as a means of defense of living beings against other living beings, in the struggle for life. It cannot be excluded that, at least in some cases, this may correspond to the truth, but one must not generalize either. Even within the same species of microorganisms, only a few strains are capable of producing antibiotics in notable measure, and only under very particular environmental conditions, such as are exceptionally encountered in nature. Moreover, antibiotic activity is exerted with particular intensity against germs that very rarely are in vital competition with the microorganism producing the a. Furthermore, germs, as can be ascertained experimentally, succeed with relative ease in adapting to the a.: that is, they become antibiotic-resistant.
Therefore, even if one may admit that antibiosis may constitute one of the many weapons that living beings bring into play in vital competition, one cannot on the other hand attribute to it a purely finalistic value, and one must recognize that the phenomenon of antibiosis is one of the many admirable phenomena of harmony-disharmony encountered in the unfathomable mystery of life.
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