ANTIBIOTICS Historically, antibiotics are secondary metabolites produced by microorganisms that inhibit or kill a widespectrum of other microorganisms. Most of the useful ones are... ANTIBIOTICS Historically, antibiotics are secondary metabolites produced by microorganisms that inhibit or kill a widespectrum of other microorganisms. Most of the useful ones are produced by molds and bacteria of the genus Streptomyces, and a few by Bacillus and Paenibacillus spp. Many of the clinically useful agents now in use are synthetic products. Two antibiotics have been investigated extensively as heat adjuncts for canned foods: subtilin and tylosin. Chlortetracycline and oxytetracycline were once widely studied for their application to fresh foods, whereas natamycin is employed as a food fungistat. According to the Animal Health Institute, 22 million pounds of antibiotics were sold in the United States in 2002 for use in both farm and companion animals, a slight increase over 2001. Ninety percent of these agents were used to treat, control, and prevent diseases. In general, the use of chemical preservatives in foods is not popular among many consumers; the idea of employing antibiotics is even less popular. Some risks may be anticipated from the use of any food additive, but the risks should not outweigh the benefits overall. The general view in the United States is that the benefits to be gained by using antibiotics in foods do not outweigh the risks, some of which are known and some of which are presumed. Some 15 considerations on the use of antibiotics as food preservatives were noted by Ingram et al., and several of the key ones are summarized as follows: 1. The antibiotic agent should kill, not inhibit, the flora and should ideally decompose into innocuous products or be destroyed on cooking for products that require cooking. 2. The antibiotic should not be inactivated by food components or products of microbial metabolism. 3. The antibiotic should not readily stimulate the appearance of resistant strains. 4. The antibiotic should not be used in foods if used therapeutically or as an animal feed additive. The tetracyclines are used both clinically and as feed additives, and tylosin is used in animal feeds and only in the treatment of some poultry diseases. Neither nisin nor subtilin is used medically or in animal feeds, and although nisin is used in many countries, subtilin is not. The structural similarities of these two antibiotics may be noted. Read more