Applications of bacteriocins in livestock.

Introduction Antibiotics have been used as therapeutic and prophylactic treatments to control a variety of bacterial infections in livestock for more than 50 years. Different types of antibiotics have also been fed at sub-therapeutic levels to cattle, poultry and swine to increase productivity and feed efficiency (McDermott et al., 2002). The emergence of antibiotic-resistance in many bacteria relevant for animal and public health stresses the importance of decreasing the use of antibiotics in animal production. The reduction of antibiotic application in livestock can only be achieved if alternative antimicrobial strategies are available. Among those interventions that have been investigated and applied are: immunization, diet modification, sanitation, feed additives, and probiotic bacteria (Callaway et al., 2004; Gillor et al., 2004). A variety of probiotic bacteria have been tested to control animal and foodborne pathogenic bacteria in livestock, but in many of them the beneficial effects have not been fully elucidated (Fuller, 1999). The mechanism of inhibition of pathogenic bacteria for several of those probiotic microorganisms is mediated by the production of bacteriocins. The application of bacteriocins such as colicins in livestock has been largely achieved by feeding bacteriocin-producing strains. Feeding purified bacteriocins to humans for control of diarrhea was reported in a few publications during the 1900’s (Papavassiliou, 1961), but there is very little evidence that administering bacteriocins alone to livestock has ever been done. The absence of that type of studies could be due to the likely rapid degradation of these proteinaceous compounds in the digestive tract of mammals. Because of this lack of evidence, our discussion on the use of bacteriocins in livestock will be largely based on those studies that reported feeding or applying bacteriocin-producing bacteria (BPB).