Role of Probiotics and Prebiotics in Animal Feeding to Reduce Antibiotic Consumption

The development of antimicrobial resistance and the transference of antibiotic resistance genes from animal to human microbiota have emerged as a major problem in medicine. Indeed, pathogenic bacteria are proving to exhibit increasing degrees of Multi Drug Resistance (MDR), presumably in response to the common use of antibiotics. One of the principal cause of the widespread of MDR in bacteria has been scientifically strongly associated with the food chain. Indeed, for years farmers have applied low doses of antibiotics in animal feeding, since it was discovered that animals grew stronger and faster; on the other hand bacteria were developing genetic strategies to overcome this hurdle, expanding and spreading antibiotic resistance. In EU antibiotic growth promoters (AGP) have been recently banned because their use has been related to an increase in risks to human. Unfortunately, the plague has been diffused (each year in the EU alone, over 25000 people die from infections caused by MDR bacteria) and now the problem of MDR is considered a treat to mankind. One of the future researches, addressed to control and to prevent MDR, should focus on the gut microbiota activities to improve the understanding of the interactions with specific intestinal diseases, and on the mechanisms which allow the establishment of a proper equilibrium between different species in a microbial community. We should consider that in a microbial community, a stronger group is overtaking another for the competition of substrates. Consequently, we could induce and improve the growth of a given beneficial species in order to contrast pathogenic species. In particular, we could fight MDR and contrast pathogens with beneficial microbes and their growth promoters, as probiotics and prebiotics, respectively. Indeed, probiotic bacteria are known to reduce populations of many different entero-pathogens at cell surface both in vitro and in vivo. By means of ecological strategies, probiotics bacteria can overcome pathogens mainly by: competition, competitive exclusion and displacement, through known mechanisms such as the prevention of adhesion to binding sites, the production of bacteriocins and the variations of ecological factors (e.g. pH decrease). Moreover, the addition of selected prebiotics is recognized to enhance the probiotic community already resident in the gut and can strengthen its mucosal colonization to the disadvantage of pathogens and opportunistic microbes. Based even on our research experience made in vitro and in vivo, we have recently conducted works that are reflecting the suitability of probiotics to contrast pathogens, which will hence results in an alternative or a reduction for antibiotic use and misuse. For example, based on intestinal cell models we have demonstrated that selected Bifidobacterium species can reduce the adhesion of Campylobacter species, or that the supplementation in the feed of husbandry piglets of a symbiontic formula of probiotic and prebiotic can constitute for a prolonged period a protection from some pathogen bacteria. Moreover, the substitution of probiotics to AGP, resulted even in a gain weight and general better condition of the animals. Thus, both in vivo and in vitro the reduction of the number of cells of pathogens by probiotics competition is an assured fact by means of molecular analysis. Different research groups have demonstrated the ability of some probiotics species on limiting the growth of different Vancomycin-Resistant Enterococci (VRE). If we consider that the hallmark of antibiotic resistance in the food chain is the vancomycin resistance (VR), we can stress out the role of probiotics. For a long time vancomycin-like antibiotics were the most used AGP, and currently VR pathogens represent a new menace. These bacteria may remain on the carcasses of animals after slaughter and on foods and then contaminate human. In addition, since in human medicine vancomycin is considered a last line an...