Identifying potential alternatives to antibiotics

Abstract Text: The greatest challenges to identifying antibiotic alternatives in animal agriculture are the numerous different uses of antibiotics:  disease treatment, disease prevention, and improved feed efficiency.  These various uses are achieved by administering antibiotics at either high or low concentrations, which beget different effects on both pathogenic and commensal gut bacteria.  Selecting an appropriate alternative is therefore dependent on the intended use of the antibiotic.  Three promising alternatives that address the different goals of antibiotic use will be discussed here:  phage therapy, vaccination, and modulation of gut bacteria (e.g. probiotics, prebiotics, synbiotics, or competitive exclusion).  Benefits and shortcomings of each of these strategies will be described.  Vaccination targets specific pathogens, which an advantage because few collateral effects will be experienced but is limited by knowledge of the etiological agent.  Phage therapy also benefits from being a targeted approach, but is akin to antibiotics because of the potential for resistance to develop when used imprudently.  Probiotic and similar modulators of the gut bacterial community are often reported as promising but lack experimental reproducibility, likely due to unknown principles governing the complex relationship between a host and its gut bacterial consortium.  The goal of research in our lab is to understand how growth-promoting antibiotics alter the intestinal bacterial community to enhance animal performance, and perhaps this information will inform efficacious antibiotic alternatives.  One avenue has been to define the effects of the growth-promoting antibiotic carbadox on the swine bacterial community.  Our results show that carbadox has an immediate (within seven days of initial administration) effect on the gut bacterial community, but that the community recovers even in the continued presence of carbadox.  Notably, the abundance of some bacteria (members of the Prevotella genus) remain constant during carbadox exposure while other bacterial populations temporarily decrease.  Further work is required to determine the potential of these bacteria as modulation targets.  As tightening regulations continue to limit antibiotic use, these and other alternatives to antibiotics merit continued exploration to improve animal health and food safety.

Keywords: antibiotics, antibiotic alternatives, carbadox, phage therapy, vaccines, probiotics