Studies of the virulence and plasmid properties of Yersinia enterocolitica revealed a plasmid, 42.2 ± 1.1 megadaltons in size, which is associated with the pathogenicity and calcium dependency of this organism.
Alternatives to antibiotics are urgently needed in animal agriculture. The form these alternatives should take presents a complex problem due to the various uses of antibiotics in animal agriculture, including disease treatment, disease prevention, and growth promotion, and to the relative contribution of these uses to the antibiotic resistance problem. Numerous antibiotic alternatives, such as pre- and probiotics, have been proposed but show variable success. This is because a fundamental understanding of how antibiotics improve feed efficiency is lacking, and because an individual alternative is unlikely to embody all of the performance-enhancing functions of antibiotics. High-throughput technologies need to be applied to better understand the problem, and informed combinations of alternatives, including vaccines, need to be considered.
The spread of antibiotic-resistant pathogens requires new treatments. As the rate of development of new antibiotics has severely declined, alternatives to antibiotics must be considered in both animal agriculture and human medicine. Products for disease prevention are different from those for disease treatment, and examples of both are discussed here. For example, modulating the gut microbial community, either through feed additives or fecal transplantation, could be a promising way to prevent certain diseases; for disease treatment, non-antibiotic approaches include phage therapy, phage lysins, bacteriocins, and predatory bacteria. Interestingly, several of these methods augment antibiotic efficacy by improving bacterial killing and decreasing antibiotic resistance selection. Because bacteria can ultimately evolve resistance to almost any therapeutic agent, it is important to continue to use both antibiotics and their alternatives judiciously.
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