An official website of the United States government.
Unfortunately, the use of antibiotics for the promotion of growth of livestock requires the long-term subtherapeutic addition of the antibiotic in the feed. This type of feeding has been shown to increase the prevalence of antibiotic-resistant bacteria in the animal. This increase in antibiotic-resistant bacteria and their genetic determinants in the animal may result in an increase in antibiotic-resistant bacteria in the food supply, which could ultimately result in human illnesses. The use of specific naturally occurring compounds may provide strategies for controlling or decreasing the prevalence of antimicrobial resistant bacteria in domestic animals. These naturally occurring compounds include many plant bioflavinoids and oligosaccharides. <p> We will utilize a systematic approach to evaluate the effect that diet supplementation may have on the relative proportion of antibiotic resistant bacteria in the gut.
Non-Technical Summary:<br/>
Worldwide, there is a trend to limit AGP use in food animals to protect food safety and public health; however, this limit poses challenges for the animal feed and feed additive industries. The lack of information about microbial function, diversity and dynamics in the animal intestine in response to AGP treatment has hampered development of effective alternative strategies to improve animal production without use of AGPs.
<P>
Approach:<br/>
We propose that natural plant flavinoids will cure bacteria carrying antibiotic-resistant plasmids. Analysis: An in vitro model that examines the effects of specific compounds on the growth of antimicrobial resistant bacteria will be based on the growth rate studies described by Watanabe et al. (1971). Isolates demonstrating multiple plasmid mediated antibiotic resistance will be grown in the presence of naturally occurring plant phenolic to determine the minimum inhibitory concentration of each isolate to that compound. Isolates will be evaluated following phenolic exposure to determine variations in the antibiotic susceptibility patterns or zone size. Curing experiments as described by Lakshni et al. (1989) will be performed, once the presence of plasmid-mediated resistance has been confirmed. These studies will evaluate the effectiveness of several natural phenolic compounds found in plants to induce the loss of antibiotic resistant plasmids from antimicrobial resistant bacteria. Minimum inhibitory concentrations for the test compound will be determined for each isolate. A minimum of three sub-inhibitory concentrations of each compound will be utilized to study the curing. Approximately 300 colonies after each treatment will be evaluated for resistance or sensitivity by replica plating. A plasmid screen as described previously will confirm the percentage of curing. The percent curing activity of the test compounds will be compared to the percent curing of known curing agents like ethidium bromide and iododeoxy-uridine. Determine the effectiveness of the phenolic compounds in antibiotic resistant foodborne pathogens. Compounds that are effective in the general enteric population will also be effective in the predominate food borne pathogens. These isolates would include Campylobacter spp., Yersinia spp., Salmonella spp., E.coli and E.coli O157: H7. Evaluate the potential of phenolic feed supplementation and management practices to reduce the colonization and prevalence of antimicrobial resistant bacteria in pigs. Analysis: In vitro studies will be performed in batch culture and artificial intestinal systems.