Effects of antibiotic regimens on resistance of Escherichia coli and Salmonella serovar Typhimurium in swine
Alan G. Mathew, MS, PhD; Felix Jackson, MS; Arnold M. Saxton, MS, PhD
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Objective: To determine the effects of antibiotic dosing schemes on resistance patterns of naturally occurring Escherichia coli and a challenge strain of Salmonella serovar Typhimurium in swine.
Methods: In two trials, 96 weaned pigs were inoculated with Salmonella Typhimurium prior to being treated with antibiotics. Treatments included maximum label use, rotation of similar and non-similar antibiotics, increasing gradient doses, and pulse dosing, for a period of 2 weeks post challenge. Fecal samples were obtained before, during, and after antibiotic treatment for isolation of the challenge organism and E coli for resistance analysis using a minimum inhibitory concentration analysis.
Results: The E coli from pigs treated with pulse doses of antibiotics had lower resistance compared to other groups. Greater resistance occurred in E coli when similar antibiotics were used in rotation. Resistance of Salmonella Typhimurium was not affected by treatment and remained low throughout the study.
Implications: Antibiotic regimens appear to affect antibiotic resistance in bacteria associated with swine. Thus, dosing schemes that will simultaneously decrease risks posed by antibiotic resistance elements should be considered when formulating effective therapeutic or subtherapeutic antibiotic treatments. Such practices should address consumer concerns regarding agricultural use of antibiotics and increase acceptance of pork products.
Keywords: antibiotic resistance, Escherichia coli, Salmonella Typhimurium
Cite as: Mathew AG, Jackson F, Saxton AM. Effects of antibiotic regimens on resistance of Escherichia coli and Salmonella serovar Typhimurium in swine. J Swine Health Prod 2002;10(1):7-13.
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