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<p>The overall purpose of this project is to determine the effects of treatment of dairy calves with enrofloxacin on the emergence and endurance of antimicrobial resistant E. coli and Salmonella, and on the potential disruption of the normal healthy microbiota. Our goals for this project are to prospectively monitor the effect of treating calves with enrofloxacin at approved label dosages on the selection and spread of E. coli and Salmonella resistance to fluoroquinolones, identify fluoroquinolone resistance genes, and evaluate the disruption of the healthy fecal microbiota. Our objectives include: (1) longitudinally isolate and characterize E. coli (which will also be quantified) and Salmonella resistant to fluoroquinolone drugs and other common antimicrobials used in both human and veterinary medicine after treatment of calves with enrofloxacin or, as a control, tulathromycin, an antimicrobial of the macrolide class, and thus different in its mechanism of action from fluoroquinolones; (2) identify resistance genes in fecal E. coli and Salmonella, targeting genes that have been associated with development and persistence of resistance to fluoroquinolone drugs; (3) longitudinally characterize the disruption of the healthy fecal microbiota caused by the use of enrofloxacin or tulathromycin, evaluating the effects on the microbiota composition, which may affect host health and productivity. This project will provide quantitative knowledge necessary for science-based assessments of undesired effects from the use of enrofloxacin as a measure to control respiratory disease in calves. Additionally it will generate information to assist in management decisions aimed at reducing the dissemination of resistance to fluoroquinolones, supporting a sustainable animal production system benefiting both animal and public health. </p>
<p>NON-TECHNICAL SUMMARY: The use of antimicrobial drugs in food animals, specifically drugs in classes used also in human medicine remains a contentious public health issue. Quinolones are an antibiotic class regarded as critically important to human health. In 2008 the first quinolone drug was approved for the use in non-lactating dairy cattle, namely enrofloxacin. No study has evaluated the effect of the use of this drug in cattle on the selection of resistance to quinolones used in veterinary or human medicine. Additionally, studies with enrofloxacin in humans have shown that the use of this drug can disturb the gut microbiota, what in cattle could affect animal health and production. This project will provide use microbiological and genomic quantitative methods to allow science-based assessments of undesired effects from the use of enrofloxacin as a measure to control respiratory disease in calves. Additionally it will generate information to assist in management decisions aimed at reducing the dissemination of resistance to quinolones, supporting a sustainable animal production system benefiting both animal and public health. </p>