P-043. The Use of Macrolide Antibiotics in Turkeys and Subsequent Effects on the Emergence of Macrolide Resistant Campylobacter Species

G. T. Danzeisen, J. S. Sherwood, J. L. Thorsness, J. E. Axtman, C. M. Logue;
North Dakota State Univ., Fargo, ND.

The aim of this study was to determine the effects of the therapeutic use of tylosin in turkeys on the emergence of macrolide resistant Campylobacter spp. One flock consisting of approximately 30,000 turkeys was followed for 18 weeks during the entire grow out period followed by sample collection at a processing facility. Random fecal samples were collected during weekly visits and Campylobacter spp. were isolated from the feces using direct plating and enrichment methods. Campylobacter spp. were first isolated when the poults were 3 weeks old. At 4 weeks the flock was split into two separate flocks of 15,000 birds and each flock was moved into separate finishing barns. One half was designated as the treated flock and the other was used as a control. The treated flock received therapeutic doses of tylosin after the birds were colonized with Campylobacter, during weeks 5, 12 and 16. Of the 1655 isolates obtained during sampling 412 were tested for resistance to erythromycin using the agar dilution method. Antibiotic concentrations ranged from 0.03 µg/ml to 256 µg/ml. No macrolide resistant Campylobacter spp. were detected prior to the first round of tylosin dosing. Approximately 50% of the isolates tested from the treated group were found to be resistant to erythromycin with MICs greater than 32 µg/ml; of these isolates 99% had MICs >256 µg/ml. When isolates from the control group were tested only 3% were found to be resistant with MICs >256 µg/ml. Macrolide resistant Campylobacter spp. were recovered from the cecal contents of turkeys at the processing facility which indicates that it is possible for these organisms to contaminate turkey carcasses. From this study it may be concluded that the therapeutic use of macrolides can select for resistance in a turkey production environment.