|Harrison, Mark - UNIVERSITY OF GEORGIA|
Submitted to: Southern Poultry Science Society Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: October 21, 2006
Publication Date: January 22, 2007
Citation: Ladely, S.R., Harrison, M.A., Cray, P.J., Berrang, M.E., Englen, M.D., Meinersmann, R.J. 2007. Development of Macrolide Resistanct Campylobacter in Broilers Administered Subtherapeutic or Therapeutic Levels of Tylosin. Southern Poultry Science Society Meeting Abstracts. 43 T129. Technical Abstract: The use of antimicrobials in food animal production, particularly those commonly used to treat infections in humans, has become a source of controversy in recent years. However, limited data are available regarding the development of resistance from subtherapeutic or therapeutic administration of antimicrobials in animal production. The objective of this study was to evaluate the effect of FDA approved levels of tylosin administration on susceptibility of C. jejuni and C. coli isolated from ceca of treated broilers. In each of three replicate studies, day-of-hatch chicks were exposed to C. jejuni or C. coli. At two weeks of age, tylosin was administered at subtherapeutic (22 ppm, continuously in the diet) or therapeutic levels (529 ppm in drinking water for 5 days). Each week 5 broilers were sacrificed, total and resistant Campylobacter were enumerated from individual ceca plus contents. Macrolide resistance was observed at a higher frequency (P<0.01) among C. coli isolates 70.8% (17 /24) compared to C. jejuni isolates 36.8% (35/95). Resistance was observed at a significantly higher frequency (P<0.001) when tylosin was administered at subtherapeutic levels (62.7 %, 47/75), compared to administration of therapeutic levels (11.4 %, 5/44). Subtherapeutic administration resulted in recovery of 83.3 % (15/18) and 56.1 % (32/57) macrolide resistant isolates compared to only 33.3 % (2/6) and 7.9 % (3/38) of the isolates expressing macrolide resistance following administration of therapeutic levels, for C. coli and C. jejuni, respectively. Further studies are needed to determine the factors involved in the apparent difference in the acquisition of macrolide resistance in C. coli compared to C. jejuni.