Display options
Share it on

Front Microbiol. 2012 Apr 10;3:139. doi: 10.3389/fmicb.2012.00139. eCollection 2012.

Excretion of antibiotic resistance genes by dairy calves fed milk replacers with varying doses of antibiotics.

Frontiers in microbiology

Callie H Thames, Amy Pruden, Robert E James, Partha P Ray, Katharine F Knowlton

Affiliations

  1. Department of Dairy Science, Virginia Tech Blacksburg, VA, USA.

PMID: 22514550 PMCID: PMC3322659 DOI: 10.3389/fmicb.2012.00139

Abstract

Elevated levels of antibiotic resistance genes (ARGs) in soil and water have been linked to livestock farms and in some cases feed antibiotics may select for antibiotic resistant gut microbiota. The purpose of this study was to examine the establishment of ARGs in the feces of calves receiving milk replacer containing no antibiotics versus subtherapeutic or therapeutic doses of tetracycline and neomycin. The effect of antibiotics on calf health was also of interest. Twenty-eight male and female dairy calves were assigned to one of the three antibiotic treatment groups at birth and fecal samples were collected at weeks 6, 7 (prior to weaning), and 12 (5 weeks after weaning). ARGs corresponding to the tetracycline (tetC, tetG, tetO, tetW, and tetX), macrolide (ermB, ermF), and sulfonamide (sul1, sul2) classes of antibiotics along with the class I integron gene, intI1, were monitored by quantitative polymerase chain reaction as potential indicators of direct selection, co-selection, or horizontal gene transfer of ARGs. Surprisingly, there was no significant effect of antibiotic treatment on the absolute abundance (gene copies per gram wet manure) of any of the ARGs except ermF, which was lower in the antibiotic-treated calf manure, presumably because a significant portion of host bacterial cells carrying ermF were not resistant to tetracycline or neomycin. However, relative abundance (gene copies normalized to 16S rRNA genes) of tetO was higher in calves fed the highest dose of antibiotic than in the other treatments. All genes, except tetC and intI1, were detectable in feces from 6 weeks onward, and tetW and tetG significantly increased (P < 0.10), even in control calves. Overall, the results provide new insight into the colonization of calf gut flora with ARGs in the early weeks. Although feed antibiotics exerted little effect on the ARGs monitored in this study, the fact that they also provided no health benefit suggests that the greater than conventional nutritional intake applied in this study overrides previously reported health benefits of antibiotics. The results suggest potential benefit of broader management strategies, and that cost and risk may be avoided by minimizing incorporation of antibiotics in milk replacer.

Keywords: antibiotic resistance genes; dairy calves; manure; milk replacer

References

  1. J Appl Microbiol. 2011 Aug;111(2):511-23 - PubMed
  2. Prev Vet Med. 2004 Jan 30;62(1):59-72 - PubMed
  3. Antimicrob Agents Chemother. 2001 May;45(5):1374-8 - PubMed
  4. Microb Drug Resist. 2001 Summer;7(2):183-90 - PubMed
  5. Appl Environ Microbiol. 2001 Jan;67(1):22-32 - PubMed
  6. Environ Sci Technol. 2010 Aug 15;44(16):6102-9 - PubMed
  7. Vet Res. 2005 Sep-Dec;36(5-6):723-34 - PubMed
  8. Environ Microbiol. 2007 Mar;9(3):819-23 - PubMed
  9. J Antimicrob Chemother. 2003 Aug;52(2):159-61 - PubMed
  10. J Dairy Sci. 2003 Dec;86(12):3963-6 - PubMed
  11. Vet Microbiol. 2009 May 12;136(3-4):397-402 - PubMed
  12. J Biol Chem. 2004 Dec 10;279(50):52346-52 - PubMed
  13. J Clin Microbiol. 2000 Jul;38(7):2774-7 - PubMed
  14. Appl Environ Microbiol. 2009 Nov;75(22):7125-34 - PubMed
  15. Clin Microbiol Rev. 2011 Oct;24(4):718-33 - PubMed
  16. J Clin Microbiol. 2008 Jun;46(6):1968-77 - PubMed
  17. FEMS Microbiol Lett. 2008 Jan;278(2):207-12 - PubMed
  18. Appl Environ Microbiol. 2007 Jul;73(14):4407-16 - PubMed
  19. J Antimicrob Chemother. 2003 Oct;52(4):623-8 - PubMed
  20. Nutr J. 2010 May 22;9:23 - PubMed
  21. Drug Resist Updat. 1998;1(2):109-19 - PubMed
  22. Prev Vet Med. 1997 Jul;31(1-2):95-112 - PubMed
  23. Antimicrob Agents Chemother. 2002 Feb;46(2):525-7 - PubMed
  24. Vet Microbiol. 2010 Sep 28;145(1-2):76-83 - PubMed
  25. Appl Environ Microbiol. 2006 Jun;72(6):4214-24 - PubMed
  26. Appl Environ Microbiol. 2002 Apr;68(4):1786-93 - PubMed
  27. J Anim Sci. 2009 Oct;87(10):3418-26 - PubMed
  28. J Anim Sci. 1994 Mar;72(3):683-9 - PubMed
  29. Appl Environ Microbiol. 2004 Dec;70(12):7372-7 - PubMed
  30. J Hosp Infect. 1997 Oct;37(2):89-101 - PubMed
  31. Microb Ecol. 2008 Feb;55(2):184-93 - PubMed
  32. J Environ Qual. 2007 Oct 16;36(6):1695-703 - PubMed
  33. Mol Cell Probes. 2001 Aug;15(4):209-15 - PubMed
  34. Appl Environ Microbiol. 2000 Nov;66(11):4605-14 - PubMed
  35. J Dairy Sci. 2010 Feb;93(2):574-81 - PubMed
  36. Appl Environ Microbiol. 2006 Jun;72(6):3872-8 - PubMed
  37. Prev Vet Med. 2006 Jul 17;75(1-2):123-32 - PubMed
  38. Water Res. 2006 Jul;40(12):2427-35 - PubMed
  39. Nat Rev Microbiol. 2006 Aug;4(8):608-20 - PubMed
  40. Appl Environ Microbiol. 2007 Jan;73(1):156-63 - PubMed
  41. Am J Vet Res. 2006 Sep;67(9):1580-8 - PubMed
  42. J Am Vet Med Assoc. 2010 Jun 15;236(12):1338-44 - PubMed
  43. J Clin Microbiol. 2001 Nov;39(11):4193-5 - PubMed
  44. Microb Drug Resist. 2004 Fall;10(3):231-8 - PubMed
  45. Appl Environ Microbiol. 2001 Apr;67(4):1494-502 - PubMed
  46. Science. 2009 Aug 28;325(5944):1128-1131 - PubMed
  47. J Dairy Sci. 2009 Jan;92(1):286-95 - PubMed
  48. J Dairy Sci. 2011 Sep;94(9):4556-65 - PubMed
  49. Pharmacoepidemiol Drug Saf. 2004 May;13(5):323-31 - PubMed
  50. J Dairy Sci. 2009 Sep;92(9):4707-14 - PubMed
  51. J Med Microbiol. 2010 Jun;59(Pt 6):702-707 - PubMed
  52. J Appl Microbiol. 2009 Apr;106(4):1336-42 - PubMed

Publication Types