Veterinary use and antibiotic resistance

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Veterinary use and antibiotic resistance

• 635.313
• Genetisch modifizierte Organismen in der Umwelt
• Svjetlana Medjakovic

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Antibiotics in Veterinary use

• more than 1 million tons released into biosphere
  in the last 50 years
• globally estimated 50 for veterinary and
  agricultural purposes

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Antibiotics in Veterinary use

• veterinary use of antibiotics includes the use
  on
• pets
• farm animals
• animals raised in aquaculture
• for farm animals, antibiotics are used
• in therapy and prophylaxis
• to increase growth and feed efficiencies ? at
  subtherapeutical levels!

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Antibiotics in Veterinary use

• bacteria that develop antibiotic resistance in
  animals comprise
• food-borne pathogens
• opportunistic pathogens
• commensal bacteria
• the danger same antibiotic resistance genes and
  gene transfer mechanisms can be found in the
  microfloras of animals and humans
• the accumulation of resistant bacteria and the
  spread via agriculture and direct contamination
  by the use of antibiotics in agriculture and
  veterinary medicine are documented

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Antibiotics in Veterinary use

• EU Switzerland in 1999 13.216 t antibiotics
• according to data of FEDESA (European Federation
  of Animal Health) the amount of antibiotics which
  were used to increase growth and feed
  efficiencies was twice as high as 1997

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Antibiotics in Veterinary use

• in Austria at present there are 4 antibiotics
  permitted in animal feed (not for products of the
  AMA-cachet)
• Monensin-Sodium
• Sylinomycin-Sodium
• Avilamycin
• Flavophospholipol
• according to a board decision of the EU they will
  be forbidden from january 2006

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Antibiotic Resistance

• existed even before antibiotics were used by
  humans
• but this intrinsic form of resistance is not a
  major source of concern for human and animal
  health? majority of drug-resistant organisms have
  instead emerged as a result of genetic changes

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Antibiotic Resistance

• Acquired Resistance
• mutational resistance ? result of spontaneous
  mutation in a locus on the microbial chromosome
  that controls susceptibility to a given
  antibiotic
• transferable resistance ? plasmids, transposons
  and integrons, can code for multi-resistance

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Antibiotic Resistance

• Multiple Resistance
• microorganisms resistant to a certain antibiotic
  may also be resistant to other antibiotics that
  share a mechanism of action or attachment
• microorganisms may be resistant to several
  unrelated antibiotics. Use of one such
  anti-biotic will therefore also select for
  resistance to the other antibiotics!

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Antibiotic Resistance

• imprudent use of antibiotics leads to an
  increased selection pressure on bacteria
• molecular analysis of antibiotic resistance
  genes, plasmids and transposons has demonstrated
  that identical elements are found in animals and
  humans

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Epidemiology of Resistance

• selection for resistant bacterial population
  whenever an animal or human host is exposed to
  antibiotics
• selection depends upon
• type of antibiotic
• number of individuals treated
• dosage regimen
• duration of treatment

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Resistance Transfer

• multiple sources of resistant microorganisms
• animals and their faeces
• food of animal origin
• fruits or vegetables
• contaminated water
• humans

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Resistance Transfer via Farm Animals

• carry-over in milk and meat products
• contamination of vegetables with animal
  excrements
• direct contamination with food containing
  resistant bacteria, through the digestive system
  is discussed, but up to present not clearly proved

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Improvement of the Situation

• reduce the occurrence of antimicrobial resistance
  in the microflora of food animals by removing
  selective pressure
• study of Aarestrup et al. after banning
  Avoparcin in Denmark 1995, the prevalence of
  glycopepdtid-resistent fecal enterococci from
  food animals dropped from 72,7 to 5,8 in 2000!

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Thanks for your Attention!