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U.S. Department of Health and Human Services

Animal & Veterinary

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Use of Resistance Thresholds to Manage Risk

SLIDE 1: Using the Resistance Threshold to Manage Risk

Linda Tollefson, DVM, MPH
FDA Center for Veterinary Medicine

January 24, 2001


SLIDE 2: Resistance Threshold

  • Maximum allowable prevalence of resistant bacteria on animal-derived food that does not pose an unacceptable impact on human health
  • Established for a particular antimicrobial used in animals and correlated to the human health impact threshold
  • If the Resistance Threshold is exceeded, the drug is no longer shown to be safe in a given food animal species


SLIDE 3: Resistance Threshold

  • Trigger for initiating immediate withdrawal from the label of the species that has reached the resistance threshold
  • Measured by NARMS -- slaughter plant isolates or retail food isolates
  • If decreases in susceptibility or changes in the prevalence of resistance among animal isolates are observed but the resistance threshold is not exceeded, mitigating actions may be implemented.


SLIDE 4: Resistance Threshold

  • Predetermined and transparent; the “bright line”
  • Goal is to ensure that significant human antimicrobial therapies are not lost due to use of antimicrobials in food animals
  • Allows all interested parties to observe changes in resistance levels, for individual drugs or relative to other drugs used in the same species


SLIDE 5: Resistance Threshold

  • Allows for self-regulation
    • Mitigating actions would be voluntary
    • Reinforce Judicious Use Guidelines
  • Provides guidance to seek additional approvals
  • Direct research on antimicrobial resistance by highlighting where more information is needed


SLIDE 6: AVMA Judicious Use Activities

  • Steering Committee on Judicious Use
    • completed general guidelines
    • species specific guidelines
  • Swine, cattle and poultry guidelines developed
  • Contracted with CVM to develop material about judicious use, including
    • booklets
    • videotape script
    • speeches


SLIDE 7: Judicious Use of Antimicrobials

  • Maximizes therapeutic effect while minimizing development of resistance
    • only for proven clinical infections
    • Appropriate dose and duration of treatment
    • Certain antibiotics held in reserve
  • Monitor success of prudent use by comparing resistance levels to established thresholds
    Select drugs for a particular disease etiology based on current resistance levels relative to a threshold ? VADS


SLIDE 8: CVM Home Page