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Minimum inhibitory concentration breakpoints and disk diffusion inhibitory zone interpretive criteria for tilmicosin
T R Shryock1, D W White, J M Staples
1Animal Science Discovery and Development, Elanco Animal Health, Division of Eli Lilly and Co., Greenfield, IN 46140, USA.
Abstract:
Tilmicosin is a novel macrolide antibiotic developed for exclusive use in veterinary medicine. The first tilmicosin-containing product was approved to treat bovine respiratory disease associated with pasteurellae. The development of antimicrobial susceptibility testing guidelines for tilmicosin was predicated on the relationship of clinical efficacy studies that demonstrated a favorable therapeutic outcome, on pharmaco-kinetic data, and on in vitro test data, as recommended by the National Committee for Clinical Laboratory Standards (NCCLS). The NCCLS-approved breakpoints for the MIC dilution testing are resistant > or = 32 micrograms/ml, intermediate 16 micrograms/ml, and susceptible < or = 8 micrograms/ml. The zone of inhibition interpretive criteria for disk diffusion testing with a 15-micrograms disk are resistant < or = 10 mm, intermediate 11-13 mm, and susceptible > or = 14 mm.
Insights
Tilmicosin, a veterinary antibiotic, has established guidelines for antimicrobial susceptibility testing. These guidelines, based on clinical data, pharmacokinetic studies, and in vitro testing, ensure effective treatment of bacterial infections in animals.
Area of Science:
- Veterinary Pharmacology
- Antimicrobial Resistance
- Clinical Microbiology
Background:
- Tilmicosin is a novel macrolide antibiotic exclusively for veterinary use.
- The initial tilmicosin product targeted bovine respiratory disease caused by pasteurellae.
Purpose of the Study:
- To establish antimicrobial susceptibility testing guidelines for tilmicosin.
- To define breakpoints for MIC dilution and disk diffusion testing.
Main Methods:
- Guidelines were developed based on clinical efficacy, pharmacokinetic data, and in vitro test results.
- Recommendations followed the National Committee for Clinical Laboratory Standards (NCCLS) guidelines.
- MIC dilution and disk diffusion testing methods were utilized.
Main Results:
- NCCLS-approved MIC breakpoints: resistant ≥ 32 µg/ml, intermediate 16 µg/ml, susceptible ≤ 8 µg/ml.
- Disk diffusion criteria (15 µg disk): resistant ≤ 10 mm, intermediate 11-13 mm, susceptible ≥ 14 mm.
Conclusions:
- Standardized testing guidelines and breakpoints are crucial for the effective use of tilmicosin in veterinary medicine.
- These guidelines facilitate accurate diagnosis and appropriate treatment of bacterial infections in animals.