Proposed quality control guidelines for antimicrobial susceptibility tests using tilmicosin

Area of Science:

• Veterinary Microbiology
• Antimicrobial Susceptibility Testing
• Pharmacology

Background:

• Tilmicosin is a macrolide antibiotic exclusively for veterinary use.
• Standardized quality control (QC) is essential for reliable antimicrobial susceptibility testing (AST).
• Established National Committee for Clinical Laboratory Standards (NCCLS) procedures are crucial for method validation.

Purpose of the Study:

• To develop and validate quality control guidelines for tilmicosin.
• To establish proposed QC ranges for disk diffusion and broth microdilution methods.
• To ensure accurate and reproducible tilmicosin susceptibility testing in veterinary settings.

Main Methods:

• Multi-laboratory study adhering to NCCLS M23-T2 guidelines.
• Tilmicosin incorporated into Sensititre plates for broth microdilution.
• Tilmicosin incorporated into 15-microgram disks for Kirby-Bauer disk diffusion.
• Testing utilized cation-adjusted Mueller-Hinton broth and sheep blood-supplemented agar.
• Reference bacterial strains: Pasteurella haemolytica, Pasteurella multocida, and Staphylococcus aureus.

Main Results:

• Replicate tests were conducted across multiple laboratories and media lots.
• Data generated from broth microdilution and disk diffusion testing.
• Proposed quality control ranges were determined for both AST methods.

Conclusions:

• Validated quality control guidelines for tilmicosin susceptibility testing have been developed.
• The proposed QC ranges will aid in ensuring the accuracy of veterinary diagnostic testing.
• Standardized QC procedures are critical for the reliable use of tilmicosin in animal health.