Quality control guidelines for disk diffusion and broth microdilution antimicrobial susceptibility tests with seven drugs for veterinary applications

This multicenter study proposes antimicrobial susceptibility (MIC and dish diffusion methods) quality control (QC) parameters for seven compounds util ized in veterinary health. Alexomycin, apramycin, tiamulin, tilmicosin, and tylosin were tested by broth microdilution against various National Commit tee for Clinical Laboratory Standards (NCCLS)-recommended QC organisms (Sta phylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212, Streptococ cus pneumoniae ATCC 49619, Escherichia coli ATCC 25922, and Pseudomonas aer uginosa ATCC 27853). In addition, disk diffusion zone diameter QC limits we re determined for apramycin, enrofloxacin, and premafloxacin by using E. co li ATCC 25922, P. aeruginosa ATCC 27853, and S. aureus ATCC 25923. The resu lts from five or six participating laboratories produced greater than or eq ual to 99.0% of MICs and greater than or equal to 95.0% of the zone diamete rs,within suggested guidelines. The NCCLS Subcommittee for Veterinary Antim icrobial Susceptibility Testing has recently approved these ranges for publ ication in the next M31 document.