In vitro susceptibility testing and quality control parameters for sarafloxacin (A-56620): a fluoroquinolone used for treatment and control of colibacillosis in poultry. Quality Control Study Group.

Sarafloxacin (formerly A-56620) is a fluoroquinolone recently introduced into veterinary practice for the therapy of colibacillosis and other indicated infections. Sarafloxacin was noted to be very active and comparable to ciprofloxacin and enrofloxacin for inhibiting 823 strains from a wide variety of species at < or = 1 or < or = 2 micrograms/mL. In vitro susceptibility tests for sarafloxacin using National Committee for Clinical Laboratory Standards (NCCLS) methods were also studied and interpretive criteria for Escherichia coli-associated colibacillosis isolates were proposed: susceptible at < or = 0.06 microgram/mL (> or = 25 mm) and resistant at > or = 0.25 microgram/mL (< or = 21 mm). Sarafloxacin agar dilution MIC results were approximately one log2 dilution higher than broth microdilution endpoints. The interpretive criteria demonstrated a low error rate of 5.9%, with a very major rate of only 0.5% (correlation coefficient between methods = 0.94). Quality control trials in six laboratories established MIC and zone diameter (5-microgram disk) limits for the NCCLS recommended strains: for the broth microdilution test, E. coli ATCC 25922 = 0.008 to 0.03 microgram/mL, Pseudomonas aeruginosa ATCC 27853 = 0.12 to 1 microgram/mL, Enterococcus faecalis ATCC 29212 = 0.5 to 2 micrograms/mL, and Staphylococcus aureus ATCC 29213 = 0.06 to 0.25 microgram/mL; and for the disk diffusion test, E. coli ATCC 25922 = 30 to 36 mm, S. aureus ATCC 25923 = 25 to 30 mm, and P. aeruginosa ATCC 27853 = 23 to 29 mm. These criteria for in vitro tests with sarafloxacin should enable the longitudinal monitoring of its activity against the indicated pathogens and allow detection of emerging resistant populations that may necessitate altered dosing regimens.