Optimization of an antibiotic residue screening test, based on inhibition of Bacillus subtilis BGA, with experimental design.

ABSTRACT

Experimental design was applied to an agar-diffusion inhibition test for the screening of residues of veterinary antimicrobial drugs in slaughter animals. The effects and interactions of four independent parameters were studied the dextrose content of the culture medium, the trimethoprim concentration in the culture medium, the thickness of the agar-layer and the preincubation time. The effects on the inhibition zones of sulphadimidine, oxytetracycline, streptomycin and tylosin, substances of four different antibiotic groups were measured. An optimized multi-residue test was established with the parameter values that yielded the best sensitivity for the four substances.