Antimicrobial agent detection in ewes' milk by the microbial inhibitor test brilliant black reduction test-BRT AiM®

The detection limits of 24 antimicrobial agents were determined in ewes' milk by one commercially available version of brilliant black reduction test, BRT Inhibitor Test with prediffusion AiM(R) (BRT AiM(R)). For each drug, eight concentrations were tested on 20 milk samples from individual ewes. The detection limits of the BRT AIM(R) method were determined by means of logistic regression models: 6 mug kg(-1) amoxycillin, 6 mug kg(-1) ampicillin, 51 mug kg(-1) cloxacillin, 2 mug kg(-1) penicillin "G", 230 mug kg(-1) cefadroxil. 1330 mug kg(-1) cephalosporin "C"; 270 mug kg(-1) cephalexin, 92 mug kg(-1) cefoperazone, 120 mug kg(-1) ceftiofur, 69 mug kg(-1) cefuroxime, 6000 mug kg(-1) streptomycin, 1200 mug kg(-1) gentamycin, 3700 mug kg(-1) neomycin, 630 mug kg(-1) erythromycin, 120 mug kg(-1) tylosin, 390 mug kg(-1) doxycycline, 5500 mug kg(-1) oxytetracycline, 6200 mug kg(-1) tetracycline, 5400 mug kg(-1) sulfadiazine, 3200 mug kg(-1) sulfamethoxazole. 6500 mug kg(-1) sulfamethoxypyridazine, 6200 mug kg(-1) sulfaquinoxaline, 22000 mug kg(-1) chloramphenicol and 4100 mug kg(-1) trimethoprim. The BRT AiM(R) method presents detection limits for beta-lactam antibiotics that are similar to those obtained as Maximum Residue Limits (MRLs) according to Regulation 2377/90 EEC as set out by the European Union. However, for other antimicrobial agents the estimated limits were higher than those of the EU-MRLs. It is therefore advisable to enhance the sensitivity of the method for the detection of the different antimicrobial groups or to develop a combined system of different microbiological inhibitor tests that would enable the detection of a greater number of antimicrobial agents. (C) 2003 Elsevier Ltd. All rights reserved.