Detection limits of antimicrobial agents in ewe milk by Delvotest

In the present work the different detection limits of 24 anti-infectious agents were determined in ewe milk. For each drug, 8 concentrations were assayed on 20 ewe milk samples coming from ewe individual. detection limitsof the Delvotest® method were: 5 μg/kg amoxicillin, 3 pg/kg ampicillin, 23 μg/kg cloxacillin, 1.4 μg/kg penicillin"G", 63 μg/kg cefadroxil, 610 μg/kg cephalosporin "C"; 68 pg/kg cephalexin, 41 μg/kg cefoperazone, 59 μg/kg Ceftiofur®, 41 μg/kg cefuroxime, 10000 pg/kg streptomycin, 1200 μg/kg gentamicin, 3300 pg/kg neomycin, 980 μg/kg erythromycin, 120 μg/kg tylosin, 450 μg/kg tetracycline, 420 μg/kg oxytetracycline, 290 μg/kg doxycycline, 260 μg/kg sulfadiazine, 110 μg/kg sulfamethoxazole, 430 μg/kg sulfametoxypyridazine, 190 μg/kg sulfaquinoxaline, 23000 μg/kg chloramphenicol and 860 μg/kg trimethoprim. The sensitivity to those sulphonamides and p-lactam antibiotics whose MRLs have been established by European Union were 100% (amoxicillin, ampicillin, cloxacillin, Ceffiofur®, penicillin "G", sulfamethoxazole), 73.3% (sulfadiazine) and 43.3% (sulfamethoxypyridazine). The low sensitivity of B. stearothermophilus var. calidolactis in detecting the residues of aminoclycosides, macrolides, tetracyclines, chloramphenicol and trimethoprim residues in ewe milk indicates the need to improve the method conditions for these groups or develop an integrated residue detection system for ewe milk with different sensitive microorganisms for each group of anti-infectious agents.