Abstract
This article presents a microbiological system composed of a " BT" bioassay (Beta-lactams and Tetracyclines) and a " QS" bioassay (Quinolones and Sulfonamides). The " BT" bioassay contains spores of Geobacillus stearothermophilus, bromocresol purple and cloramphenicol in a culture medium (incubation time: 2.45h), while the " QS" bioassay uses spores of Bacillus subtilis, trifenyltetrazolium - toluidine blue and trimethoprim in a suitable culture medium (incubation time: 5.5h). The detection capability (CC ß) of 27 antimicrobial agents in ovine milk were determined by logistic regression models. Thus, the " BT" bioassay detects amoxycillin, ampicillin, penicillin " G" , cloxacillin, oxacillin, cephalexin, cefoperazone, ceftiofur, chlortetracycline, oxytetracycline, tetracycline, neomycin, gentamycin and tylosin, while " QS" bioassay detects: ciprofloxacin, enrofloxacin, marbofloxacin, sulfadiazine, sulfadimethoxine, sulfamerazine, sulfamethazine, sulfamethoxazole, sulfathiazole, erythromycin, lincomycin and spiramycin at levels close to their respective Maximum Residue Limits. The simultaneous use of both bioassays detects a large number of antibiotics in milk given each method's adequate complementary sensitivity. © 2011 Elsevier B.V..
