Validação de métodos imunoenzimáticos para determinação de resíduos de antimicrobianos no leite

Abstract

In order to evaluate the efficiency of Charm MRL BL/TET, SNAP beta-lactams and SNAP tetracyclins kits for detecting antimicrobials residues in milk, raw milk samples without antimicrobials were inoculated with 21 drugs in four different concentrations considering the Brazilian legal limit (MRL) and the detected level of the kits. The 21 antimicrobials from six different groups and positive and negative controls were tested with 30 repetitions/level. During all the experiment, the blocks temperature was measured and the milk quality was evaluated for total bacterial count, somatic cell count, determination of fat, protein, lactose, total and solids non fat content. The experiment was carried out from June to September, 2009. The temperatures varied from 44 to 47 ºC in Kits SNAPs blocks and from 55 to 57 ºC to Charm MRL BL/TET kit and were considered satisfactory. The titrable acidity of the milk samples varied from 14.35 to 16.56 ºD. Considering all the limit level of antimicrobial detection (N3) defined by the kits manufacturer, discrepancies were not observed. All the kits detected the different antimicrobials in level 2 that correspond to MRL concentration (Brazilian legislation) and also some detect in level 1 (N1) that is the half of the N3 concentration. The Snap Tetracyclin kit detection of tetracyclin, oxitetracyclin and clortetracyclin in N2 level varied from 90 to 100%. For beta-lactams, the sensitivity in N2 level varied from 93.3 to 100% and ceftiofur (N1) was detected in 76.7 %. Beta-lactams such as cefazolina were detected in 100%; sodium dicloxacylin in 90.0% and cloxacillin in 66.7% by Snap beta-lactams kit. In Charm MRL Beta/TET kit, the detection for level 2 (N2) was 100% for the majority of the antimicrobials, exception for cloxacilin (93.3%). Ceftiofur was detected in 100% of all the milk samples tested. In relation to N3 level, the Charm MRL Beta/TET kit detected cefalexin in 23.3% and cefapirin in 20.0%; cefazolin was not detected. The Snap Beta-lactams kit did not detect tetracyclins and the Snap Tetracyclin kit did not detected beta-lactams. Although statistical difference (P > 0.05) was not noted when the results were evaluated visually compared with the kits reader, some results were not similar. It can be concluded that all the tested kits are efficient for detecting antimicrobials in milk and they can be used as screening tests for monitoring these substances in milk. The kits reader must be obligatory for screening antimicrobial residues in milk.