Evaluation of Screening Test for Detection of Antimicrobial Residues in Ewe Milk

Abstract

The effects of preservatives (potassium dichromate and sodium azide), heat treatment (untreated and 82 degrees C/10 min), and lactation stage upon the response of the microbial tests (BRT AiM and Delvotest) utilized for the detection of residues of antimicrobial substances in ewe milk were examined. Milk samples were collected from the morning milking of 50 Manchega ewes every 2 wk, from 15 d postpartum until the end of lactation. A total of 2322 samples were analyzed by BRT AiM with prediffusion and Delvotest microbial tests. The specificity of preservative-free milk samples without heat treatment was high (96.3% for BRT and 97.7% for Delvotest), with results improving for those samples thermally treated at 82 degrees C/10 min (99.0% for BRT and 98.7% for Delvotest). Potassium dichromate produced a total inhibition of growth of Bacillus stearothermophilus with both methods. When acidiol was utilized, the specificity of the samples not treated thermally was lower compared with preservative-free milk samples for the BRT AiM (90.2%) and Delvotest (91.0%) methods, improving when the samples were thermally treated, both for BRT AiM (94.8%) and Delvotest (95.3%), given that the presence of the preservative increased the frequency of doubtful results. The lactation stage significantly affected the results of the methods, with a greater frequency of false-positive and doubtful cases toward the end of the cycle, especially in those samples preserved with acidiol. The greater selectivity in both methods was therefore obtained for preservative-free ewe milk samples with prior heat treatment taken at the beginning or in midlactation period.

Survey of pyrethroid, macrocyclic lactone and antibacterial residues in bulk milk tank from Minas Gerais State, Brazil

“…These discrepancies could be due to the detection limits of the tests and the many analytes investigated by the confirmatory tests here (Molina et al 2003). In agreement with our data, Moats et al (1995) reported an inconsistency between Charm Tetracycline screening test results when compared with high-pressure liquid chromatography to detect oxytetracycline.…”

“…Furthermore, several authors have noted the problem of false-positive results in certain microbiological inhibitor tests. One possible cause for false-positive results in these screening tests is the presence of indigenous antimicrobial agents and free fatty acids (Moats et al 1995, Molina et al 2003, Le Breton et al 2007. Although these screening methods (i.e.…”

“…Although these screening methods (i.e. immunological or microbial inhibition assays) are widely used to detect the presence of veterinary drugs in foods, more accurate chromatographic methods coupled with highly specific and sensible detection systems, such as tandem mass spectrometry, are required to identify, confirm the presence of and quantify these compounds (Molina et al 2003, Samanidou & Nisyriou 2008, Toaldo et al 2012) because they provide full or complementary information enabling the unequivocal identification and quantification of the analyte at levels of interest (Samanidou & Nisyriou 2008).…”

Fatores fisiológicos, clínicos e farmacológicos, determinantes de resíduos de antimicrobiano no leite, avaliados em protocolos terapêuticos de mastite em bovinos leiteiros

“…A mastite é um dos problemas mais importantes nas propriedades leiteiras e a maior fonte de resíduos encontrados no leite (McEWEN et al, 1991, MOLINA et al, 2003a.…”

“…O fenômeno de múltipla-resistência tem assumido particular importância nas últimas décadas, tendo sido registrado em microrganismos isolados de humanos e de animais de produção, como verificado por vários autores estrangeiros e nacionais SCHILEGELOVA et al, 2002;CATRY et al, 2003;GARINO JR , 2004 A terapia antibacteriana em bovinos tem sido incriminada como um fator catalizador de resistência em bactérias isoladas de animais tratados, de outros animais na propriedade e de alimentos derivados destes animais (BERGHASH et al, 1983;GRIGGS et al1994;PIDDOCK., 1996), sendo a mastite, processo inflamatório da glândula mamária, a causa mais freqüente para o uso de antibacterianos em bovinos produtores de leite (McEWEN et al, 1991, COSTA et al, 2000aERSKINE et al, 2002, MOLINA et al, 2003.…”