AbstractsBiology & Animal Science

Analytical strategy for the detection of antibiotic residues in milk from small ruminants

by Martínez Mª Beltrán

Institution: TDX
Year: 2016
Keywords: Antibiotics; Screening tests; Sheep milk; Goat milk; PRODUCCION ANIMAL
Posted: 02/05/2017
Record ID: 2065395
Full text PDF: http://hdl.handle.net/10251/48164


In Mediterranean countries, sheep and goat’s milk production has traditionally been destined for the manufacture of cheese, often as raw milk. Cheese quality is closely related to milk composition but also to hygienic aspects such as somatic cell count, bacteriology or presence of antibiotic residues, currently regulated by European legislation. The implications of the presence of antibiotic residues in milk as a result of veterinary treatments include negative effects on consumer’s health such as allergies or antibiotic resistance and problems on the manufacturing processes of fermented products. For the screening of milk samples for antimicrobial residues, there are various methods available, microbial inhibitor tests and assays based on specific receptors, both widely used, especially in farms, the dairy industry and control laboratories. Screening methods have been validated for the use in raw milk from cows, but information on the performance of these tests in sheep and goat’s milk is rather limited. The aim of this study was to evaluate the performance of some microbial and receptor-binding screening tests to detect antibiotics in sheep and goat’s milk according to Commission Decision 2002/657/EC to determine their suitability to monitor the presence of antibiotic residues in milk and establish the most convenient analytical strategy in Spain. The Detection capability (CCβ) of microbial screening tests, the BRT MRL, the Delvotest MCS SP-NT, the Delvotest MCS Accelerator and the Eclipse 100, was at or below the maximum residue limits (MRLs) for most beta-lactam antibiotics assessed and other non-beta-lactam drugs such as neomycin, tylosin, sulfadiazine and sulfadimethoxine. However, they were less sensitive in the detection of quinolones and tetracyclines at safety levels. When individual milk samples were analysed, microbiological tests showed a higher occurrence of non-compliant results in sheep milk than in goat’s milk, being related in all cases to an elevated somatic cell count (SCC). The microbiological system consisting of two complemetary microtiter plates containing Geobacillus stereathermophilus var. calidolactis and Bacillus subtilis, respectively, allows improving the detection level in sheep milk with respect to the use of a single commercial test using G. stearothermophilus, detecting some quinolone and macrolide substances more closely related to their respective MRLs. The rapid receptor-binding assays (the Betastar Combo, the Charm MRL BLTET, the SNAP Betalactam, the SNAP Tetracycline and the TwinsensorBT) were able to detect most beta-lactams and tetracyclines at or below MRLs (CCβ ≤ MRL). A higher specificity of the rapid receptor tests was obtained in all cases even when individual milk samples were analysed. Only the TwinsensorBT test presented non-compliant results when antibiotic-free milk samples from individual animals were analysed, especially in the last weeks of lactation. No cross-reactions were found when drugs belonging to antimicrobial groups other than beta-lactams or…