Evaluation of a microbiological indicator test for antibiotic detection in ewe and goat milk

Abstract

Antibiotics are widely used for therapeutic and prophylactic purposes in dairy animals. The presence of residual antibiotics in milk could cause potentially serious problems in human health and have technological implication in the manufacturing of dairy products. The aim of this study was to evaluate Delvotest Accelerator (DSM Food Specialties, Delft, the Netherlands), a new system for a fully automated microbial test to detect antibiotic residues in ewe and goat milk. Forty-three samples of raw, whole, refrigerated bulk-tank milk samples (22 of ewe milk and 21 of goat milk) were analyzed during the whole lactation period. Four concentrations of 4 antibiotics were diluted in milk: penicillin G at 1, 2, 3, and 4 μg/L; sulfadiazine at 25, 50, 100, and 200 μg/L; tetracycline at 50, 100, 200, and 400 μg/L; and gentamicin at 25, 50, 100, and 200 μg/L. The detection limit of the Delvotest Accelerator was calculated as the range of antibiotic concentrations within which 95% of positive result lie. The range of detection limit of penicillin G and sulfadiazine was easily detected by Delvotest Accelerator at or below the European Union maximum residue limits, both for ewe and goat milk samples. In contrast, the system showed a lower ability to detect tetracycline and gentamicin both for ewe and goat milk samples. Very low percentages of false-positive outcomes were obtained. Lactation phase did not seem to be a crucial factor affecting the ability of the Delvotest Accelerator to detect spiked milk samples. A higher detection ability was observed for goat milk samples compared with ewe milk samples. A negative correlation between the percentage of positive milk samples detected and milk fat, protein, and lactose contents was observed for gentamicin only.

Evaluation of the rapid assay Betastar Combo 3.0 for the detection of Penicillin, Amoxicillin, Cefazolin and Oxytetracycline in individual sheep milk

“…This concern has conversely been highlighted in different other rapid on-farm tests on cow milk (Kneebone et al, 2010) but also in microbiological tests based on inhibition of microbial growth. In some papers dealing with sheep milk, different percentages of doubtful (0.6% in the paper by Montero et al, 2005;1% in Althaus et al, 2009) and falsepositive results (0.18% in Comunian et al, 2010) have been reported during the procedures for examination of antibiotics-free samples. False-positive results have been also recorded using a different version of Betastar Combo on individual ewe milk samples: 0.8% by Beltrán et al (2013) and 1.2% for the sole tetracyclines line by Beltrán et al (2014).…”

“…Many screening tests have been proposed and utilized to detect antibiotics in milk. Some of the methods which are available on the market are based on inhibition of microbiological growth and these have also been evaluated on ewe milk (Montero et al, 2005;Comunian et al, 2010). Other tests, based on chromatographic methods and denominated rapid screen tests are able to provide a faster result on milk (Kantiani et al, 2009) and milk products (Kneebone et al, 2010).…”

“…The test provides a result in 3 min and is based on the reaction of binding reagents linked to gold particles (Neogen, 2011). The particular composition of sheep milk could significantly influence the detection of antibiotics in this matrix (Comunian et al (2010), and for this reason the different versions of Betastar ® Combo have been tested and used both on cow (Reybroeck et al, 2010) and sheep milk (Beltrán et al, 2014).…”

Milk hygiene in small ruminants: A review

“…calidolactis. Different studies on the sensitivity of microbial tests have been developed in the last two decades by different authors using sheep and goat milk (Contreras et al, 1997;Molina et al, 2003;Sierra et al, 2009a,b;Comunian et al, 2010;Beltrán et al, 2013) and important efforts have been carried out in recent years by manufacturers to improve the performance and sensitivity of microbial tests (IDF, 2010). As a whole, microbial inhibitor tests using Geobacillus stearotermophilus var.…”

Evaluation of false positive results in microbial inhibitor tests for screening antibiotics in goat milk

“…It is important to mention that our results are obtained for milk samples from individual animals, which present a higher variability on composition and quality parameters, while in control quality programmes in general bulk milk samples are analysed, which present a lower percentage of positivet results (Comunian et al, 2010).…”