Detection limits of four antimicrobial residue screening tests for β-lactams in goat's milk

Abstract

This study was conducted to compare the detection limits (DL) of several antibiotic residue screening tests with the maximum residue limits (MRL) authorized by the EU according to the guidance for the standardized evaluation of microbial inhibitor tests of the International Dairy Federation. Composite antibiotic-free milk samples from 30 primiparous Murciano-Granadina goats in good health condition were used to prepare test samples spiked with different concentrations of each antimicrobial. In total, 5,760 analytical determinations of 10 beta-lactam antibiotics (penicillin-G, ampicillin, amoxicillin, cloxacillin, oxacillin, dicloxacillin, cefadroxyl, cefalexin, cefoperazone, and cefuroxime) were performed using 4 antibiotic residue screening tests: the brilliant black reduction test BRT AiM (AiM-Analytik in Milch Produktions-und Vertriebs GmbH, München, Germany), Delvotest MCS (DSM Food Specialties, Delft, the Netherlands), Eclipse 100 (ZEU-Inmunotec SL, Zaragoza, Spain), and the Copan Milk Test (CMT; Copan Italia SpA, Brescia, Italy). For each method, we estimated the detection limits of the antimicrobial agents using a logistic regression model. Using the CMT and Delvotest on samples spiked with the 8 antibiotics for which MRL were available, DL were at or below the MRL. The BRT test provided DL at or below the MRL for all of the agents except cefalexin, whereas the Eclipse 100 method failed to detect 4 antibiotics (ampicillin, amoxicillin, cloxacillin, and cefoperazone) at MRL or below. Logistic regression-determined levels of agreement were highest for the CMT method (98.6 to 100%) and lowest for Eclipse 100 (66.3 to 100%). In general, agreement levels indicated good correlation between observed results and those predicted by logistic regression. The lowest b values (closely related to test sensitivity) were recorded for the cephalosporins (0.074 to 0.430) and highest for penicillin G, ampicillin, and amoxicillin (11.270 to 11.504). Delvotest and CMT best fulfilled IDF criteria for the ideal test for detecting antibiotic residues in milk.

Performance of current microbial tests for screening antibiotics in sheep and goat milk

“…calidolactis being highly sensitive to these substances. Several studies on the microbial test sensitivity using sheep milk have been carried out in the last two decades (Althaus, Torres, Montero, Balasch, & Molina, 2003a;Molina, Althaus, Molina, & Fern andez, 2003), while very few studies have been undertaken in goat milk (Sierra et al, 2009a(Sierra et al, , 2009b, demonstrating that these tests are able to detect b-lactams at or below the maximum residue limits (MRLs) established by European legislation (EC, 2010), but cannot suitably detect other veterinary drugs. Therefore, modifications such as the addition of chelating agents into the culture medium to enhance the detection of tetracyclines, respectively, of antifolates to improve sulphonamide detection have been proposed (Langeveld, Beukers, Bommele, & Stark, 2005), and consequently manufacturers have improved some performance characteristics of microbial screening tests in new versions now available.…”

Selective Advantage of Resistant Strains at Trace Levels of Antibiotics: a Simple and Ultrasensitive Color Test for Detection of Antibiotics and Genotoxic Agents

“…The sensitivities of the test vary with the antibiotic being assayed. In milk, sensitivities range from 2 to 57 ng/g (or ml) for ␤-lactams, 434 to 1,140 ng/g for tetracyclines, 66 to 353 ng/g for sulfonamides, 23 to 2,482 ng/g for macrolides, 200 to 6,180 ng/g for aminoglycosides, and 2,730 to 3,750 ng/g for the fluoroquinolones ciprofloxacin and enrofloxacin (29,41,42). The detection levels in a similar test are considerably lower in animal food products following extraction by chemical methods (45).…”

Interference of non-specific detergents in microbial inhibitor test results for screening antibiotics in goat's milk

“…The DLs for penicillins (Table 2) were below those of the MRLs established by legislation (Commission Regulation (EU) No 37/2010) and also lower than the DLs calculated by Sierra et al (2009) in goat's milk. This suggests the greater sensitivity of the current versions of these screening tests as a result of the improvements made by manufacturers in recent years.…”