Navrátilová P., Borkovcová I., Vyhnálková J., Vorlová L. (2011): Fluoroquinolone residues in raw cow's milk. Czech J. Food Sci., 29: 641-646.The aim of the study was to monitore the levels of fluoroquinolone residues in bulk samples of raw cow's milk. The bulk samples of raw cow's milk (n = 150) were obtained from 58 different milk suppliers in the South Moravian and Vysočina Regions. The samples were analysed by reverse phase high-performance liquid chromatography method with fluorescence detection and gradient elution. 87.3% of the raw milk samples were positive for the fluoroquinolones residues. Flumequine was present in none of the samples. The levels of other fluoroquinolones investigated were below the recommended maximum residue limit. The results of the study indicate that fluoroquinolones are frequently administered to the dairy cows in spite of the recommendations of CVMP. The most frequently determined was enrofloxacin and its indicator residue, i.e. ciprofloxacin. An efficient control of the veterinary drugs residues in milk is very important to ensure the safety of the milk and milk products.

IntroductionPlate diffusion methods play an important role in the monitoring system for antimicrobial agents in raw materials and foodstuffs of animal origin. The aim of this work was to select a Yersinia spp. strain for the plate diffusion method based on sensitivity to a fluoroquinolone, namely flumequine. Another aim was to determine the optimal conditions of the method with the selected strain of Yersinia ruckeri CCM 8467 and to determine the detection capability (CCβ) of this method for residues of selected fluoroquinolones in milk.Material and MethodsOptimum method conditions were set: cell concentration in the test agar at the level of 9.105–106 CFU/mL, discs with a diameter of 12.7 mm, Antimicrobial Inhibitor Test Agar with a pH of 6.0, and incubation at 30°C for at least 18 h and up to 24 h.ResultsWith respect to the maximum residue limit (MRL), the Y. ruckeri plate method demonstrated the lowest sensitivity to flumequine. The CCβ of the method for flumequine was in the concentration of 100 μg/L-1 (twice the MRL). The study also confirmed that the method exhibits very good sensitivity to the other tested fluoroquinolones, which were marbofloxacin (30 μg/L, 0.4 MRL), ciprofloxacin (10 μg/L, 0.1 MRL), and enrofloxacin (20 μg/L, 0.2 MRL), but lower sensitivity to danofloxacin (42 μg/L, 1.4 MRL).ConclusionThe method with the CCM 8467 strain of Y. ruckeri showed a higher sensitivity to flumequine than the method with the ATCC 11303 strain of E. coli.

Navrátilová P., Vyhnálková J., Vorlová L., Jeřábková J. (2014): A plate diffusion method for detecting fluoroquinolone residues in raw cow's milk. Czech J. Food Sci., 32: 260-264.The plate diffusion method is a reference method in the Czech Republic for determination of residues of antimicrobial agents in raw materials and foodstuffs of animal origin. A new method using the E. coli strain ATCC 11303 for the detection of fluoroquinolones was introduced in 2008. The aim of this study was to determine the detection capability (CCβ) of this modified method using this E. coli strain for selected fluoroquinolones registered in the Czech Republic for treating diseases in cattle -danofloxacin, marbofloxacin, ciprofloxacin, enrofloxacin, and flumequine. When comparing the maximum residue limits for individual fluoroquinolones and the CCβ values determined, we can state that the method displays very good sensitivity to ciprofloxacin and enrofloxacin (20 and 40 µg/l), marbofloxacin (70 µg/l), and danofloxacin (30 µg/l). The CCβ of the method for flumequine was not found in concentrations ≤ MRL. The method did not display sensitivity to flumequine even in a concentration equal to twelve times the MRL.

The aim of this study was to determine the detection capability (CCβ) of a multi-plate diffusion method for selected cephalosporins for which the maximum residue limits (MRLs) in milk have been set (ceftiofur, cefoperazone, cephalexine, cephazoline, cephalonium, cephapirine, cefquinome). The multiplate method was composed of Bacillus subtilis BGA CCM 4062 plates (agar pH of 6, 8 and 7.2); Kocuria rhizophila CCM 552 plate, Geobacillus stearothermophilus CCM 5965 plate and Escherichia coli CCM 7372 plate. Geobacillus stearothermophilus plate showed the highest sensitivity. CCβ for the tested cephalosporins was determined at MRLs or lower, except for cefquinome, which was undetectable even at 12 × the MRL. Kocuria rhizophila plate showed the highest sensitivity to ceftiofur (CCβ = 100 μg/l); cephazoline and cephalonium could not be detected even at 12 × times the MRL. Escherichia coli plate was most sensitive to cefoperazone (CCβ = 60 μg/l). Other than cephapirine, none of the cephalosporins could be detected by B. subtilis BGA (pH 6, 8 and 7.2) plates even at 12 × the MRL. Our results demonstrate the differences in sensitivity to selected cephalosporins of the individual plate methods that together form the multi-plate method. The multi-plate method is sensitive enough to detect most of the tested cephalosporins, with the exception of cefquinome, which could not be detected at levels close to MRL.