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An LC method for the determination of the aminoglycosides streptomycin (STR) and dihydrostreptomycin (DHS) in milk was developed/modified on the basis of published papers. Mean recoveries were 87 and 95% for STR and DHS, respectively. Recoveries are dependent on the concentration level and batch of solid-phase extraction columns used, and independent of fat content and homogenization. The relative standard deviations are 15.6 and 9.6% for STR and DHS, respectively, at a level of 100 micrograms kg-1. Limits of detection (8 and 12 micrograms kg-1, respectively) and quantification (12 and 18 micrograms kg-1, respectively) are far below the EU maximum residue limit of 200 micrograms kg-1. Lyophilized DHS samples can be used for internal control of the analysis as the DHS concentration is not influenced by the lyophilization process and subsequent storage at 6 degrees C. In incurred milk samples no false negative results of preliminary confirmation tests (Charm II Aminoglycoside test, Ridascreen Streptomycin ELISA) with respect to DHS concentrations > or = 20 micrograms kg-1 as determined by the LC method are observed. DHS concentrations of incurred samples determined by ELISA are higher than those obtained by the LC method. These differences were more pronounced with incurred than with spiked milk samples, thus leading to the conclusion that in incurred samples substances are present which co-react in the ELISA and which are not detected by the LC method.

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-In this study enumeration of bacterial cells in raw sheep's bulk milk by an automated flow cytometry method (Bactoscan FC) was evaluated. The results were discussed with respect to the results obtained by the analysis of cow's milk. Within-laboratory reproducibility, which depended on the counting level, was slightly worse than that of raw cow's milk (valued in the interval > 50 Individual Bacterial Cell (IBC)·µL -1 ). In routine procedure, if preceding samples had counts > 20 000 IBC·µL -1 , then this was observed to increase the count of the following sample significantly in many cases ("carry-over"). Bactoscan counts were moderately enhanced with increasing numbers of somatic cells in sheep's milk. However, this trend was indicated only in samples with lower plate counts (< 10 5 colony-forming units (CFU)·mL -1 ). The regression equation between the results of the anchor plate method and the Bactoscan method was computed from the sample set which represented sheep's milk production in Slovakia during 2004 (data between percentiles 1 and 99, n = 877): log 10 CFU·mL -1 = 1.088 log 10 IBC·µL -1 + 2.292; with an accuracy of the estimate, expressed as standard deviation of regression s y,x = 0.305 log 10 CFU·mL -1 . The actual regression for raw cow's milk was verified, introducing both raw cow's milk samples and raw sheep's milk samples. The transformation of IBC·µL -1 to CFU·mL -1 realised by various published conversions was evaluated by testing of the parallelism of the regression lines and also by comparison of obtained differences on a model data set. The conclusions support the requirement to set up a special conversion for the intended field of application at any time. Résumé -L'application de la cytométrie de flux pour déterminer la qualité bactériologique du lait cru de brebis en Slovaquie. Dans cette étude, la numération des cellules bactériennes a été évaluée dans le lait cru de brebis de grand mélange par la cytométrie de flux automatisée (Bactoscan FC). Les résultats ont été comparés à ceux obtenus sur le lait de vache. La reproductibilité interne au laboratoire augmentait avec le niveau de la numération et était légèrement inférieure à celle obtenue sur lait cru de vache (pour les valeurs > 50 cellules bactériennes individuelles (CBI)·µL -1 ). La méthode de routine a montré que si les échantillons précédents avaient un niveau de contamination > 20 000 CBI·µL -1 , cela pouvait fréquemment augmenter significativement les valeurs dénombrées dans l'échantillon suivant ("carry over"). L'augmentation des cellules somatiques dans le lait de brebis entraînait une légère augmentation des valeurs de dénombrements par Bactoscan. Cependant cette tendance n'a été observée que dans les échantillons ayant les plus faibles niveaux de dénom-brements sur boîte (< 10 5 unités formant des colonies (UFC)·mL -1 ). L'équation de régression entre les résultats de dénombrements sur boîte et de dénombrements par Bactoscan a été calculée à partir de l'ensemble des échantillons représentant la production du lait de b...

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