Anti-Dicloxacillin polyclonal antibody

An automated reversed-phase high-performance liquid chromatography (HPLC) method with UV detection at 300 nm alter on-line coupled solid-phase extraction (SPE) and photochemical post-column derivatization was developed for the residue analysis of or;acillin, cloxacillin and dicloxacillin in raw milk. After a centrifugal-ion step for defatting and ultrafiltration, a HPLC-integrated SPE using a restricted access sorbent, is performed. By operating the system in parallel mode, SPE and HPLC run are performed simultaneously. The procedure allows the analysis of about 30 samples within 24 h and was used to investigate the milk of cows which had been treated with oxacillin. The detection limit was 3 mu g/kg for oxacillin and cloxacillin and 5 mu g/ kg for dicloxacillin. The recoveries were between 66% and 81% with coefficients of variation between 3.3% and 7,7%. Using an acetonitrile extraction procedure better recoveries of greater than or equal to 90% were obtained with fortified samples, but more or less identical results were obtained for the samples with incurred residues after correction for recovery.

The aim of the present study was to evaluate an agar medium for the quantitative analysis of bifidobacteria in probiotic milk products on the market, and to investigate the identities of active strains. For this purpose, three sour milk products and a soft cheese brand were each analysed ten times with Wilkins-Chalgren agar (WCA) supplemented with mupirocin, and with MRS agar supplemented with dicloxacillin at two different concentrations. By statistical analysis of the bacterial counts obtained, WCA was shown to have the best detection rate. All the sour milk products examined conformed to Swiss food legislation and contained more than 10(6) cfu of bifidobacteria per gram of living bifidobacteria. All the samples of soft cheese analysed revealed counts that were clearly (approximately 2 logs) below this minimum requirement. Isolated bifidobacteria strains were all identical with reference strains from producer companies shown by pulsed-field gel electrophoresis (PFGE) profiling. According to the labels, the three brands of sour milk examined contained different strains of bifidobacteria (Bifidobacterium lactis Bb 12, Bifidobacterium animalis DN 173010 and Bifidobacterium species 420). However, all the strains revealed repeatedly identical PFGE-patterns, thus showing a close relationship. These findings show that a better taxonomical definition of commercially used bifidobacteria strains is needed.