Within a feasibility study the use of antibiotics in pigs and cattle was determined in 24 veterinary practices in Lower Saxony and on 66 farms in North Rhine-Westphalia in Germany. Focus was laid on the comparison of the Used Daily Doses (UDD) (dose per animal and day prescribed by the veterinarians) with the Defined Animal Daily Doses (ADD) (dose per animal and day calculated by means of recommended dosages and estimated live weights).

In human and mice, the ABC efflux transporter ABCG2 represents the main route for active drug transport into milk. In contrast, there is no detailed information on the role of ABCG2 in drug secretion and accumulation in milk of dairy animals. We therefore examined ABCG2-mediated drug transport in the bovine mammary gland by parallel pharmacokinetic studies in lactating Jersey cows and in vitro flux studies using the anthelmintic drug monepantel (MNP) as representative bovine ABCG2 (bABCG2) drug substrate. Animals received MNP (Zolvix®, Novartis Animal Health Inc.) once (2.5 mg/kg per os) and the concentrations of MNP and the active MNP metabolite MNPSO2 were assessed by HPLC. Compared to the parent drug MNP, we detected higher MNPSO2 plasma concentrations (expressed as AUC). Moreover, we observed MNPSO2 excretion into milk of dairy cows with high milk to plasma ratio of 6.75. In mechanistic flux assays, we determined a preferential time-dependent basolateral to apical (B>A) MNPSO2 transport across polarized MDCKII-bABCG2 monolayers using LC-MS/MS analysis. The B>A MNPSO2 transport was significantly inhibited by the ABCG2 inhibitor fumitremorgin C in bABCG2- but not in Mock-transduced MDCKII cells. Additionally, the antibiotic drug enrofloxacin, the benzimidazole anthelmintic oxfendazole and the macrocylic lactone anthelmintic moxidectin caused a reduction in the MNPSO2 (B>A) net efflux. Altogether, this study indicated that therapeutically relevant drugs like the anthelmintic MNP represent substrates of the bovine mammary ABCG2 transporter and may thereby be actively concentrated in dairy milk.

The molecular mechanisms by which environmental pollutants including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or widely used imidazole fungicide prochloraz display their toxic effects in vertebrates are still not well understood. Using computer analysis, we recently identified nuclear aryl hydrocarbon receptor (AhR) binding sites termed "dioxin response elements" (DREs) in the 5'-untranslated region (5'-UTR) of efflux transporter ABCG2 (Accession No. EU570105) from the bovine mammary gland. As these regulatory motifs mediate regulation of target genes by AhR agonists including TCDD and prochloraz, we have systematically investigated the effect of both contaminants on functional ABCG2 transport activity in primary bovine mammary epithelial cells. TCDD or prochloraz doubled ABCG2-mediated Hoechst H33342 secretion. This effect was almost completely reversed by specific ABCG2 inhibitor Ko143. In further mechanistic studies, we showed that this induction was due to binding of activated AhR to DRE sequences in the ABCG2 5'-UTR. Receptor binding was significantly reduced by specific AhR antagonist salicyl amide. Induction of AhR by TCDD and prochloraz resulted in a time- and dose-dependent increase of ABCG2 gene expression and transporter protein levels. As ABCG2 represents the main mammary transporter for xenobiotics including drugs and toxins, exposure to prevalent AhR agonists may enhance transporter-mediated secretion of potential harmful compounds into milk. Through identification of mammary ABCG2 as a novel target gene of pesticide prochloraz and dioxin, our results may therefore help to improve the protection of breast-feeding infants and the consumer of dairy products.

Healthy farm animals have been found to act as a reservoir of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (E. coli). Therefore, the objective of the study was to determine the input of antimicrobial active ceftiofur metabolites in the stable via faeces and urine after intramuscular administration of the drug to pigs and the elucidation of the Escherichia coli ESBL resistance pattern of treated and untreated pigs housed in the same barn during therapy. For determination of the minimal inhibitory concentration (MIC) the method of microdilutionaccording to the recommended procedure of the Clinical and Laboratory Standards Institute was used. Inaddition to that, a qualitative determination was performed by agar dilution. Unsusceptible E. coli speciesselected via agar dilution with cefotaxime were confirmed by MALDI-TOF and ESBL encoding genes wereidentified by PCR. The amounts of ceftiofur measured as desfuroylceftiofur (DFC) in the different probes (plasma, urine, faeces and dust) were analysed by UPLC-MS/MS. In a first experiment two groups of pigs (6 animals per group) were housed in the same barn in two separated boxes. One group (group B) were treated with ceftiofur according to the licence (3 mg/kg administered intramuscularly (i.m.) on three consecutive days, day 1–3). During a second treatment period (day 29–31) an increased rate of ESBL resistant E. coli was detectable in these treated pigs and in the air of the stable. Moreover, the second group of animals (group A) formerly untreated but housed for the whole period in the same stable as the treated animals revealed increased resistance rates during their first treatment (day 45–47) with ceftiofur. In order to investigate the environmental input of ceftiofur during therapy and to simulate oral uptake of ceftiofur residues from the air of the stable a second set of experiments were performed. Pigs (6 animals) were treated with an interval of 2 weeks for 3 days with different doses of ceftiofur (3 mg/kg, 1 mg/kg and 0.3 mg/kg i.m.) as well as with 3 mg/kg per os) and the renal and biliary excretion of ceftiofur as its active metabolite were measured in comparison to the plasma levels. In addition to that, probes of the sedimentation dust and the air of the stable were analysed for drug residues. The present study shows that treatment of several animals in a stable with ceftiofur influences the resistance pattern of intestinal Escherichia coli of the treated as well as untreated animals housed in the same stable. During therapy with the drug which was administered by injection according to the licence we detected nameable amounts of ceftiofur and its active metabolites in the dust and air of the stable.