Tetracyclines, which represent one of the most commonly used antibiotics for poultry, are known to be deposited in bones, where they can remain, despite the observation of appropriate withdrawal times. The aim of the study was to determine the concentration of oxytretracycline (OTC) residues in the bone and muscle of chickens, following the oral administration of a commercially available liquid formulation, and to test their cytotoxic effects on an in vitro cell culture model. Seventy-two 1-day-old broiler chickens were randomly allotted into 2 groups (control and treated animals). OTC (40 mg/kg BW) was administered via drinking water during the 1 to 5 and 20 to 25 days of life periods. At the end of the trial, the birds were slaughtered and the OTC residues in the target tissues were measured by means of liquid chromatography (LC) - tandem mass spectrometry (MS/MS). Cytotoxicity was assessed by evaluating the pro-apoptotic effect of the bone residues on the K562 erythroleukemic line and on the peripheral blood mononuclear cells (PBMC). In all the animals, the OTC residues in the muscle were far below the established MRL of 100 μg/kg. The OTC levels in the bones of the treated animals were instead found in the parts per million (ppm) range. Cell cytotoxicity was assessed by evaluating the pro-apoptotic effect of OTC bone residues on the haematopoietic cell system. This in vitro system has revealed a significant pro-apoptotic effect on both the K562 cell line and PBMC cultures. This result suggests potential human and animal health risks due to the entry of tetracycline residues contained in the bones of treated livestock into the food-chain. This could be of concern, particularly for canine and feline diets, as meat, bone meal, and poultry by-products represent some of the main ingredients of pet foods, especially in the case of dry pet food. Further studies are needed to define the underlying mechanisms of cytotoxicity and to evaluate the in vivo toxicological implications due to the observed in vitro effects.

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Antibiotics are widely used in zoo technical and veterinary practices as feed supplementation to ensure wellness of farmed animals and livestock. Several evidences have been suggesting both the toxic role for tetracyclines, particularly for oxytetracycline (OTC). This potential toxicity appears of great relevance for human nutrition and for domestic animals. This study aimed to extend the evaluation of such toxicity. The biologic impact of the drug was assessed by evaluating the proinflammatory effect of OTC and their bone residues on cytokine secretion by in vitro human peripheral blood lymphocytes. Our results showed that both OTC and OTC‐bone residues significantly induced the T lymphocyte and non‐T cell secretion of interferon (IFN)‐γ, as cytokine involved in inflammatory responses in humans as well as in animals. These results may suggest a possible implication for new potential human and animal health risks depending on the entry of tetracyclines in the food‐processing chain.

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BackgroundClinical appearance and evolution of Canine Leishmaniosis (CL) are the consequence of complex interactions between the parasite and the genetic and immunological backgrounds. We investigated the effect of an immune-modulating diet in CL. Dogs were treated with anti- Leishmania pharmacological therapy combined with standard diet (SD Group) or with the immune-modulating diet (IMMD Group). CD3+ CD4+ Foxp3+ Regulatory T cells (Treg) and CD3+ CD4+ IFN-γ + T helper 1 (Th1) were analyzed by flow cytometry.ResultsAll sick dogs showed low platelet number at diagnosis (T0). A platelet increase was observed after six months (T6) SD Group, with still remaining in the normal range at twelve months (T12). IMMD Group showed an increase in platelet number becoming similar to healthy dogs at T6 and T12. An increase of CD4/CD8 ratio was revealed in SD Group after three months (T3), while at T6 and at T12 the values resembled to T0. The increase in CD4/CD8 ratio at T3 was maintained at T6 and T12 in IMMD Group.A reduction in the percentage of Treg of all sick dogs was observed at T0. A recovery of Treg percentage was observed only at T3 in SD Group, while this effect disappeared at T6 and T12. In contrast, Treg percentage became similar to healthy animals in IMDD Group at T3, T6 and T12. Sick dogs showed an increase of Th1 cells at T0 as compared with healthy dogs. We observed the occurrence of a decrease of Th1 cells from T3 to T12 in SD Group, although a trend of increase was observed at T6 and T12. At variance, IMMD Group dogs showed a progressive decrease of Th1 cells, whose levels became similar to healthy controls at T6 and T12.ConclusionThe immune-modulating diet appears to regulate the immune response in CL during the standard pharmacological treatment. The presence of nutraceuticals in the diet correlates with the decrease of Th1 cells and with the increase of Treg in sick dogs. Therefore, the administration of the specific dietary supplement improved the clinical response to the standard treatment in a model of CL.