RESUMEN
Essential oils (EO) are a great antimicrobial resource against bacterial resistance in public health. Math models are useful in describing the growth, survival, and inactivation of microorganisms against antimicrobials. We evaluated the antimicrobial activity of Melaleuca armillaris EO obtained from plants placed in the province of Buenos Aires (Argentina) against Staphylococcus aureus. The minimum inhibitory and bactericidal concentrations were close and decreased, slightly acidifying the medium from pH 7.4 to 6.5 and 5.0. This result was also evidenced by applying a sigmoid model, where the time and EO concentration necessaries to achieve 50% of the maximum effect decreased when the medium was acidified. Moreover, at pH 7.4, applying the Gompertz model, we found that subinhibitory concentrations of EO decreased the growth rate and the maximum population density and increased the latency period concerning the control. Additionally, we established physicochemical parameters for quality control and standardization of M. armillaris EO. Mathematical modeling allowed us to estimate key parameters in the behavior of S. aureus and Melaleuca armillaris EO at different pH. This is interesting in situations where the pH changes are relevant, such as the control of intracellular infections in public health or the development of preservatives for the food industry.
RESUMEN
Helminth infections are widespread in the poultry industry. There is evidence of extra-label use of some drugs, such as ivermectin (IVM), in broiler poultry. Pharmacokinetic and residual studies of IVM in poultry, however, are rather scarce. Our aim was to determine time restrictions for broiler chickens fed with balanced feed mixed with IVM for 21 days, and thus achieve acceptable residual levels for consumption as established by the European Union. Sixty 1-day-old chicks were fed with food supplemented with IVM at 5 mg kg-1 feed for 21 days. Groups of six treated animals were sacrificed at 0, 1, 2, 4, 8, 10, 15, 20 and 28 days after treatment. Liver, skin/fat, kidney and muscle samples were obtained. IVM were determined by liquid chromatography with fluorescence detection after automatic solid-phase extraction with SPE C18 cartridges. The highest concentrations were measured in the liver, which is logical given that IVM is a drug that undergoes extensive hepatic metabolism. The optimal withdrawal time for edible tissues of these animals to stay within the permitted residual levels were: 12 days for liver, 8 days for skin/fat, 0 days for muscle and 10 days for kidney.
Asunto(s)
Antihelmínticos/análisis , Residuos de Medicamentos/análisis , Ivermectina/análisis , Carne/análisis , Ingesta Diaria Recomendada/legislación & jurisprudencia , Tejido Adiposo/química , Animales , Antihelmínticos/administración & dosificación , Antihelmínticos/metabolismo , Antihelmínticos/farmacocinética , Pollos , Cromatografía Liquida , Residuos de Medicamentos/metabolismo , Unión Europea , Guías como Asunto , Humanos , Ivermectina/administración & dosificación , Ivermectina/metabolismo , Ivermectina/farmacocinética , Riñón/química , Hígado/química , Músculos/química , Piel/química , Extracción en Fase Sólida/métodos , Espectrometría de Fluorescencia , Factores de TiempoRESUMEN
The aim of this study was to evaluate the bioequivalence of two commercial long-acting formulations based on oxytetracycline (OTC) hydrochloride between the reference formulation (Terramycin LA, Pfizer) and a test formulation (Cyamicin LA, Fort Dodge Saude Animal). Both formulations were administered in a single intramuscular route at a dose of 20 mg OTC/kg of body weight in clinically healthy bovines. The study was carried out according to a one-period parallel design. Plasma samples were analyzed by high-pressure liquid chromatography. The limit of quantitation was 0.050 µg/mL with an accuracy of 101.67% with a coefficient of variation of 13.15%. Analysis of variance and 90% confidence interval tests were used to compare the bioavailability parameters (maximum plasma concentration, C max, and the area under the concentration-versus-time curve extrapolated to infinity, AUC0-∞) of both products. In the case of the time to maximum concentration (T max), non-parametric tests based on Wilcoxon's signed rank test were preferred. The comparison of the mean AUC0-∞ values did not reveal any significant differences (311.40 ± 93.05 µg h/mL and 287.71 ± 45.31 µg h/mL, respectively). The results were similar for the T max (3.58 ± 0.90 h versus 3.42 ± 0.51 h). However, when comparing the mean C max some significant differences were found (8.73 ± 3.66 µg/mL and 10.43 ± 3.84 µg/mL, respectively). The 90% confidence intervals for the ratio of AUC0-∞ and T max values for the reference and test product are within the interval 80-125%, but the 90% confidence intervals for the ratio of C max falls outside the proposed interval. It was concluded that C max of test product are not within the 20% of those of the reference, thus suggesting that test OTC is not bioequivalent to the reference formulation.