反相高效液相色谱法测定牛奶中土霉素残留

建立了测定牛奶中土霉素残留的RP-HPLC方法.采用草酸甲醇液提取牛奶中的土霉素,离心,用C18色谱柱(5 μm,250 mm×4.6 mm),甲醇 乙腈 0.01 mol/L草酸溶液(20∶ 12∶ 68)为流动相,流速1 mL/min,检测波长360 nm,以HPLC外标法测定牛奶中土霉素的残留量.结果:土霉素峰面积与浓度呈良好的线性关系,其线性范围为50～1 500 μg/L(r=0.999 9),平均回收率为88%.本法简便、准确、快速,是一种较好的测定牛奶中土霉素残留的方法.     

Some Pharmacokinetic Parameters and Dosage Regimens for a Long-Acting Formulation of Oxytetracycline in 6- to 8-Month-Old Male Calves

A two-way crossover study was conducted in crossbred male calves (6–8 months old) to determine the bioavailability, pharmacokinetics and dosage regimens for a long-acting formulation of oxytetracycline (OTC-LA). The half-lives of oxytetracycline after intravenous and intramuscular administration were 7.8 h and 24 h, respectively. The volume of distribution and total body clearance values of the drug were 0.86±0.07 L and 76.1±3.3 (ml/h)/kg, respectively. The maximum concentration of the drug in the serum (4.7–7.4 g/ml) was achieved 8–10 h after intramuscular administration. The minimum therapeutic serum concentration of drug of 0.5 g/ml was maintained between 15 min and 84 h after intramuscular administration. The intramuscular bioavailability of the drug was 89.1±4.2%. The dosage regimens to maintain the minimum therapeutic serum concentrations of OTC following intramuscular administration of OTC-LA were computed.     

Bioequivalence Study of Two Long-acting Oxytetracycline Formulations in Sheep

Two commercially available long-acting oxytetracycline hydrochloride formulations (Primamycin LA (Pfizer) and Terralent 20% LA (İ.E. Ulagay)) were administered by the intramuscular route to 20 clinically healthy sheep at a dose of 20 mg/kg. The study was performed in a two-period crossover design. Plasma samples were analysed by high-pressure liquid chromatography. The mean maximum concentrations (C _max) was 8.00 ± 2.05 μg/mland 8.61 ± 1.42 μg/ml, respectively. The mean area under the concentration time curve (AUC) values were 154.95 ± 50.37(μg h)/ml and 161.70 ± 47.02(μg h)/ml, respectively. The 90%confidence intervals for the ratio of C _max and AUC values for the test and reference product are with in the interval 70−143% for C _max and interval 80-−125% for AUC proposed by EMEA. It was concluded that Primamycin LA and Terralent 20% LA formulations are bioequivalent in their rate and extent of drug absorbtion. Ozdemir N. and Yıldırım, M., 2006. Bioequivalence study of two long-acting oxytetracycline formulations in sheep. Veterinary Research Communications, 30(8), 929–934     

Interplay Between Oxytetracycline and the Homozygote kdr (L1014F) Resistance Genotype on Fecundity in Anopheles gambiae (Diptera: Culicidae) Mosquitoes

The insecticide resistance in Anopheles gambiae mosquitoes has remained the major threat for vector control programs but the fitness effects conferred by these mechanisms are poorly understood. To fill this knowledge gap, the present study aimed at testing the hypothesis that antibiotic oxytetracycline could have an interaction with insecticide resistance genotypes and consequently inhibit the fecundity in An. gambiae. Four strains of An. gambiae: Kisumu (susceptible), KisKdr (kdr (L1014F) resistant), AcerKis (ace-1 (G119S) resistant) and AcerKdrKis (both kdr (L1014F) and ace-1 (G119S) resistant) were used in this study. The different strains were allowed to bloodfeed on a rabbit previously treated with antibiotic oxytetracycline at a concentration of 39·10^–5 M. Three days later, ovarian follicles were dissected from individual mosquito ovaries into physiological saline solution (0.9% NaCl) under a stereomicroscope and the eggs were counted. Fecundity was substantially lower in oxytetracycline-exposed KisKdr females when compared to that of the untreated individuals and oxytetracycline-exposed Kisumu females. The exposed AcerKis females displayed an increased fecundity compared to their nontreated counterparts whereas they had reduced fecundity compared to that of oxytetracycline-exposed Kisumu females. There was no substantial difference between the fecundity in the treated and untreated AcerKdrKis females. The oxytetracycline-exposed AcerKdrKis mosquitoes had an increased fecundity compared to that of the exposed Kisumu females. Our data indicate an indirect effect of oxytetracycline in reducing fecundity of An. gambiae mosquitoes carrying kdr^R (L1014F) genotype. These findings could be useful for designing new integrated approaches for malaria vector control in endemic countries.     

土霉素处理对Valencia夏橙中淀粉及相关基因表达的影响

黄龙病(Huanglongbing,HLB)会造成柑橘韧皮部坏死堵塞,导致光合同化物运输不畅,淀粉大量积累。在感染HLB的4年生Valencia夏橙病株上分别注入0.1和0.2 g·株~(-1)土霉素(Oxytetracycline,OTC),90 d后运用qPCR检测,病株中HLB病原菌(Candidatus Liberibacter asiaticus,Las)含量均明显降低,且0.2和0.1 g·株~(-1) OTC处理的效果相当。I2/KI显色及LM观测表明,0.2 g·株~(-1) OTC处理后植株的淀粉含量从注射前的18.58μg·mm~(-2)减少至90 d的5.24μg·mm~(-2),而0.1 g·株~(-1)的处理90 d仅降至11.88μg·mm~(-2)。高效液相色谱(HPLC)检测结果表明,注射后90 d内,试验用浓度0.2 g·株~(-1) OTC在植株体内可降解至200μg·kg~(-1)以下。基因表达结果表明,注射0.2 g·株~(-1) OTC后30和90 d,淀粉合成及分解相关基因表达量均下降,其中淀粉合成相关基因AGPase表达量下降最显著,这与OTC注射后30和90 d叶片内淀粉含量下降结果一致。     

土霉素在鸡粪中的残留及降解规律研究

检测了健康肉鸡以不同剂量土霉素混饲给药后,在不同时间鸡粪中土霉素的含量变化,并比较避光及人工光照条件下灭菌鸡粪中土霉素的降解规律,以及在避光条件下灭菌、未灭菌及灭菌后加降解菌处理,鸡粪中土霉素的降解规律。结果表明,健康肉鸡混饲给予土霉素(100、200、400mg·kg-1)后,鸡粪中土霉素排泄量在给药后6～8h达到高峰,峰浓度分别为13.58、36.15mg·kg-1和50.73mg·kg-1,并于30、62h和72h时检测不到土霉素;对鸡粪中土霉素的浓度随时间变化趋势进行曲线拟合,发现各处理组的这种变化趋势均符合一级动力学方程Ct=C0e-kt。经灭菌鸡粪中土霉素的降解受光照条件和土霉素初始浓度的影响,初始浓度为10、20、40mg·kg-1时,避光条件下,土霉素降解半衰期分别为55.5、123.8d和173.3d;人工光照条件下,鸡粪中的土霉素降解较快,降解半衰期分别为14.8、21.1d和27.5d。此外,无论是在避光还是人工光照条件下,较高初始浓度组的土霉素降解速率均比较低初始浓度组慢。去除光照因素后,鸡粪中所含土霉素的降解主要受微生物及土霉素初始浓度的影响,初始浓度为10、20、40mg·kg-1...     

Effects of Oxytetracycline on Methane Production and the Microbial Communities During Anaerobic Digestion of Cow Manure

The effects of different concentrations of oxytetracycline （OTC） on the dynamics of bacterial and archaeal communities during the mesophilic anaerobic digestion （37＆#176;C） of cow manure were investigated. Before anaerobic digestion, OTC was added to digesters at concentrations of 20, 50, and 80 mg L-1, respectively. Compared with no-antibiotic control, all methane productions underwent different levels of inhibition at different concentrations of OTC. Changes in the bacterial and archaeal communities were discussed by using PCR-denaturing gradient gel electrophoresis （DGGE）. Results showed that OTC affected the richness and diversity of bacterial and archaeal communities. The bacterial genus Flavobacterium and an uncultured bacterium （JN256083.1） were detected throughout the entire process of anaerobic digestion and seemed to be the functional bacteria. Methanobrevibacter boviskoreani and an uncultured archaeon （FJ230982.1） dominated the archaeal communities during anaerobic digestion. These microorganisms may have high resistance to OTC and may play vital roles in methane production.     

The impacts of oxytetracycline on humification during manure composting can be alleviated by adjusting initial moisture contents as illustrated by NMR

Oxytetracycline(OTC) residues have been found in soil and water, and they may pose potential risks to agricultural ecological environments. One of the most impactful ways for OTC to enter the soil and water environments is through excrement used as organic fertilizer. Therefore, it is important to remove OTC during manure composting and to understand the transformation of the organic materials during composting in the presence of OTC. In the present paper, chicken manure and wheat sawdust spiked with OTC were composted under different initial moisture contents(MC) to evaluate the degradation of OTC and changes of organic matter during the composting process. The MC has a significant effect on OTC degradation during composting. A higher MC of 65% was more conducive to OTC degradation(77.4%) and compost maturity compared to the lower MC. However, the higher MC of 65% could increase the ammonia volatilization by promoting nitrification compared to the lower MC. An increase in the initial MC could improve the composting temperature. NMR results illustrated that the presence of OTC could affect the internal transformation of aliphatics, and OTC inhibited compost humification. Thus, an initial MC of 55–65% can alleviate the impacts of OTC on humification during manure composting.     

Degradation mechanisms of oxytetracycline in the environment

Over the past few decades, the usage of oxytetracycline(OTC), a kind of antibiotic, has increased with the development of aquaculture and livestock breeding. However, about 30–90% of the applied antibiotics are excreted as the parent compounds into the environment, especially with the application of animal manure to agricultural fields. This large influx of antibiotics may lead to the destruction of the natural microbial ecological community and pose great threats to human beings through the food chain. Therefore, the fate and toxicity of OTC in the environment are issues of great concern. Degradation of OTC, including the non-biodegradation and biodegradation, and the biological toxicity of its degradation products or metabolites, are reviewed in this paper. The non-biodegradation pathways include hydroxylation, quinonization, demethylation, decarbonylation, dehydration and secondary alcohol oxidation. Light(particularly UV light), pH and oxidizing substances play important roles in non-biodegradation. Biodegradation products include 4-epi-OTC(EOTC), 2-acetyl-2-decarboxy-amido-OTC(ADOTC), α-apo-OTC and β-apo-OTC. EOTC is an epimer and identied except for the configuration of the C4 dimethylamino group of OTC. Temperature and pH are the main factors affecting biodegradation pathways of OTC. In addition, this review discusses concerns over the biological toxicity of OTC degradation products.