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.     

土壤粒度对土霉素在黑土和红壤上吸附的影响

为了探明土壤粒度对土霉素在土壤上吸附的影响,以性质差异显著的黑土和红壤为供试土壤,采用批量平衡法,研究了土霉素在不同粒度的2种土壤上的吸附行为。结果表明：（1）土霉素在不同粒度土壤上的吸附均分为快吸附和慢吸附2个过程,土壤类型和不同粒度的同种土壤对土霉素吸附速率存在差异,Elovich模型、双常数模型对动力学吸附过程拟合效果最好;（2）3种等温吸附方程模型都可以较好地拟合研磨度不同的2种土壤对土霉素的吸附,相关系数（R^2）在0.954～0.999之间,吸附参数kd、kf在2种土壤上均随着粒度的减小而增大。因此,在研究土霉素等四环素类抗生素在土壤上的吸附时选择合适的土壤粒度非常重要。     

土壤中土霉素残留的高效液相色谱检测方法

为有效测定土壤中土霉素残留量,建立了固相萃取－高效液相色谱法提取以及测定潮土、红壤、紫色土中土霉素残留量的方法。土壤中土霉素残留经提取缓冲溶液进行有效提取,经过DVB固相萃取小柱纯化、无水甲醇洗脱和氮气流浓缩后,经HPLC测定。对提取缓冲液、流动相以及流动相pH值、有机相与无机相的比例以及流速等测定条件进行优化研究。结果表明：提取液为Na2EDTA-Mcllvaine,流动相为乙腈∶0.01mol/L磷酸二氢钠（pH值2.5,V∶V=10∶90）,温度25℃,流速1.2ml/min,检测波长350nm对3种不同性质的土壤中土霉素残留量的测定最为合适。应用本方法进行土壤中土霉素残留量的测定,土霉素含量与峰面积具有良好的线性关系,相关系数（n=9）分别为红壤0.997,紫色土0.995,潮土0.987;检出限分别为红壤0.11mg/kg,紫色土0.17mg/kg,潮土0.09mg/kg;回收率(n=18)分别为红壤80.7%~128.8%,紫色土70.5%~100.0%,潮土61.5%~103.9%;相对标准偏差(RSD, n=18)分别为红壤7.1%~28.2%,紫色土11.9%~38.1%,潮土4.1%~17.0％。本方法简便、准确,适合于测定不同土壤中土霉素残留量,结果可靠。     

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     

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...     

土霉素暴露对水培小麦生长及根际微生物的影响

采用水培法研究了土霉素(OTC)暴露对小麦(Triticum aestivum Linn.)生长和根际微生物群落结构的影响。结果表明,在设定的土霉素浓度下,小麦发芽率受抑制程度与处理浓度呈正相关,最大抑制率出现在处理浓度为100 mg/L时,达40%;土霉素对小麦根长和芽长的抑制效应显著(P0.05),时间和剂量效应明显。PCR-DGGE分析结果表明,0.8 mg/L和4.0 mg/L土霉素暴露对根际微生物群落结构影响较小,浓度在20.0 mg/L以上对微生物群落结构影响显著,出现新的优势种群。     

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.     

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.     

Lawsonia intracellularis proliferative enteropathy in a 3.5‐year‐old miniature horse

A 3.5‐year‐old miniature horse gelding was evaluated for signs of colic and decreased faecal production. Initial clinical pathology showed severe hypoproteinaemia with an albumin concentration <10 g/l. Abdominal ultrasound identified multiple loops of small intestine with significantly increased wall thickness. Diagnosis of equine proliferative enteropathy was based on clinical and laboratory findings, as well as a positive faecal polymerase chain reaction and positive antibody titre (>1:240) to Lawsonia intracellularis. Treatment with intravenous oxytetracylcine and additional supportive care gradually resolved the clinical and laboratory abnormalities.