合成甲氧苄氨嘧啶缩合产物同分异构体的分析和转化工艺研究

对以三甲氧基苯甲醛为原料合成甲氧苄氨嘧啶(TMP)的缩合产品中的同分异构体2-甲氧甲基-3-(3,4,5-三甲氧苯基)-丙烯腈(Ⅰ)和2-(3,4,5-三甲氧基苄基)-3-甲氧基丙烯腈(Ⅱ)的相对含量提出了用高效液相色谱分析的方法,其中色谱柱为C18柱,流动相为四氢呋喃-水(体积比为30∶70),检测波长为320 nm。并对同分异构体的相互转化工艺进行了优化,当缩合产品的用量为15 g时,甲醇钠用量为27 mL,用35 mL无水乙醇或乙二醇单甲醚作溶剂,一次回流温度和时间为80°C和2 h,二次回流温度和时间分别为84~86°C和3 h时,其中可进行环合反应所需的同分异构体Ⅱ的相对含量转化至99%以上。     

Differential patterns of antimicrobial resistance in population subsets of Escherichia coli isolated from waste- and surface waters

The species Escherichia coli comprises different subgroups with distinct phylogeny, physiology and ecology and, thus, presumably, with different roles in antimicrobial resistance dissemination. E. coli strains isolated from raw and treated municipal wastewater and from urban water streams were characterized in terms of phylogenetic groups, antimicrobial resistance patterns and the presence of class 1 and class 2 integrons. Our main objective was to investigate the contribution of the different phylo-groups in antimicrobial resistance dissemination in urban waters. Groups A and B1 were predominant in all types of water, evidencing, respectively, the lowest and the highest resistance prevalence. Municipal wastewater treatment was accompanied by significant increases of ciprofloxacin and streptomycin resistance (p < 0.01). Antimicrobial resistance prevalence differed significantly between the different phylo-groups and within the same group, mainly in group A. Such differences contributed to explain the higher ciprofloxacin and streptomycin resistance rates observed in treated effluent in comparison with the raw wastewater. We conclude that the dynamics of the bacterial populations has a major role on the dissemination of antimicrobial resistance in the environment.     

Prevalence and antimicrobial resistance of Salmonella isolated from an integrated broiler chicken supply chain in Qingdao,China

The present study analyzed the prevalence and antimicrobial resistance of Salmonella along an integrated broiler chicken supply chain. A total of 172 Salmonella isolates were recovered from 1148 samples collected from four sample sources (breeder farms, broiler farms, abattoir, and retail markets), representing nine production stages. These Salmonella isolates were examined for antimicrobial susceptibility to 12 different antimicrobial agents using a disk diffusion assay. Among them, 168 were identified as six different serotypes of Salmonella enterica. The predominant serotype was S. Enteritidis (n = 116), followed by S. Infantis (n = 18), S. Gueuletapee (n = 16), S. Derby (n = 12), S. Meleagridis (n = 4), and S. London (n = 2). The remaining four isolates were serogroup-untypeable. A majority of the 172 isolates (96.51%) was resistant to one or more antibiotics and 61.05% of the Salmonella isolates showed a multidrug resistance phenotype. Statistical analysis indicated the one risk product stage for Salmonella contamination occurred in the sample source at the abattoir, specifically the stage of Carcasses after chilling. The majority of S. Enteritidis isolates shared the same pulsed-field gel electrophoresis (PFGE) cluster, suggesting that the S. Enteritidis strain might spread along the broiler chicken supply chain. The prevalence and antimicrobial resistance of Salmonella in different production stages suggest the importance of controlling Salmonella in the broiler chicken supply chain for public health, underlying the need for improved measures of reducing carcass contamination in abattoirs and the appropriate use of antimicrobials in broiler flocks.     

高效液相色谱法测定水产品中残留的甲氧苄啶

建立测定水产品中残留的甲氧苄啶的高效液相色谱法。样品经三氯甲烷和酸性甲醇溶液提取,提取液调至碱性后用二氯甲烷萃取,萃取液经MCX 柱净化,洗脱液浓缩至近干后用流动相溶解,过微孔滤膜,采用高效液相色谱紫外检测,外标法定量。结果表明,甲氧苄啶在0.05～5.0μg/mL 质量浓度范围内,色谱峰面积与甲氧苄啶质量浓度之间线性关系良好(相关系数为0.999967),在空白样品的20、40、200μg/kg 3 个加标量条件下,样品平均回收率均大于80%,相对标准偏差小于7%,方法的检测限为20μg/kg。该方法简便快速,基体干扰小,精密度、准确性均能满足水产品中甲氧苄啶的残留分析。     

紫外分光光度法同时测定复方磺胺甲噁唑片组分含量

用人工神经网络解析复方磺胺甲噁唑片的紫外吸收光谱数据,达到同时测定各组分含量的目的。按L25（5^6）正交表设计,制备了25组标准溶液的混合液,将其吸光度数据和浓度数据作为人工神经网络的训练集。混合液中各组分的5个浓度水平分别为80％、90％、100％、110％、120％。预报集采用自制的模拟样品和市售的复方磺胺甲噁唑片的吸光度数据。网络的输入为各溶液在246～290nm间的吸光度,网络的输出为各组分的浓度。利用Bayesian规则化调整的BP人工神经网络处理数据。结果表明,人工神经网络紫外分光光度法预测模拟样品中的磺胺甲噁唑（SMZ）、甲氧苄啶（TMP）的含量,平均回收率分别为100．53％和100．91％,相对标准偏差分别为1．17％和2．79％。对市售的复方磺胺甲噁唑片中的SMZ、TMP的含量也能取得较好的预测结果。结论：人工神经网络紫外分光光度法可以快速、准确地测定复方磺胺甲噁唑片中组分含量。     

复方替米考星纳米乳的制备及其质量评价

研制了复方替米考星纳米乳(TMS-TMPL-NE)并对其进行了质量评价。通过绘制伪三元相图优选处方,以肉豆蔻异丙酯(IPM)为油相,吐温80为表面活性剂,m(无水乙醇)/m(1,2-丙二醇,PG)=3为助表面活性剂,磷酸为增溶剂,制备了TMS-TMPL-NE,用透射电子显微镜(TEM)、Nicomp388/ZetaPALS激光粒度测定仪分别考察了其形态和粒径,通过恒温加速实验检验了其稳定性。纳米乳在透射电镜下呈圆球形,分布均匀,粒径为12.4nm,多分散系数(PDI)为0.051,恒温加速实验结果显示其未分层,仍为澄清透明纳米乳状液。TMS-TMPL-NE稳定性好,制备工艺简单,有望应用于兽医临床。     

高效液相色谱法测定甲氧苄啶氯化钠注射液中甲氧苄啶的含量

建立了甲氧苄啶氯化钠注射液中甲氧苄啶含量的HPLC测定方法。本法采用C18色谱柱,流动相为0.1mol/L磷酸二氢钾溶液(用磷酸调节pH值至2.5)-甲醇的混合溶液(按v∶v=70∶30配制),检测波长为280nm,流速为1.0mL/min。实验数据表明:甲氧苄啶在0.38～1.37μg的范围内,峰面积与进样量呈良好线性关系(r=0.9995),回收率RSD=0.69%,最低检测限为1ng,分析结果准确,可用于测定甲氧苄啶氯化钠注射液中甲氧苄啶含量。     

N+离子注入诱变筛选胸腺嘧啶缺陷型大肠杆菌

利用N+离子注入诱变大肠杆菌,经甲氧苄啶的选择性筛选,得到胸腺嘧啶营养缺陷型菌株.通过重组DNA技术将该突变株胸苷酸合成酶(TS)基因连接到载体pMD-18T质粒上,经测序发现TS基因第173个碱基由AT→CG,其相应的氨基酸由谷氨酸(E58)突变为丙氨酸(A58).该突变株的获得为后续研究嘧啶核苷酸的代谢奠定了基础.     

超高效液相色谱质谱法快速检测动物源性食品中的四种兽药残留

建立了采用超高效液相色谱串联质谱仪快速检测动物组织中甲氧苄胺嘧啶、克林霉素、泰妙菌素和吡喹酮四种药物残留的分析方法。动物组织样品经乙腈提取后,用正己烷去除脂肪等杂质,Waters Acquily UPLC BEH C18色谱柱分离,以乙腈和0.1%甲酸水溶液为流动相进行梯度洗脱,电喷雾正离子（ESI+）模式电离,液相色谱-质谱法（UPLC-MS/MS）测定。结果表明:4种药物在2.5～200μg/L范围内呈现良好的线性关系,相关系数R2均大于0.996,在此范围内添加回收率为65.8%⁹5.9%,相对标准偏差为3.2%¹3.1%,定量下限为0.5μg/kg。      

高效液相色谱法测定动物组织中甲氧苄氨嘧啶的残留量

建立测定动物组织中甲氧苄氨嘧啶残留量的高效液相色谱方法.以二氯甲烷-乙腈(1 10)在碱性条件下提取,稀硫酸反提,正己烷分配,Oasis(R)HLB 小柱净化,流动相溶解,紫外检测器 240 nm 进行检测,流动相为醋酸铵溶液-乙腈-甲醇(70:22:8)体系,流速 1.1 mL/min,C18柱富集.检测限最低达到10 μg/kg,线性在 25～300 μg/kg 良好,平均回收率较高.