高效液相色谱法测定鸡蛋中4种氟喹诺酮类 药物的含量

目的采用高效液相色谱法同时测定鸡蛋中环丙沙星、恩诺沙星、沙拉沙星和达氟沙星4种药物的残留量。方法样品经磷酸盐提取液提取后,经反相C_(18)柱分离,采用0.05 mol/L磷酸-三乙胺溶液:乙腈(85:15,V:V)流动相进行等度洗脱,流速为0.8 m L/min,采用荧光检测器在激发波长280 nm、发射波长450 nm的条件下进行测定,以外标法定量。结果环丙沙星、恩诺沙星和沙拉沙星在0.005~0.5μg/m L、达氟沙星在0.001~0.1μg/m L浓度范围内具有良好的线性关系,相关系数为0.9998,加标回收率为96.5%~103%,相对标准偏差为0.83%~1.28%。结论该方法精确可靠,重复性、稳定性和分离效果好,可适用于测定鸡蛋中氟喹诺酮类药物的残留量。     

鸡肉源沙门氏菌对(氟)喹诺酮类抗生素的耐药性及相关基因

目的:研究分离于广东、广西、福建和上海4省(市)零售鸡肉源沙门氏菌对萘啶酮酸和部分氟喹诺酮类抗生素的药敏性及相关耐药基因,以更好地了解耐药性的产生和传播途径,确保食品安全。方法:使用临床和实验室标准协会推荐的琼脂稀释法测定沙门氏菌的药敏性,用PCR、基因序列测定和基因库在线比对方法确定耐药沙门氏菌中与(氟)喹诺酮类抗生素耐药相关的gyr A亚基中喹诺酮类抗性决定区,par C亚基中的氨基酸突变状况以及qnr质粒携带的与喹诺酮类抗生素耐药相关基因。结果:358株沙门氏菌中,59.78%的菌株对萘啶酮酸产生抗性,对环丙沙星、左氧氟沙星和加替沙星耐药的菌株比例分别为22.91%,17.88%和16.20%。214株萘啶酮酸抗性菌中,qnr A,qnr B,qnr S和aac(6′)-Ib-cr基因的检出率分别为11.68%,18.22%,3.27%和24.77%。82株环丙沙星抗性菌中,从gyr A和par C基因中共检出135个氨基酸突变点,其中从gyr A基因中检出65个突变点,从par C基因中检出70个突变点。gyr A基因中以Asp87Asn突变最为常见(47.69%;31/82),其次分别为Asp87Gly(38.46%,25/82),Asp87Tyr(4.62%,3/82),Ser83Phe和Asp87Asn双突变(3.80%,1/82),Asp87Asn和Ile89Val双突变(3.80%,1/82),Asp87Asn和Val90Gly双突变(3.80%,1/82)。par C基因中Ser80Arg突变最为常见(90.00%,63/82),其次分别为Met118Ile-Arg119Leu-Thr121Ser三突变(4.29%,1/82),Ser80Arg和Tyr120Phe双突变(2.86%,1/82),Ser80Ile(1.43%,1/82)和Ala81Val(1.43%;1/82)。结论:4省市中鸡肉源沙门氏菌对萘啶酮酸和部分氟喹诺酮类抗生素耐药严重,其中解旋酶和拓扑异构酶基因突变以及沙门氏菌携带的qnr A,qnr B,qnr S和aac(6′)-Ib-cr基因是沙门氏菌耐药的重要原因。     

微波辅助萃取-液相色谱-串联质谱法检测猪肉中四种氟喹诺酮类药物残留

建立了微波辅助萃取-液相色谱-串联质谱法检测猪肉中氧氟沙星、诺氟沙星、环丙沙星、恩诺沙星四种氟喹诺酮类药物残留的方法。样品经微波辅助萃取,正己烷脱脂,无水硫酸钠除水,浓缩提取物至干,用1.0mL0.1%甲酸溶液溶解后上机检测。采用Hypersil GOLD-1.9μm,50 mm×2.1 mm(i.d)色谱柱分离,在多反应监测模式下检测,外标法定量。结果表明:四种氟喹诺酮类药物在浓度10～200μg/L范围内线性关系良好,相关系数r=0.9956～0.9991,定量限为10μg/kg。在不同添加水平下,其平均回收率为88%～101%,变异系数为1.4%～4.1%。     

Functional Gelatin-Carbon Nanotubes Nanohybrids With Enhanced Antibacterial Activity

Hybrid materials with enhanced antibacterial activity were prepared by incorporation of carbon nanotubes within gelatin-fluoroquinolones bioconjugates. Gelatin bioconjugates were characterized by UV-Vis, FT-IR, and calorimetric analyses, nanohybrids by morphological analyses. Biocompatibility was evaluated on human mesenchymal stem cells, and antibacterial performance against Klebsiella pneumoniae and Escherichia coli. Minimun inhibitory concentrations from 0.025 to 0.05 µg mL^?1 and from 0.025 to 0.10 µg mL^?1, and MBC from 0.025 to 0.10 µg mL^?1 and from 0.05 to 0.20 µg mL^?1 were detected for Escherichia coli and Klebsiella pneumoniae, respectively, showing that nanotubes increase antimicrobial activity comparing to both free and gelatin-conjugated drugs.     

A simple method for the determination of fluoroquinolone residues in tilapia (Oreochromis niloticus) and pacu (Piaractus mesopotamicus) employing LC-MS/MS QToF

The use of antimicrobials in livestock production is a powerful resource applied throughout the world to guarantee high yield and control bacterial diseases in aquaculture. However, residues of these substances in animal products represent a potential risk to consumer health when residue levels are above the established maximum residue limits (MRLs). Fluoroquinolones (FQs) are antimicrobials commonly used worldwide in aquaculture. The aim of this work was to develop and validate a simple analytical method for the simultaneous determination of norfloxacin, danofloxacin, enrofloxacin and ciprofloxacin levels in tilapia (Oreochromis niloticus) and pacu (Piaractus mesopotamicus) fillets using liquid chromatography–tandem mass spectrometry (LC-MS/MS) quadrupole time of flight (QToF). The FQs were extracted from the fillets with 1% acetic acid–methanol and 1% acetic acid–acetonitrile solutions using ultrasonic assistance. The clean-up was performed with hexane. Chromatographic separation was conducted in an XTerra RP18 column (2.1 × 150 mm, 5 µm) at 25 °C with a flow of 0.2 mL min^?1. The mobile phase consisted of 0.1% aqueous formic acid and acetonitrile, with gradient elution. The validation parameters for all FQs were linearity (>0.99), intra-day precision (CV of 1%–9%), inter-day precision (CV of 3%–17%), decision limit (63–126 ng g^?1), detection capability (76 –152 ng g^?1) and accuracy (90%–111%). The limit of quantification was lower than the MRL for each FQ, indicating that the method is suitable for the determination of the FQ levels in the fish fillets. The mass analyser of the QToF type was able to confirm the identities of the FQs with an error of the accuracy of the mass (reasons m/z) of less than 10 ppm.     

Gemifloxacin mesylate (GFM): dissolution test based on in vivo data

Gemifloxacin mesylate (GFM) is a synthetic, broad-spectrum, fluoroquinolone antibacterial agent. It is different from other class members because it achieves adequate plasma concentrations to inhibit both topoisomerase IV and gyrase. The aim of this study was to develop and validate a dissolution test for GFM in coated tablets, using a simulated absorption profile based on in vivo data obtained from the literature. The fraction and percentage of the dose absorbed were calculated using model-dependent Loo-Riegelman approach for two compartments. The best in vitro dissolution profile was obtained using 900?mL of pH 6.0 phosphate buffer as a dissolution medium at 37?°C?±?0.5?°C and paddles at 50?rpm. The in vitro dissolution samples were analyzed using a liquid chromatography method, and the validation was performed according to USP 34 (2011). The method showed specificity, precision, accuracy, robustness and linearity. Under these conditions, a level-A in vitro–in vivo correlation was suggested (r?=?0.9926). The prediction errors were calculated to determine the validity and accuracy of the suggested correlation. The dissolution test can be used to evaluate the dissolution profile of GFM-coated tablets and minimize the number of bioavailability studies as part of new formulation development.     

液相色谱-串联质谱法检测中兽药中非法添加氟喹诺酮类药物含量的不确定度评估

目的评估液相色谱-串联质谱法检测中兽药中非法添加氟喹诺酮类药物含量的不确定度。方法建立液相色谱-串联质谱法检测中兽药(肥猪散、健胃散、银翘散)中非法添加氟喹诺酮类药物的含量测定方法,根据JJF1059.1-2012《测量不确定度评定与表示》的相关规定,对该方法的不确定度进行评定。结果中兽药中氟喹诺酮类药物含量分别为C(Enro)=100.90 mg/kg、C(Cip)=100.34 mg/kg、C(Norf)=100.21 mg/kg、C(Oflo)=100.61 mg/kg时,95%置信水平下,取k=2,不确定度评估结果分别表示为X(Enro)=(100.90±6.957)mg/kg;X(Cip)=(100.34±7.067) mg/kg; X(Norf)=(100.21±6.898) mg/kg; X(Oflo)=(100.61±6.957) mg/kg。结论评定结果表明,影响检测结果的主要因素为液相色谱-串联质谱仪的灵敏度、天平的精密度、操作的规范性。     

快速溶剂萃取-高效液相色谱-紫外串联荧光检测法测定太平湖白鱼中4种氟喹诺酮类药物残留

目的利用快速溶剂萃取(ASE),反相高效液相色谱-紫外串联荧光检测技术,建立了检测太平湖白鱼中4种氟喹诺酮类药物残留的定量分析方法。方法以8%氨水乙腈作为提取溶剂,对样品中的氟喹诺酮类药物采用快速溶剂萃取仪提取,萃取液经正己烷和乙醚去脂净化,用高效液相色谱-紫外串联荧光检测器测定,外标法定量。结果试样在10～200μg/L范围内校正曲线呈良好的线性关系,4种物质的相关系数都在0.999以上。当添加水平为255、0μg/kg时,鱼肉中4种氟喹诺酮类药物的加标回收率在82.7%～95.6%,相对标准偏差在2.1%～4.1%(n=5),检出限为1.3～3.0μg/kg。结论方法快速,操作简便,准确可靠,可以用于白鱼实际样品中氟喹诺酮类药物的日常检测。     

Determination of aminoglycosides and quinolones in food using tandem mass spectrometry: a review

The widespread use of antibiotics in dairy cattle management may result in the presence of antibiotic residues in food. While rapid screening tests are commonly used to detect the presence of antibiotics in food, more accurate chromatographic-mass spectrometric methods combined with tandem mass spectrometry (MS/MS) are required to determine the identity and quantity of the antibiotic present. These methods (HPLC/MS/MS) may have the greatest potential for accomplishing direct multi-residue identifications in complex biological matrices, such as food. This study reviews recent applications of tandem mass spectrometry in the determination of antibiotic residues, such as aminoglycosides and quinolones in food.     

Mechanism of binding of fluoroquinolones to the quinolone resistance-determining region of DNA gyrase: towards an understanding of the molecular basis of quinolone resistance

We have studied the bacterial resistance to fluoroquinolones that arises as a result of mutations in the DNA gyrase target protein. Although it is known that DNA gyrase is a target of quinolone antibacterial agents, the molecular details of the quinolone-gyrase interaction remain unclear. The mode of binding of ciprofloxacin, levofloxacin, and moxifloxacin to DNA gyrase was analyzed by means of docking calculations over the surface of the QRDR of GyrA. The analysis of these binding models allows study of the resistance mechanism associated with gyrA mutations more commonly found in E. coli fluoroquinolone-resistant strains at the atomic level. Asp87 was found to be critical in the binding of these fluoroquinolones because it interacts with the positively charged nitrogens in these bactericidal drugs. The role of the other most common mutations at amino acid codon Ser83 can be explained through the contacts that the side chain of this residue establishes with fluoroquinolone molecules. Finally, our results strongly suggest that, although Arg121 has never been found to be associated with fluoroquinolone resistance, this residue makes a pivotal contribution to the binding of the antibiotic to GyrA and to defining its position in the QRDR of the enzyme.