LC-MS/MS measurement of ampicillin residue in swine tissues at 5 days after in-feed administration

We assessed ampicillin (ABPC) concentrations of kidney, muscle and intestine after a 5–day withdrawal period in 2 male and a female young Large White pigs fed the diet containing ABPC (ABPC medicated feed, 24 mg/kg/day) for a week. The ABPC residues were measured with liquid chromatography–tandem mass spectrometry, and the mean recoveries and quantitation limits ranged from 91.8 to 97.2% and from 0.1 to 0.12 ng/g, respectively. The residual ABPC concentrations were ≤1.18 ng/g for the muscle, ≤0.53 ng/g for the kidney and ≤1.93 ng/g for the intestine, suggesting below the Japanese provisional maximum residue limits. These results reveal that the analytical method is developed for residual ABPC and that the withdrawal period is appropriate.     

氨苄青霉素单抗鉴定与酶联免疫检测方法的初步研究

利用碳化二亚胺(EDC)法将氨苄青霉素(AMP)与匙孔嘁血蓝蛋白(m cKLH)偶联制备免疫原免疫Balb/c小鼠,应用杂交瘤技术将免疫鼠脾细胞与小鼠骨髓瘤细胞(SP2/0)融合,建立分泌氨苄青霉素单克隆抗体的杂交瘤细胞株。杂交瘤细胞染色体数目为97~104条,3D12株亚型为IgG2 a,用其制备的腹水ELISA效价达到2×106。亲和常数为3×10-10mol/L,抗体相对分子质量为1.54×105,与其他抗生素的交叉反应率小于0.01%。采用间接竞争ELISA方法建立检测AMP的标准曲线,在0.5~100 ng/mL范围内呈线形相关,回归方程为Y=0.056 9X+0.130 8,相关指数R2=0.994 8,以10%抑制率对应的浓度计算,该方法对AMP的检测限为0.3 ng/mL,对市售消毒纯牛奶模拟样品最低检测限为0.4 ng/mL。     

A comparison of the effect of short-acting and long-acting cloxacillin-based dry-cow therapy on somatic cell counts after calving in cows also given internal teat sealants

AIM: To compare, in cows treated with an internal teat sealant, the effect of short-acting and long-acting cloxacillin-based dry-cow therapy on somatic cell counts (SCC) after calving.

METHODS: Cows from a spring-calving, pasture-based dairy farm in the Manawatu-Whanganui region of New Zealand were randomly allocated to receive either a short-acting cloxacillin and ampicillin dry-cow therapy and internal teat sealant (n=291) or a long-acting cloxacillin and ampicillin dry-cow therapy and internal teat sealant (n=288) at the end of lactation. Cows were managed on-farm with routine husbandry procedures through the dry period and following calving. A multivariable logistic regression model was used to determine the association between length of action of dry-cow therapy and the proportion of cows with a SCC >150,000?cells/mL at the first herd test after calving.

RESULTS: Age of cow, mean SCC for the preceding season and interval from calving to the first post-calving herd test were all associated with the proportion of cows with an individual SCC >150,000?cells/mL at the first herd test (p<0.001) Treatment with the short-acting dry-cow therapy was not associated with decreased odds of cows having a SCC >150,000?cells/mL at the first herd test compared with treatment with long-acting dry-cow therapy (OR=0.724; 95% CI=0.40–1.30).

CONCLUSIONS AND CLINICAL RELEVANCE: In this herd, which routinely used internal teat sealants, the use of short-acting cloxacillin-based dry-cow therapy did not result in an increased proportion of cows with elevated SSC post-calving. This was a single farm, single year study but indicates that in this herd, changing from a long-acting to a short-acting antimicrobial may have no impact on the prevalence of subclinical mastitis.     

条斑紫菜壳孢子的抗生素敏感性研究

以往研究紫菜细胞对抗生素的敏感性时,常以叶状体的酶解单离体细胞为材料,但由于来自同一个叶状体的体细胞处于不同的分化阶段,离体培养时,体细胞的成活、再生和发育途径均不相同,从而无法准确地判断抗生素对紫菜离体细胞的生长和发育影响。以成活、萌发和发育途径等几乎一致的条斑紫菜壳孢子为研究材料,较系统地观察了3种抗生素对壳孢子的成活、生长和发育的影响。结果表明：卡那霉素能促进条斑紫菜壳孢子的萌发、生长和发育。加卡那霉素培养7 d,26%的壳孢子萌发体,其细胞数多于20个,比对照组多2倍,培养11 d和18 d,萌发体的平均长度分别为对照组的1.6倍和2.1倍。氨苄青霉素能显著地抑制条斑紫菜的壳孢子萌发、生长和发育,造成细胞的分裂速度减缓、叶状体发育异常。加氨苄青霉素培养7 d,80%的壳孢子萌发体的细胞数少于15个,培养11 d和18 d,各试验组的壳孢子萌发体的平均长度均显著低于对照组,并且随着氨苄青霉素浓度的提高,萌发体的平均长度下降。氯霉素对条斑紫菜的壳孢子具有强烈的致死作用。加氯霉素培养7 d,浓度大于100 μg/mL的各试验组的壳孢子萌发体全部死亡;培养11 d,低浓度组（50 μg/mL）的萌发体也全部死亡,90%以上的萌发体的细胞数小于5个。由此得出,氯霉素是开展条斑紫菜基因工程的理想抗性选择压力。     

Skin sensitivity to tuberculins in cattle vaccinated against Johne's disease

Aim: To evaluate the efficacy of a dry-cow antibiotic preparation containing cloxacillin plus ampicillin in a formulation that gives a 10-week duration of action, in comparison to products containing cephalonium (10-week action) or cloxacillin alone (7-week action).

Methods: A total of 493 cows were selected from 6 spring-calving dairy herds in the Manawatu region of New Zealand, according to the criteria of the SAMM plan, to receive intramammary antibiotic therapy at the end of lactation (drying off). Cows were randomly allocated to receive 1 of the 3 dry-cow antibiotic products under investigation. Cows were examined twice during the dry period and twice daily during the first 10 days of their subsequent lactation for the presence of mastitis. Milk samples were collected from individual quarters at the time of drying off and at 7 and 28-35 days after calving, for determination of milk somatic cell counts (SCC). Bacteriology was carried out on milk samples taken from cows that developed mastitis during the first 10 days after calving.

Results: No cows developed mastitis during the dry period. Sixteen cows developed clinical mastitis within 10 days of calving; there was no difference in incidence between treatments. Streptococcus uberis was the most commonly isolated organism. Mean SCC on Day 7 were lower (p = 0.019) in cephalonium-treated quarters (189.9 ± 28.4 × 10³ cells/ml) than in cloxacillin-treated quarters (388.7 ± 71.2 x 10³ cells/ml); values in quarters receiving cloxacillin plus ampicillin were intermediate (252.0 ± 47.0 × 10³ cells/ml). SCC were similar between treatment groups on Day 28–35.

Conclusions: The use of a combination of cloxacillin plus ampicillin was effective for the prevention of mastitis during the dry- and peri-calving-periods in pastured dairy cattle.     

氨苄青霉素在猪和鸡组织残留的微生物测定法研究

以藤黄八叠球菌为工作菌,用杯碟法测定氨苄青霉素在猪和肉鸡组织中的残留。结果表明,氨苄青霉素在磷酸盐缓冲液,肌肉和脂肪,肝脏和肾脏中的最低检测限分别为０．００１２５μｇ／ｍｌ,０．００６２５μｇ／ｇ,０．０１２５μｇ／ｇ。标准曲线的工作范围为０．００１２５,０．００２５,０．００５,０．为,０．０２μｇ／ｍｌ。     

高效液相色谱荧光检测法同时检测鸡血浆中阿莫西林和氨苄西林残留

建立高效液相色谱荧光法同时检测鸡血浆中阿莫西林和氨苄西林的残留量。鸡血浆经乙腈提取,饱和二氯甲烷萃取,酸性条件下水杨醛沸水浴衍生化后,以0.01mol/L的磷酸二氢钾溶液（A）和乙腈溶液（B）为流动相,梯度洗脱,流速为1.0mL/min,荧光检测激发波长为354nm,发射波长为445nm。阿莫西林和氨苄西林线性范围均为5.0~5 000.0μg/L,线性关系良好（r=0.999 9,0.999 6）。当阿莫西林和氨苄西林添加水平均为5.0~125.0mg/L时,鸡血浆样品平均回收率均高于74.72%,相对标准偏差（RSD）均低于8.65%,日内相对标准偏差分别低于4.99%和10.60%,日间相对标准偏差分别低于7.98%和11.29%。测定鸡血浆样品中AMO的检测限（LODs）为2.0μg/L（S/N=3）、定量限（LOQs）为5.0μg/L（S/N=10）,AMP的检测限为1.0μg/L（S/N=3）、定量限为2.5μg/L（S/N=10）。该方法操作简便、快速,且结果精确、灵敏、可靠,可适用于鸡血浆中阿莫西林、氨苄西林同时提取和检测。     

柑橘黄龙病防控药剂筛选试验初报

为筛选有效防治罹病柑橘植株体内黄龙病菌的药剂,选取6种药剂进行韧皮部输液,利用实时定量PCR对病株体内带菌量进行动态监测以确定相对防效。结果表明,连续施药8个月后,硫酸铜、布罗波尔处理组和对照组带菌量下降了20%~30%,2,2 二溴 3 次氮基丙酰胺、异噻唑啉酮以及氨苄青霉素带菌量减少了80%以上;ZnSO 4处理带菌量下降了65.60%。各观察期内相对防效都超过50%的药剂有2,2－二溴－3－次氮基丙酰胺（≥50%）和氨苄青霉素（≥70%）。相对防效分析表明,施药后8个月1 g/L 2,2 二溴 3 次氮基丙酰胺、异噻唑啉酮、氨苄青霉素相对防效分别达到了89.75%、83.72%和87.27%,初步判断这3种药剂对黄龙病病树有防控效果。     

纳米金核酸适配体HCR放大比色法检测 动物源食品中氨苄青霉素残留

为了检测动物原性食品中氨苄青霉素残留,利用氨苄青霉素与核酸适配体的特异性结合能使其脱离纳米金粒子表面的特性,并利用核酸适配体杂交链式反应(HCR)将信号放大,最终通过检测纳米金溶液吸收光谱的变化建立一种氨苄青霉素残留的高灵敏检测方法.首先对各项反应条件进行优化,筛选出HCR放大纳米金比色法的最优检测方法,优化后的检测方法中,NaC1溶液最优浓度为1 mol·L-1,HCR的最优终浓度为11.5％ (V/V),HCR与纳米金孵育的最优反应条件为37℃、30min.氨苄青霉素的检测范围是0～1.2 μmol· L-1,线性方程为y=0.1636x+0.025,R2=0.9953,最低检测限可达到10 nmol·L-1,在实际样品中的检测回收率是92.30％～103.27％.建立的氨苄青霉素适配体的HCR放大纳米金比色法具有操作简便、反应快速、灵敏度高等优点,可用于氨苄青霉素残留量的快速检测.